# My take on the NVX JAD 900.5 - 5 channel amp



## fcarpio

This is my subjective review.

This is a cheap amp! I think I got mine for under $200 new about 6 months ago. I've had it in mi car since. This amp is driving a set of IA C6 and a pair of SWR-T12's active.

I have used another NVX amp in the past and I had a terrible time with the volume knob being an all or nothing kind of deal. I was told that my gains may have been setup too high, which could be the case. For this amp I am NOT using the bass knob as I have no need for it, I control the sub level through my processor and I am not experiencing this issue.

For being a cheap amp it has worked non stop for six months with absolutely no issues. No noises, no weird stuff at all.

Does it have enough power? That is subjective. To give you and Idea, I drive a car with a V8 engine and an aftermarket muffler, so it is louder than stock. In a highway I can listen to music and totally drown out the muffler at about half volume. So there is a lot of room to get louder. I like my music loud and this amp has power to spare. Some people are concerned about the sub channel not being able to power up subs, not an issue with this amp. I have my gains at just over half and there is plenty of power to shake my rear view mirror. I like my tunes a bit bassy and this amp has no problems.

The amp does not get too hot at all, you can drive it hard for a long time and it will only be a little warm.

Footprint is not the smallest of them all, but it isn't that big either. It can easily fit under the seat of a car.

This amp sounds just as good as other amps I've had in the past. I can tell that when compared to my xtant amps (604x and 1001x, these are the older ones) it has less power. The xtants were very powerful amps. This little amp has just about the same power as my DLS Ultimate A4 and A6. These DLS were big and have just about the same power to my ears. This amp is also more powerful than my Helix Ultimate B2/B4 combo. But I may eventually revert back to the Helix only because they are sexier. This amp is just a black box, nothing pretty about it but it gets the job done.

As far as sound quality goes, I don't know. I honestly can't tell which amp I have owned sounds better than the others. when it comes to tuning my system, this amp will play what ask it to play. Want strong bass? I get strong bass. Want bright highs, I get it. I recently posted a review of the Carbon C6 and the listening was done with this amp. Can this amp play clean and loud? Yes, it can.

Would I recommend this amp? Sure. I think it is awesome bang for the buck and it gets the job done very well.


----------



## metanium

Nce review. Ive literally owned 10 different 5- channel amp over the past 8 years, because I love the idea of 1-amp active solutions. Its just so clean and simple.


----------



## Gibberish

metanium said:


> Nce review. Ive literally owned 10 different 5- channel amp over the past 8 years, because I love the idea of 1-amp active solutions. Its just so clean and simple.


Which one is ya fav?


----------



## metanium

Gibberish said:


> Which one is ya fav?


I have used a bunch of different ones. I'll do my best to run down the good and the bad. Overall, I'd take the NVX over the others, as long as I had a clean unbalanced signal to feed it. I recently bought a new Tundra and want to retain the Factory HU. Unfortunately, if I tap the signal before the factory amp, it's balanced and the NVX won't accept balanced inputs. So my NVX is available if anyone's looking for a great 5-channel.

*Best Overall - NVX JAD900.5*
~Has adequate 3-way crossovers to take a 2-channel input and give you really any low-pass, band-pass, and high-pass you'd want in a vehicle. I've ran sub/mid/tweet -and- sub/mid-bass/wide-band on this amp with great success. Also has a subsonic filter, which is a must if you use ported subs.

*Runner-up - TIE-JL Audio XD1000/5v2 & XD700/5v2*
~They have adequate 3-way crossovers to take a 2-channel input and give you really any low-pass, band-pass, and high-pass you'd want in a vehicle. I've ran sub/mid/tweet -and- sub/mid-bass/wide-band on each of these amps with great success. No subsonis filter, but the JL's will accept balanced differential inputs, while the NVX only accepts unbalanced inputs.

*Best sounding - Zuki Hybrid 5-Channel*
~Some will debate that all amps sound the same. All I can say is that my truck never sounded so musical. Not a flexible crossover, so as long as you have external processing you should be good.

Others used:
JBL GTO-5EZ ~ Lots of clean power, not a flexible crossover.
JL Audio HD900/5 ~ Lots of clean power, not a flexible crossover.
JL Audio 500/5 ~ Not enough power on sub, big, but old & sexy.
Audison SR5 ~ Not enough power, somewhat flexible crossover, complicated setup.
Alpine MRV-75 ~ Not enough power, not a flexible crossover.
Alpine PDX-5 ~ Had some noise issues, snap, crackle, pop!
US Amps AX5600 ~ Never worked correctly.


----------



## Swaglife81

metanium said:


> I have used a bunch of different ones. I'll do my best to run down the good and the bad. Overall, I'd take the NVX over the others, as long as I had a clean unbalanced signal to feed it. I recently bought a new Tundra and want to retain the Factory HU. Unfortunately, if I tap the signal before the factory amp, it's balanced and the NVX won't accept balanced inputs. So my NVX is available if anyone's looking for a great 5-channel.
> 
> *Best Overall - NVX JAD900.5*
> ~Has adequate 3-way crossovers to take a 2-channel input and give you really any low-pass, band-pass, and high-pass you'd want in a vehicle. I've ran sub/mid/tweet -and- sub/mid-bass/wide-band on this amp with great success. Also has a subsonic filter, which is a must if you use ported subs.
> 
> *Runner-up - TIE-JL Audio XD1000/5v2 & XD700/5v2*
> ~They have adequate 3-way crossovers to take a 2-channel input and give you really any low-pass, band-pass, and high-pass you'd want in a vehicle. I've ran sub/mid/tweet -and- sub/mid-bass/wide-band on each of these amps with great success. No subsonis filter, but the JL's will accept balanced differential inputs, while the NVX only accepts unbalanced inputs.
> 
> *Best sounding - Zuki Hybrid 5-Channel*
> ~Some will debate that all amps sound the same. All I can say is that my truck never sounded so musical. Not a flexible crossover, so as long as you have external processing you should be good.
> 
> Others used:
> JBL GTO-5EZ ~ Lots of clean power, not a flexible crossover.
> JL Audio HD900/5 ~ Lots of clean power, not a flexible crossover.
> JL Audio 500/5 ~ Not enough power on sub, big, but old & sexy.
> Audison SR5 ~ Not enough power, somewhat flexible crossover, complicated setup.
> Alpine MRV-75 ~ Not enough power, not a flexible crossover.
> Alpine PDX-5 ~ Had some noise issues, snap, crackle, pop!
> US Amps AX5600 ~ Never worked correctly.


I recently went with the JAD900.5 have not installed it because the speakers I want are on back order. I'm excited about this amp. All my processing will be from my Pioneer. I agree all amps don't sound the same by any means. People that try different combos in the same car and listen to the same songs can tell. I know one day I was at my friends house back about 10 years ago and had 2 Fosgate P3's, JL W6 10, 2 Pioneer 12's, 2 different Kenwood amps, 1 Fosgate amp and a few other things. It was a day I was just swapping stuff in and out playing with gains, EQ just to hear the differences in the same 2 or 3 songs. And everything was just different, at least to my ears. One setup could sound cleaner, one could get louder, so on and so on. So now that I'm older and been around the block, I try to be very critical of my buying decisions, especially on a budget going after a $225 amp rather than a high dollar $1000 amp.


----------



## PPI_GUY

I have used (briefly) the Polk Audio variant of the NVX 5 channel reviewed here. The Polk's sub channel is stable to 1 ohm and supposedly produces 500 watts at that resistance. It was VERY powerful and compared to its NVX, SoundStream and PPI twins, its cosmetics are my favorite. 
If I were to choose a single-amp solution and wanted to keep my budget around $250-$300 I would probably go with the Polk. If the budget were higher, I'd probably choose the JL Audio XD700/5. 
Another option that I haven't yet heard might be the new JL Audio RD900/5.


----------



## poormansporsche

Been curious about the NVX amps. Price is right. Thanks for the write up. 

cheers

poorman


----------



## DeltaB

My system starts with a NVX JAD 900.5, which internal design and boards are shared by a number of companies, both big name, as well as private and not-so-big vendors. Upon receipt, I opened the case to examine components and solder quality, and found what is ever present in auto amps, and that is signal components, like op-amps and electrolytic caps of poor quality and inexpensive price, seriously degrading the ability of the amp to produce true high-quality sound. There is a HUGE difference between noise, and being-there type of reproduction. Loud isn't better. It's just noisy.

One of these in this amp, was the use of TI's TL072 op amps for all buffering and signal conditioning. This device, produced since the 70's was one of the first JFET op-amps widely used for high-impedance input circuits, and was quickly overshadowed by the NE5532 for audio usage. This $0.37 part is best used to control a variable speed motor, and not audio, since there are numerous selections of much better audio quality. With 18nV of noise, it produces a constant hiss that is audible in the output section. And while it's slew speed is 13V/us, which is considered tabletop radio quality, the most important factor of the TL072, is the phase shift over the audio spectrum, which changes more than 120 degrees over just a few octaves. In fact, when driven at modest voltages, it can change polarity, causing 180 degree cancellation of frequencies. (phase reversal) This is very bad for your audio, in fact, it's unacceptable. Needless to say, the bean-counters, who opted for least cost, gave it to us with no regard to what is given up in audio quality. This is indicative of all amps on the market today, even in the home audio arena. (My high-end Yamaha AVENTAGE RX-A2030 even suffered from this cost cutting oversight in using low-cost poor-performing op-amps)

So what I've done is to use TI's recommended replacement for input designs that have utilized JFET op-amps, like the TL072, using the Burr-Brown OPA-1642. This op-amp brings with it a number of really impressive performance upgrades. One, comparing it to the TL072, who's THD was 0.003%, with the new, gains me a very impressive 0.00005% total THD, with less than 1/4 of the noise. It's slew rate is almost double of that of the TL072, and gets into the 20V/us slew rate, which can handle complex audio without losing detail. It takes less current to run it, and makes a good drop in replacement without having to redesign the circuit. The real advantage to this change, comes from the most important factor, and that is phase. Your ears are incredibly sensitive to phase, and audio phase is one of the most important things in creating sinusoidal waves that sound "real". The OPA-1642 is phase stable (no shift) throughout the entire audio spectrum all the way up into the MHz range. The soundstage with the new op-amps is nothing short of incredible, and places it in a performance category with some of the finest home audio out there. Channel separation went from around 90dB of separation to almost 130dB, and CMRR went from -86dB to -128dB. Talk about now having an extremely quiet, and low distortion amp. Mono blocks don't perform better than this folks.

All of the signal electrolytic caps were replaced with ELNA's SILMIC II silks, which has become the defacto-standard of audio signal caps these days, and bring with them a very warm and inviting sound.

All of this was done with a little rework time and less than $50. Now, this $250 investment can rival performance of amps 10 times it's cost. The finest investment one can make in their car audio systems, is the attention to detail in the input section of their amplifier, and since all amps suffer this, is the first place to spend attention to really create a soundstage in your vehicle that will rival any out there. It's all about making a correctly phased and uncolored sinusoidal wave for your ear. The manufacturer's bean-counter ripped you off.


----------



## disconnected

I enjoy my Soundstream T5.2500DL 5-channel amp. It is huge, lots of crossover flexibility, 100AMP fuse.


----------



## fcarpio

DeltaB said:


> My system starts with a NVX JAD 900.5, which internal design and boards are shared by a number of companies, both big name, as well as private and not-so-big vendors. Upon receipt, I opened the case to examine components and solder quality, and found what is ever present in auto amps, and that is signal components, like op-amps and electrolytic caps of poor quality and inexpensive price, seriously degrading the ability of the amp to produce true high-quality sound. There is a HUGE difference between noise, and being-there type of reproduction. Loud isn't better. It's just noisy.
> 
> One of these in this amp, was the use of TI's TL072 op amps for all buffering and signal conditioning. This device, produced since the 70's was one of the first JFET op-amps widely used for high-impedance input circuits, and was quickly overshadowed by the NE5532 for audio usage. This $0.37 part is best used to control a variable speed motor, and not audio, since there are numerous selections of much better audio quality. With 18nV of noise, it produces a constant hiss that is audible in the output section. And while it's slew speed is 13V/us, which is considered tabletop radio quality, the most important factor of the TL072, is the phase shift over the audio spectrum, which changes more than 120 degrees over just a few octaves. In fact, when driven at modest voltages, it can change polarity, causing 180 degree cancellation of frequencies. (phase reversal) This is very bad for your audio, in fact, it's unacceptable. Needless to say, the bean-counters, who opted for least cost, gave it to us with no regard to what is given up in audio quality. This is indicative of all amps on the market today, even in the home audio arena. (My high-end Yamaha AVENTAGE RX-A2030 even suffered from this cost cutting oversight in using low-cost poor-performing op-amps)
> 
> So what I've done is to use TI's recommended replacement for input designs that have utilized JFET op-amps, like the TL072, using the Burr-Brown OPA-1642. This op-amp brings with it a number of really impressive performance upgrades. One, comparing it to the TL072, who's THD was 0.003%, with the new, gains me a very impressive 0.00005% total THD, with less than 1/4 of the noise. It's slew rate is almost double of that of the TL072, and gets into the 20V/us slew rate, which can handle complex audio without losing detail. It takes less current to run it, and makes a good drop in replacement without having to redesign the circuit. The real advantage to this change, comes from the most important factor, and that is phase. Your ears are incredibly sensitive to phase, and audio phase is one of the most important things in creating sinusoidal waves that sound "real". The OPA-1642 is phase stable (no shift) throughout the entire audio spectrum all the way up into the MHz range. The soundstage with the new op-amps is nothing short of incredible, and places it in a performance category with some of the finest home audio out there. Channel separation went from around 90dB of separation to almost 130dB, and CMRR went from -86dB to -128dB. Talk about now having an extremely quiet, and low distortion amp. Mono blocks don't perform better than this folks.
> 
> All of the signal electrolytic caps were replaced with ELNA's SILMIC II silks, which has become the defacto-standard of audio signal caps these days, and bring with them a very warm and inviting sound.
> 
> All of this was done with a little rework time and less than $50. Now, this $250 investment can rival performance of amps 10 times it's cost. The finest investment one can make in their car audio systems, is the attention to detail in the input section of their amplifier, and since all amps suffer this, is the first place to spend attention to really create a soundstage in your vehicle that will rival any out there. It's all about making a correctly phased and uncolored sinusoidal wave for your ear. The manufacturer's bean-counter ripped you off.


There is a niche business opportunity for you if you are interested. I would love to see some sort of AB comparison between the original amp and the one you modified.


----------



## DeltaB

fcarpio said:


> There is a niche business opportunity for you if you are interested. I would love to see some sort of AB comparison between the original amp and the one you modified.


I know that finding folks who do rework is rather far and few between. The investment in SMD rework equipment can be rather expensive.

I wouldn't mind seeing an A/B comparison and listening test, but I have the luxury of having listened myself. It does make a marked difference.


----------



## Victor_inox

DeltaB said:


> My system starts with a NVX JAD 900.5, which internal design and boards are shared by a number of companies, both big name, as well as private and not-so-big vendors. Upon receipt, I opened the case to examine components and solder quality, and found what is ever present in auto amps, and that is signal components, like op-amps and electrolytic caps of poor quality and inexpensive price, seriously degrading the ability of the amp to produce true high-quality sound. There is a HUGE difference between noise, and being-there type of reproduction. Loud isn't better. It's just noisy.
> 
> One of these in this amp, was the use of TI's TL072 op amps for all buffering and signal conditioning. This device, produced since the 70's was one of the first JFET op-amps widely used for high-impedance input circuits, and was quickly overshadowed by the NE5532 for audio usage. This $0.37 part is best used to control a variable speed motor, and not audio, since there are numerous selections of much better audio quality. With 18nV of noise, it produces a constant hiss that is audible in the output section. And while it's slew speed is 13V/us, which is considered tabletop radio quality, the most important factor of the TL072, is the phase shift over the audio spectrum, which changes more than 120 degrees over just a few octaves. In fact, when driven at modest voltages, it can change polarity, causing 180 degree cancellation of frequencies. (phase reversal) This is very bad for your audio, in fact, it's unacceptable. Needless to say, the bean-counters, who opted for least cost, gave it to us with no regard to what is given up in audio quality. This is indicative of all amps on the market today, even in the home audio arena. (My high-end Yamaha AVENTAGE RX-A2030 even suffered from this cost cutting oversight in using low-cost poor-performing op-amps)
> 
> So what I've done is to use TI's recommended replacement for input designs that have utilized JFET op-amps, like the TL072, using the Burr-Brown OPA-1642. This op-amp brings with it a number of really impressive performance upgrades. One, comparing it to the TL072, who's THD was 0.003%, with the new, gains me a very impressive 0.00005% total THD, with less than 1/4 of the noise. It's slew rate is almost double of that of the TL072, and gets into the 20V/us slew rate, which can handle complex audio without losing detail. It takes less current to run it, and makes a good drop in replacement without having to redesign the circuit. The real advantage to this change, comes from the most important factor, and that is phase. Your ears are incredibly sensitive to phase, and audio phase is one of the most important things in creating sinusoidal waves that sound "real". The OPA-1642 is phase stable (no shift) throughout the entire audio spectrum all the way up into the MHz range. The soundstage with the new op-amps is nothing short of incredible, and places it in a performance category with some of the finest home audio out there. Channel separation went from around 90dB of separation to almost 130dB, and CMRR went from -86dB to -128dB. Talk about now having an extremely quiet, and low distortion amp. Mono blocks don't perform better than this folks.
> 
> All of the signal electrolytic caps were replaced with ELNA's SILMIC II silks, which has become the defacto-standard of audio signal caps these days, and bring with them a very warm and inviting sound.
> 
> All of this was done with a little rework time and less than $50. Now, this $250 investment can rival performance of amps 10 times it's cost. The finest investment one can make in their car audio systems, is the attention to detail in the input section of their amplifier, and since all amps suffer this, is the first place to spend attention to really create a soundstage in your vehicle that will rival any out there. It's all about making a correctly phased and uncolored sinusoidal wave for your ear. The manufacturer's bean-counter ripped you off.


 I agree with everything said here. front stage is what creates amplifier sound signature.


----------



## EricP72

So...if I was to purchase a pair of these amps...who would I go to have the upgrades done? I agree with what was said but I don't have the connections to have it done.


----------



## DeltaB

manish said:


> So...if I was to purchase a pair of these amps...who would I go to have the upgrades done? I agree with what was said but I don't have the connections to have it done.


Well, finding a repair shop isn't all that hard. (Google is your friend) There are numerous facilities across the nation who can do repair/mods to car audio amps. You obviously would have to see if they work with surface mount, (which most do) describe what you are looking to do, and then negotiate a price.


----------



## Swaglife81

My only concern with this amp is can it really power a SQ sub like a IDQ12 or Dayton HO 12. Anyone have opinions and ran it on 1 of those subs or something similar


----------



## kmbkk

I just ordered one of these for my son's car (97 Miata). It's replacing 2 old school Rockford amps. I'll report back once i get it installed!


----------



## FaintReality

DeltaB said:


> manish said:
> 
> 
> 
> So...if I was to purchase a pair of these amps...who would I go to have the upgrades done? I agree with what was said but I don't have the connections to have it done.
> 
> 
> 
> Well, finding a repair shop isn't all that hard. (Google is your friend) There are numerous facilities across the nation who can do repair/mods to car audio amps. You obviously would have to see if they work with surface mount, (which most do) describe what you are looking to do, and then negotiate a price.
Click to expand...

Did you do the work yourself or have someone do it for you? Where would one buy the replacement parts? 

I just purchased the JAD800.4 & JAD1200.1 a few days ago and would be willing to pay if it makes the difference as stated.


----------



## EricP72

I would look for a shop but I would need a break down of everything that was suggested and the part numbers. I swear I'd buy a pair of these 5 channel and call it a day. Also Deltab I would some gut shots of your modified amp. This is something I'm really considering.


----------



## DeltaB

FaintReality said:


> Did you do the work yourself or have someone do it for you? Where would one buy the replacement parts?
> 
> I just purchased the JAD800.4 & JAD1200.1 a few days ago and would be willing to pay if it makes the difference as stated.


Answering the question of doing it myself, yes, I do my own work. And while there are various sources for parts, I use Mouser when I can. This is the device that I chose for this project and can be purchased in quantities as small as 1. For this project I purchased 10, which is roughly $30 for the op-amps.

http://www.mouser.com/ProductDetail/Texas-Instruments/OPA1642AIDR/?qs=sGAEpiMZZMtxdzBvM0rKcTv7Ysc73uR4Hw9tGvON1jU%3d

This is the most important component, since TL072's should never have been chosen and has no place in audio amps, especially for low frequency. The capacitors are a personal choice from my own personal experience, and also a very worthwhile part of this upgrade recommendation. All signal caps which the actual analogue signal passes is the object of attention. Various capacitance is used, but the most frequent one you'll need is 10uF and don't use less than 16v rating in the signal path. They will run you about 0.20~0.30 USD each, depending on quantity you purchase.

http://www.mouser.com/ProductDetail/Elna/RFS-35V100ME35/?qs=sGAEpiMZZMtZ1n0r9vR22Vaq1AHMe%252bCMT8zUcxzUcsM%3d

If I didn't use ELNA SilMic II, I would choose Nichicon Muse. Both specifically designed for audio usage, and it shows when used compared to the originals.

For me, audio sound quality has always been the primary focus when selecting components to be used in my projects, and for a Class D auto audio amp, this platform is a pretty good start. The power supply section is adequate, the gate driver and MOSFET output section is well thought out and a viable platform to really enjoy some great sound from your vehicle. Overall, I'm very pleased with this upgraded choice to my XJ8 sound system.


----------



## EricP72

I wonder if the Hertz version of this amp has the upgraded caps and op amps.


----------



## norurb

manish said:


> I wonder if the Hertz version of this amp has the upgraded caps and op amps.


I know Zapco has the ST-2xSQ and ST-4xSQ, both with upgraded opamps and caps. The 2ch isn't on Atrend just yet but I'm watching and waiting. If they don't hurry I'll order up a nvx jad900.5 and do the upgrades myself.


----------



## EricP72

Good idea. I'm currently trying to find a place or person to perform these upgrades for me. If anybody locate a place let me know.


----------



## FaintReality

Looks like this is just a matter of desauldering and resauldering? Any shop recommendations in Southern California?

Are the mentioned cap replacements needed if using an external DSP and running the amp full range?


----------



## DC/Hertz

I really want to try the ST-4SQ but I don't know about cutting my power in half. I do like it loud from time to time when the windows are down on the high way.


----------



## DeltaB

norurb said:


> I know Zapco has the ST-2xSQ and ST-4xSQ, both with upgraded opamps and caps. The 2ch isn't on Atrend just yet but I'm watching and waiting. If they don't hurry I'll order up a nvx jad900.5 and do the upgrades myself.


Concerning Zapco's offerings, the Z-LX series amps (Class A/B) which they have spent time improving on input section to offer high SQ will certainly cost you well over a grand, and as I stated before, if you have the ability, you can do a little rework and rival SQ of offerings 10 times the original price of NVX. And while I understand that rework may be beyond the abilities of some here, it's a DIY project well worth the time. Even Zapco recognizes the sonic benefits of using ELNA SilMic II's in their platform. Make sure you don't deviate from TI's strongly recommended replacement for the TL072 with Burr-Brown OPA1642's and you'll love yourself for it.

Just be mindful, only the Z-LX series uses the upper-end caps and op-amps, (in fact, the OPA1642 is actually better performing in many critical areas than the AD OP275 used in the Z-LX) and the SQ models uses the late 70's bi-polar NE5532, (which is actually on the lower level of performance compared to it's contemporaries) and no ELNA SilMic's.


----------



## EricP72

DeltaB said:


> Concerning Zapco's offerings, the Z-LX series amps (Class A/B) which they have spent time improving on input section to offer high SQ will certainly cost you well over a grand, and as I stated before, if you have the ability, you can do a little rework and rival SQ of offerings 10 times the original price of NVX. And while I understand that rework may be beyond the abilities of some here, it's a DIY project well worth the time. Even Zapco recognizes the sonic benefits of using ELNA SilMic II's in their platform. Make sure you don't deviate from TI's strongly recommended replacement for the TL072 with Burr-Brown OPA1642's and you'll love yourself for it.


Thank you to DeltaB. For those who are not sure what to order i have included my order sheet. Now my qty is for 2 amplifiers modifications, so just cut my qty in half for 1 amp. Now i'm searching for a shop to perform these upgrades.


----------



## norurb

Check with theamplab.net, not sure if they are willing.


----------



## FaintReality

Zed Audio may as well - http://www.zedaudiocorp.com/service.html


----------



## EricP72

norurb said:


> Check with theamplab.net, not sure if they are willing.


Thanks, I just sent them a RFQ. I will await there response.


***Update*** was quoted $75 a amp.


----------



## norurb

manish said:


> Thanks, I just sent them a RFQ. I will await there response.
> 
> 
> ***Update*** was quoted $75 a amp.


Will they allow you to supply the parts?


----------



## EricP72

Yep.


----------



## EricP72

"Eric,

I assume you've done your research to confirm this will indeed work. 
I believe $75 per amp seems appropriate for this amount of work. If this works for you, let me know and we can move forward.
Thank you,
Ethan Poissonnier
Co-Owner - Head of Sales - Public Relations
On 8/28/2017 2:50 PM, The Amp Lab wrote:
The Amp Lab
The Amp Lab
Phone: (207) 313-6236
Fax:
Name: Eric Perry
Email: [email protected]
Subject: Amplifier 
I would like to submit a RFQ for a simple amp modification. I want to have all 30 signal electrolytic caps replaced with ELNA's SILMIC II silks. And all 10 JFET op-amp TL072, replaced with the Burr-Brown OPA-1642. Basically upgrading the front stage. I will supply the components, I just want to know the labor cost. 

Amp: NVX JAD 900.5
QTY: 2
Upgraded OP-amp: OPA1642AIDR
QTY: 10 per amplifier
Upgraded 10uF Cap: Aluminum Electrolytic Capacitors - Leaded 10uF 35V 20% Audio SILMIC II
QTY: 20 per amplifier
Upgraded 22uF Cap: Aluminum Electrolytic Capacitors - Leaded 22uF 35V 20% Audio SILMIC II
QTY: 10 per amplifier

---
Thank you for using our services
The Amp Lab"


----------



## norurb

Great info, thanks.


----------



## DeltaB

manish said:


> "Eric,
> 
> I assume you've done your research to confirm this will indeed work.
> I believe $75 per amp seems appropriate for this amount of work. If this works for you, let me know and we can move forward.
> Thank you,
> Ethan Poissonnier
> Co-Owner - Head of Sales - Public Relations
> On 8/28/2017 2:50 PM, The Amp Lab wrote:
> The Amp Lab
> The Amp Lab
> Phone: (207) 313-6236
> Fax:
> Name: Eric Perry
> Email: [email protected]
> Subject: Amplifier
> I would like to submit a RFQ for a simple amp modification. I want to have all 30 signal electrolytic caps replaced with ELNA's SILMIC II silks. And all 10 JFET op-amp TL072, replaced with the Burr-Brown OPA-1642. Basically upgrading the front stage. I will supply the components, I just want to know the labor cost.
> 
> Amp: NVX JAD 900.5
> QTY: 2
> Upgraded OP-amp: OPA1642AIDR
> QTY: 10 per amplifier
> Upgraded 10uF Cap: Aluminum Electrolytic Capacitors - Leaded 10uF 35V 20% Audio SILMIC II
> QTY: 20 per amplifier
> Upgraded 22uF Cap: Aluminum Electrolytic Capacitors - Leaded 22uF 35V 20% Audio SILMIC II
> QTY: 10 per amplifier
> 
> ---
> Thank you for using our services
> The Amp Lab"


Just for you and Amp Lab's concern, here is something for your viewing pleasure concerning the proper selection of op amps for this modification.

https://e2e.ti.com/support/amplifiers/precision_amplifiers/w/design_notes/upgrading-op-amps-in-audio-equipment


----------



## dsw1204

DeltaB said:


> My system starts with a NVX JAD 900.5, which internal design and boards are shared by a number of companies, both big name, as well as private and not-so-big vendors. Upon receipt, I opened the case to examine components and solder quality, and found what is ever present in auto amps, and that is signal components, like op-amps and electrolytic caps of poor quality and inexpensive price, seriously degrading the ability of the amp to produce true high-quality sound. There is a HUGE difference between noise, and being-there type of reproduction. Loud isn't better. It's just noisy.
> 
> One of these in this amp, was the use of TI's TL072 op amps for all buffering and signal conditioning. This device, produced since the 70's was one of the first JFET op-amps widely used for high-impedance input circuits, and was quickly overshadowed by the NE5532 for audio usage. This $0.37 part is best used to control a variable speed motor, and not audio, since there are numerous selections of much better audio quality. With 18nV of noise, it produces a constant hiss that is audible in the output section. And while it's slew speed is 13V/us, which is considered tabletop radio quality, the most important factor of the TL072, is the phase shift over the audio spectrum, which changes more than 120 degrees over just a few octaves. In fact, when driven at modest voltages, it can change polarity, causing 180 degree cancellation of frequencies. (phase reversal) This is very bad for your audio, in fact, it's unacceptable. Needless to say, the bean-counters, who opted for least cost, gave it to us with no regard to what is given up in audio quality. This is indicative of all amps on the market today, even in the home audio arena. (My high-end Yamaha AVENTAGE RX-A2030 even suffered from this cost cutting oversight in using low-cost poor-performing op-amps)
> 
> So what I've done is to use TI's recommended replacement for input designs that have utilized JFET op-amps, like the TL072, using the Burr-Brown OPA-1642. This op-amp brings with it a number of really impressive performance upgrades. One, comparing it to the TL072, who's THD was 0.003%, with the new, gains me a very impressive 0.00005% total THD, with less than 1/4 of the noise. It's slew rate is almost double of that of the TL072, and gets into the 20V/us slew rate, which can handle complex audio without losing detail. It takes less current to run it, and makes a good drop in replacement without having to redesign the circuit. The real advantage to this change, comes from the most important factor, and that is phase. Your ears are incredibly sensitive to phase, and audio phase is one of the most important things in creating sinusoidal waves that sound "real". The OPA-1642 is phase stable (no shift) throughout the entire audio spectrum all the way up into the MHz range. The soundstage with the new op-amps is nothing short of incredible, and places it in a performance category with some of the finest home audio out there. Channel separation went from around 90dB of separation to almost 130dB, and CMRR went from -86dB to -128dB. Talk about now having an extremely quiet, and low distortion amp. Mono blocks don't perform better than this folks.
> 
> All of the signal electrolytic caps were replaced with ELNA's SILMIC II silks, which has become the defacto-standard of audio signal caps these days, and bring with them a very warm and inviting sound.
> 
> All of this was done with a little rework time and less than $50. Now, this $250 investment can rival performance of amps 10 times it's cost. The finest investment one can make in their car audio systems, is the attention to detail in the input section of their amplifier, and since all amps suffer this, is the first place to spend attention to really create a soundstage in your vehicle that will rival any out there. It's all about making a correctly phased and uncolored sinusoidal wave for your ear. The manufacturer's bean-counter ripped you off.



I wonder if anyone could go to a manufacturer and make a custom order with the changes that you made. Do you think a manufacturer would make those alterations (that you did) in a special order? This way, maybe someone could get that upgraded amp and keep the manufacturer's warranty...maybe.


----------



## EricP72

No. Those Amps are made overseas and shipped here.


----------



## dsw1204

manish said:


> No. Those Amps are made overseas and shipped here.


I really wasn't expecting a positive reply, just hoping. There is one manufacturer who makes in the U.S.. MMATS, but their prices are pretty high to begin with.


----------



## FaintReality

What is the difference between the OPA1642AIDR / AID / AIDGKR / AIDGKT?


----------



## DeltaB

FaintReality said:


> What is the difference between the OPA1642AIDR / AID / AIDGKR / AIDGKT?


Package sizes and body type. You can reference the end of datasheet to see the difference. For this amp you want AIDR or AID. GK is much smaller VSSOP package. You need SOIC-8 body.

http://www.ti.com/lit/ds/symlink/opa1642.pdf


----------



## EricP72

Is there any modification you recommend with the power supply? or do you think its pretty stout as is?


----------



## fcarpio

This is a very cool concept, but an amp that is a great "base" for upgrading and then upgrade the parts that need to go. I wonder if this is as straight forward as it seems because there is a lot of engineering that goes into this things. Is something as simple as changing some parts will make a "positive" difference? It would also be nice if whomever is upgrading this amp could do some sort of A/B test of the before and after to see what kind of differences we are looking at.


----------



## rton20s

dsw1204 said:


> I wonder if anyone could go to a manufacturer and make a custom order with the changes that you made. Do you think a manufacturer would make those alterations (that you did) in a special order? This way, maybe someone could get that upgraded amp and keep the manufacturer's warranty...maybe.





manish said:


> No. Those Amps are made overseas and shipped here.


If this customization is something you are looking to do, I would follow the path that DeltaB has laid out. If you want to see it at a larger scale, your best bet is to find yourself a pile of cash, find out who the actual amplifier manufacturer is, and meet their minimum order requirements for a run of amps built to your spec. Congratulations, you're in the car audio "manupackturer" business. Good luck with that.


----------



## EricP72

fcarpio said:


> This is a very cool concept, but an amp that is a great "base" for upgrading and then upgrade the parts that need to go. I wonder if this is as straight forward as it seems because there is a lot of engineering that goes into this things. Is something as simple as changing some parts will make a "positive" difference? It would also be nice if whomever is upgrading this amp could do some sort of A/B test of the before and after to see what kind of differences we are looking at.


Normally you are correct. But based on the suggested upgrades, we are using the same value components, just higher quality. So its not like we are adding caps or op-amps. Also it was already done with just the listed mods. I really think your right with a nice comparison though. I plan to do a pair of these 5 channel amps, maybe when i get to it, i can do 1 and then have someone test them or i can do a a/b swap out and provide a more real world comparison. Its been awhile since i did a review so this could be a nice project for this fall. Kinda wish Wldock = Walt was still here in Michigan to have another pair of seasoned ears.


----------



## DeltaB

fcarpio said:


> This is a very cool concept, but an amp that is a great "base" for upgrading and then upgrade the parts that need to go. I wonder if this is as straight forward as it seems because there is a lot of engineering that goes into this things. Is something as simple as changing some parts will make a "positive" difference? It would also be nice if whomever is upgrading this amp could do some sort of A/B test of the before and after to see what kind of differences we are looking at.


It isn't a concept. It is as strait forward in this case, as it has already been done. I own one. There isn't any real magic here.


----------



## willis36

Subbed for future reference. I assume this mod will work with the PPI Phantom series??


----------



## norurb

fcarpio said:


> This is a very cool concept, but an amp that is a great "base" for upgrading and then upgrade the parts that need to go. I wonder if this is as straight forward as it seems because there is a lot of engineering that goes into this things. Is something as simple as changing some parts will make a "positive" difference? It would also be nice if whomever is upgrading this amp could do some sort of A/B test of the before and after to see what kind of differences we are looking at.


A few years back I was providing a service for Nissan SR20DE/DET ecu upgrades. The upgrade involved adding a daughterboard and reflashed eproms. Concept was to take a well engineered oem part and mod it for power upgrades. Point is that oem will get you so far but mods will make it that much better.

Burson Audio has a link that demonstrates the desoldering/soldering for opamp upgrades. Nifty video.


----------



## DeltaB

willis36 said:


> Subbed for future reference. I assume this mod will work with the PPI Phantom series??


I don't have a schematic, so I would actually have to see the amp to comment on what buffers they are using.

Concerning the usage of signal path upgrade caps, that is universal. The reason we use coupling caps before and after the op-amp, is to isolate DC from it's input and protect it's output, and only AC passes. It's a DC block. Since all of the signal going in, and coming out of that buffer circuit through them, it is certainly applicable, and audible.

Concerning the op-amp, if it is using a TI TL072, then yes, you can do a drop in replacement with a Burr-Brown OPA1642. If you were to use SPICE data to construct a buffer with a JFET, you would find the data for gain structure the same, and since you don't have to worry about the need for feedback, like you have to deal with on some bi-polar designs, it makes an easy choice. TL072's have no place in audio circuits. They're slow, noisy, overshoot and invert phase at higher levels.


----------



## Swaglife81

DC/Hertz said:


> I really want to try the ST-4SQ but I don't know about cutting my power in half. I do like it loud from time to time when the windows are down on the high way.


How much power do you need? The ST4X P version is 80x4 instead of 65x4 in the SQ version. If you are worried about mid power bridged 2 channels is more than enough. Unless you would be using this on a sub or 2 than different story.

This might be a dumb question concerning 5 channels as I've never owned one. Specs always list 4ohm and 2 ohm. Can the amp be ran at 2ohms on the sub channel and 4 ohms on the 4 other channels. I was worried about some kind of limitation when wiring this route. I always wire my subs at 1-2 ohm load


----------



## DeltaB

Swaglife81 said:


> How much power do you need? The ST4X P version is 80x4 instead of 65x4 in the SQ version. If you are worried about mid power bridged 2 channels is more than enough. Unless you would be using this on a sub or 2 than different story.
> 
> This might be a dumb question concerning 5 channels as I've never owned one. Specs always list 4ohm and 2 ohm. Can the amp be ran at 2ohms on the sub channel and 4 ohms on the 4 other channels. I was worried about some kind of limitation when wiring this route. I always wire my subs at 1-2 ohm load


While I understand that many want to run subs at 1~2ohm, for SQ it is preferable to run at least 4ohm due to damping factor and output impedance of Class D operation.

From Brian Morelli @ NVX Tech;

Minimum impedance for all channels is 2ohms. You can have different loads on different channels. (4ohm on the fronts/rear, 2ohm on sub). 

The damping factor for all JADs is greater than 200

NVX Tech


----------



## Swaglife81

DeltaB said:


> While I understand that many want to run subs at 1~2ohm, for SQ it is preferable to run at least 4ohm due to damping factor and output impedance of Class D operation.
> 
> From Brian Morelli @ NVX Tech;
> 
> Minimum impedance for all channels is 2ohms. You can have different loads on different channels. (4ohm on the fronts/rear, 2ohm on sub).
> 
> The damping factor for all JADs is greater than 200
> 
> NVX Tech


Thanks, exactly what I wanted to know. It might have been the amps I used in the past but I was running a Fosgate 500x2 at 2 ohms vs 250x2 at 4 ohms but couldn't audibly hear a difference other than SPL. I understand an amp will work harder. I ran that amp for years. Aside from metering differences with various equipment seeing the difference how much difference can someone hear with 2 ohms vs 4 ohms given the same quality and power output is equal?


----------



## DeltaB

Swaglife81 said:


> Thanks, exactly what I wanted to know. It might have been the amps I used in the past but I was running a Fosgate 500x2 at 2 ohms vs 250x2 at 4 ohms but couldn't audibly hear a difference other than SPL. I understand an amp will work harder. I ran that amp for years. Aside from metering differences with various equipment seeing the difference how much difference can someone hear with 2 ohms vs 4 ohms given the same quality and power output is equal?


From Crown Audio Engineers; "Loudspeakers have a mind of their own. You send them a signal and they add their own twist to it. They keep on vibrating after the signal has stopped, due to inertia. That's called "ringing" or "time smearing." In other words, the speaker produces sound waves that are not part of the original signal. Suppose the incoming signal is a "tight" kick drum with a short attack and decay in its signal envelope. When the kick-drum signal stops, the speaker continues to vibrate. The cone bounces back and forth in its suspension. So that nice, snappy kick drum turns into a boomy throb. Fortunately, a power amplifier can exert control over the loudspeaker and prevent ringing. Damping is the ability of a power amplifier to control loudspeaker motion. It's measured in Damping Factor, which is load impedance divided by amplifier output impedance. High damping factor equals tight bass."


----------



## FaintReality

manish said:


> norurb said:
> 
> 
> 
> Check with theamplab.net, not sure if they are willing.
> 
> 
> 
> Thanks, I just sent them a RFQ. I will await there response.
> 
> 
> ***Update*** was quoted $75 a amp.
Click to expand...

Did you send them in yet? Did you contact any other companies for quotes?


----------



## EricP72

I didn't own one. I do have one coming now. Then I will grab another one. Then I plan to send one in have it done, then compare the 2. But I have a lot going on right now at work and at home. I'm thinking I might get the one done and send them to a trusted member to do some testing on them. And I only got a quote back from one place.


----------



## EricP72

Question. In regards to the subwoofer channel x-over can it do full pass. If not what is the highest freq that is allowed on the mono channel? I'm asking because I want to run a active 3 way setup and use the mono channels for the mid-bass drivers. Of course using 2 5 channels.


----------



## norurb

manish said:


> Thank you to DeltaB. For those who are not sure what to order i have included my order sheet. Now my qty is for 2 amplifiers modifications, so just cut my qty in half for 1 amp. Now i'm searching for a shop to perform these upgrades.


I just put in my order to do one amp only. Can't wait to get this done. Thanks.


----------



## metanium

norurb said:


> I just put in my order to do one amp only. Can't wait to get this done. Thanks.


So who are you having do the upgrade? I must have missed it.


----------



## norurb

I'll just do it myself. Hell with it I guess.


----------



## metanium

norurb said:


> I'll just do it myself. Hell with it I guess.


Nice! Please take & post some pics, as I'd love to get the nerve up to try this too.


----------



## norurb

Will do.


----------



## forty5cal1911

Looking forward to that Norurb. I'm looking to do this on my 800.4's and trying to determine if I send it out or do it myself.


----------



## rton20s

I'll start by saying that I think the JAD line from NVX is a great option for budget buyers. And I have recommended them to people asking for amp advice more times than I can count. I'm also all for improvements, but I wonder at what point, do you look at other options if SQ is your primary focus?

As an example, an upgraded JAD800.4 will likely cost you at least $300-325 for the initial amp purchase plus the upgrades if you need someone else to perform the work. Then take into account any addition shipping and you're likely upwards of $400 and probably with no form of warranty. But, you have a better small footprint, powerful, class D amp with a 10.4" x 6.7" footprint. 

I would think depending on how important that small footprint and class D (efficiency) is to you, there may be better ways to spend the money if sound quality is your focus. While not as powerful and becoming harder to come by, the DLS CC-44 is an even smaller (85Wx4 @ 4 Ohms, 9.9"x5.0") class D with a great reputation for SQ. DLS was starting to make inroads in the US again when Chris Bennett was there. Since jumping ship to Audio Control, the brand has become stagnant stateside. The DLS CC-44 can still be had for under $400 to your door from ebay. I am not sure what their US distribution looks like right now.

If you're willing to sacrifice a little space, power and efficiency, there is also the Sony XM-GS4 (70Wx4 @ 4 Ohms, 10.75" x 8") at $250 and the Zapco ST-4X SQ (65Wx4 @ 4 Ohms, 12.6" x 6.3") at $190. Both of these amps have been praised for their sound quality.


----------



## norurb

Great advice. I guess I just like a challenge.


----------



## fcarpio

DeltaB said:


> From Crown Audio Engineers; "Loudspeakers have a mind of their own. You send them a signal and they add their own twist to it. They keep on vibrating after the signal has stopped, due to inertia. That's called "ringing" or "time smearing." In other words, the speaker produces sound waves that are not part of the original signal. Suppose the incoming signal is a "tight" kick drum with a short attack and decay in its signal envelope. When the kick-drum signal stops, the speaker continues to vibrate. The cone bounces back and forth in its suspension. So that nice, snappy kick drum turns into a boomy throb. Fortunately, a power amplifier can exert control over the loudspeaker and prevent ringing. Damping is the ability of a power amplifier to control loudspeaker motion. It's measured in Damping Factor, which is load impedance divided by amplifier output impedance. High damping factor equals tight bass."


So not all amps are the same. I knew it...


----------



## forty5cal1911

norurb said:


> Great advice. I guess I just like a challenge.


Much respect! I'll tell you what I'm pretty ok with a fine tip iron but I wanted to see what I was up against this morning. 

I pulled out an old pbx card that had some SMD op-amps on it. Ran through removing, cleaning and replacing.... Ha! No way I'm doing this for 8 op-amps per amp. Just lining up the legs and traces properly and not moving them considerably during soldering was a major test of my patience.



rton20s said:


> I'll start by saying that I think the JAD line from NVX is a great option for budget buyers. And I have recommended them to people asking for amp advice more times than I can count. I'm also all for improvements, but I wonder at what point, do you look at other options if SQ is your primary focus?


I'm totally in agreement. Depending on what your requirements are I would almost always choose the Zapco. 
In my case I love the clean black cosmetics and size of the NVX and you can't deny the power output of these guys. Compared to the Arc XDi and JL HD's I've heard I can't say that I feel slighted with the NVX.
At roughly $75 in labor per amp, for me, that is well worth it to have someone else do it. I could re-cap this guy all day but replacing op-amps.... now that I've done it first hand my time is worth more than that.

Next amps I plan on buying will be GaN FET based Class D as they get rolled out.


----------



## wr3nchmonkey

This is a very interesting thread. So you're saying I could get an 800.4 and throw a little bit of time and money into it I could have something comparable to an amp in the $1000 range? If I'm understanding this correctly than it would make no sense not to do this. Are there any other components that could be easily upgraded?


----------



## dcfis

It's never that easy but it does what it's supposed to, deliver lots of clean power. It will not cure poor speaker choices out shoddy install which is where you should focus your resources


----------



## wr3nchmonkey

dcfis said:


> It's never that easy but it does what it's supposed to, deliver lots of clean power. It will not cure poor speaker choices out shoddy install which is where you should focus your resources


Assuming high quality drivers are installed professionally. Is upgraded caps and op amps going to make a difference? This would be something i could easily do myself which is why it sparks my interest. I could spent 200 on an amp and 50 on parts. I have all of the tools already due to my profession. Instead of forking over 500 or more for a "high end" amp

Sent from my SM-G920P using Tapatalk


----------



## DeltaB

wr3nchmonkey said:


> Assuming high quality drivers are installed professionally. Is upgraded caps and op amps going to make a difference? This would be something i could easily do myself which is why it sparks my interest. I could spent 200 on an amp and 50 on parts. I have all of the tools already due to my profession. Instead of forking over 500 or more for a "high end" amp
> 
> Sent from my SM-G920P using Tapatalk


The greatest Achilles heel of the audio market is low quality op amps, especially in light of current advances in HU's. The TL072 has no place in audio equipment in light of the choices we have today. One of the selling points for Zapco for example, is certainly true in their marketing for the Z-LX line, where they use AD's OP275's in theirs. The OP275 and the Burr Brown OPA1642 are actually very close in design, with the AD being a through hole, and the OPA1642 SMD only. When you move your design into SMD, you can leverage much better designs for crosstalk, PSRR and CMRR. With open loop gains above 120db, it's dynamic range gets into home audio performance. It is marked and certainly quite audible. I certainly enjoy mine.


----------



## wr3nchmonkey

DeltaB said:


> With open loop gains above 120db, it's dynamic range gets into home audio performance. It is marked and certainly quite audible. I certainly enjoy mine.


So you are using the NVX with upgraded components?

Sent from my SM-G920P using Tapatalk


----------



## dcfis

Highly doubt anyone is doing that and I bet there is smd hell to deal with. He is using end game Zapco


----------



## DeltaB

dcfis said:


> Highly doubt anyone is doing that and I bet there is smd hell to deal with. He is using end game Zapco


I have been modifying and refurbishing high end audio since the 70's. Was at Altec-Lansing in the late 80's and early 90's. There is no end-game other than sound quality.


----------



## bnae38

ELNA developed new raw material for the separate paper which use a silk fibers.
Therefore, this capacitor can give you high grade sound for your audio design.
● Due to the silk fiber's pliability, the capacitor makes a dream of the high quality
sound.
For examples ;
● To relieve the music's vibration energy.
● To decrease the peak feeling sound at high compass and rough quality sound at
middle compass.


Lol. A quality cap is a quality cap... Not sure what they're replacing here but Elna is smoking the good stuff imo..

I'll stick with my Panasonic's 

Opa1642 and 2209 are solid opamps for sure, I keep a stock of both. No argument there. 

I'm more of a measurement (AP or Dscope) guy, listening is... hard to do objectivly. Psychoacoustics is rough. We hear what we want to.

Not suggesting the upgrades are pointless , just trying to keep things in perspective.


----------



## DeltaB

bnae38 said:


> ELNA developed new raw material for the separate paper which use a silk fibers.
> Therefore, this capacitor can give you high grade sound for your audio design.
> ● Due to the silk fiber's pliability, the capacitor makes a dream of the high quality
> sound.
> For examples ;
> ● To relieve the music's vibration energy.
> ● To decrease the peak feeling sound at high compass and rough quality sound at
> middle compass.
> 
> 
> Lol. A quality cap is a quality cap... Not sure what they're replacing here but Elna is smoking the good stuff imo..
> 
> I'll stick with my Panasonic's
> 
> Opa1642 and 2209 are solid opamps for sure, I keep a stock of both. No argument there.
> 
> I'm more of a measurement (AP or Dscope) guy, listening is... hard to do objectivly. Psychoacoustics is rough. We hear what we want to.
> 
> Not suggesting the upgrades are pointless , just trying to keep things in perspective.


For signal path caps, ELNA sounds better than even MUSE. For power supply, I have used Panasonics, and in fact, on my 3000v DC power supply for use in transmitter usage on high frequency, I use Panasonics over Nichicon.


----------



## bnae38

DeltaB said:


> For signal path caps, ELNA sounds better than even MUSE. For power supply, I have used Panasonics, and in fact, on my 3000v DC power supply for use in transmitter usage on high frequency, I use Panasonics over Nichicon.


Well I probably need to keep an open mind . Had more typed out, but meh.


----------



## bnae38

I suppose, i'll get some too for my lab.. cheap enough. If nothing else, i can then say i use them. 

20% irritates me, can hand match though and keep cmrr decent


----------



## MrHarv

Does anyone know if the NVX JAD800.4 is the same when it comes to the opamp replacement, caps etc? 

Sent from my SM-N920P using Tapatalk


----------



## wr3nchmonkey

MrHarv said:


> Does anyone know if the NVX JAD800.4 is the same when it comes to the opamp replacement, caps etc?
> 
> Sent from my SM-N920P using Tapatalk


Well by looking at pictures of the guts on the 800.4 it looks to have the same caps and op amps so I would assume so.


----------



## forty5cal1911

Just cracked mine open to confirm for my order.

The NVX JAD800.4 has:

(10) TL072 op-amps
(16) 10uF 50V caps in the signal path
(8) 22uF 50V caps in the signal path


----------



## wr3nchmonkey

forty5cal1911 said:


> Just cracked mine open to confirm for my order.
> 
> The NVX JAD800.4 has:
> 
> (10) TL072 op-amps
> (16) 10uF 50V caps in the signal path
> (8) 22uF 50V caps in the signal path


You will be upgrading yours?


----------



## forty5cal1911

wr3nchmonkey said:


> You will be upgrading yours?


Yes I am upgrading both of my 800.4's leaving my 1200.1 as is.


----------



## bnae38

If you guys like, i can probably do this for you at a reasonable price. Probably get 1-2 requests per month to fix stuff at random on here lol.


Can even do thdn/freq response/phase testing before and after.. High power supply, non inductive load's, dscope; all the good stuff.

Lmk.. ref's available.


----------



## wr3nchmonkey

forty5cal1911 said:


> Yes I am upgrading both of my 800.4's leaving my 1200.1 as is.


Any chance you will be doing any kind of before and after test? I'd be really interested in what kind of results this will produce.


----------



## rton20s

bnae38 said:


> If you guys like, i can probably do this for you at a reasonable price. Probably get 1-2 requests per month to fix stuff at random on here lol.
> 
> 
> Can even do thdn/freq response/etc testing before and after.. High power supply, non inductive load's, dscope; all the good stuff.
> 
> Lmk.. ref's available.


If you or anyone else performs the upgrade and has before and after measurements, I would be interested in seeing the results posted.


----------



## bnae38

rton20s said:


> If you or anyone else performs the upgrade and has before and after measurements, I would be interested in seeing the results posted.


Going to play around with my ks900.6 after i get the backup/temp replacement 900.6 completed.. paint is drying as we speak.

I have mixed feelings on opamp rolling and all that in general, but have the tools to properly measure it .


----------



## bnae38

After staring at this pic a few times, they're actually very well laid out amps. Lots of stuff in a tight space.. but good separation of the pre's. Amazing how small the power pcb is in the corner. Wonder what that header is.. 

Would be fun to play with on the bench.. and honestly despite my reluctance, would be a great amp to experiment with some upgrades


----------



## forty5cal1911

bnae38 said:


> After staring at this pic a few times, they're actually very well laid out amps. Lots of stuff in a tight space.. but good separation of the pre's. Amazing how small the power pcb is in the corner. Wonder what that header is..
> 
> Would be fun to play with on the bench.. and honestly despite my reluctance, would be a great amp to experiment with some upgrades


Yeah I was really quite impressed when I opened it up myself. That header is for the NVX logo led on the top plate.

You've got a PM. 

Big thanks to DeltaB and bnae38 and the others who have contributed to this thread!


----------



## wr3nchmonkey

So how soon until this happens?

I'm itching to hear the results


----------



## bnae38

Phil (forty5cal) has the parts in route to him, then sending the works to me.

I'll post up results within a few days after i receive, not one to procrastinate


----------



## dsquared

Sorry all , I think I missed it but what do the upgrades do?


----------



## bnae38

Potential for lower thd and noise, maybe better phase response. We shall see


----------



## bob01464

I am in the process of doing this upgrade myself. I will also be changing the 4 RC4558's to OPA2209's. Lower noise and distortion. Wider GBW, lower quiescent current. Had planned on using all Nichicon KZ Series Caps but found out that they are physically larger for the same rating and wouldn't fit in some locations so I ended up with a mix of KZ's and FG's. Both outstanding caps in my limited experience.


----------



## bob01464

Does anybody know of a source for the schematics for this amp? I work mostly vintage stuff and schematics are a lot easier to come by. Thanks guys


----------



## norurb

Ask nvx directly. I asked for their crossover schematic and they were happy to provide it.


----------



## bnae38

bob01464 said:


> I am in the process of doing this upgrade myself. I will also be changing the 4 RC4558's to OPA2209's. Lower noise and distortion. Wider GBW, lower quiescent current. Had planned on using all Nichicon KZ Series Caps but found out that they are physically larger for the same rating and wouldn't fit in some locations so I ended up with a mix of KZ's and FG's. Both outstanding caps in my limited experience.


I was under the impression they were all tl072 opamps stock?


----------



## DeltaB

bob01464 said:


> I am in the process of doing this upgrade myself. I will also be changing the 4 RC4558's to OPA2209's. Lower noise and distortion. Wider GBW, lower quiescent current. Had planned on using all Nichicon KZ Series Caps but found out that they are physically larger for the same rating and wouldn't fit in some locations so I ended up with a mix of KZ's and FG's. Both outstanding caps in my limited experience.


In the signal path, you can very safely use 35v or 25v, but I wouldn't use lower than 16v, unless the rail to rail voltage was 12v or less. In signal path caps, they are used for DC blocking, (which protects the rails from DC being introduced) you will very seldom ever experience anything that can send 50v, but engineers will sometimes opt for them. If you have a cheap cap that is 5mm diameter at 50v and you choose to use a Muse for example, and the 50v is 8mm for example, you can look to see if the same value (10uf for example) is at 35v 5mm and safely choose it. (12~15v on one side and -12~-15 on the other will come to less than 30v at worst case failure)

If you really want to make a significant improvement to the JRC4558, utilize the OPA1602. Same current, and much better sound than OPA2209, however it's SMD only.


----------



## forty5cal1911

DeltaB said:


> If you have a cheap cap that is 5mm diameter at 50v and you choose to use a Muse for example, and the 50v is 8mm for example, you can look to see if the same value (10uf for example) is at 35v 5mm and safely choose it. (12~15v on one side and -12~-15 on the other will come to less than 30v at worst case failure)


Is this why you used 35V Elna caps? I ordered 50V (8 mm) caps without verifying the physical footprint.

Also, I would be interested in what model Bob01464 is using as my JAD has the TL072's.


----------



## DeltaB

forty5cal1911 said:


> Is this why you used 35V Elna caps? I ordered 50V (8 mm) caps without verifying the physical footprint.
> 
> Also, I would be interested in what model Bob01464 is using as my JAD has the TL072's.


Yes, it is the reason for 35v. And the OPA1642 is drop in for TL072


----------



## bob01464

Thanks DeltaB I will look into OPA1602's. You have more experience then I do. Yea I figured I could probably drop the voltage a bit but the Nichicon Fine Gold FG's are very close to the same foot print. The KZ's were almost double in size. Should have checked dimensions before ordering. No biggie it was just another order to Mouser...LOL.

It is a 900.5 and all 11 of the TL072's were replaced with OPA1642's but there were 4 more 5mm by 5mm 8 pin SMD chips. These are the JRC4558's


----------



## bob01464

Hey DeltaB whats your thoughts on the OPA1612 in place of the JRC4558. Current looks to be comparable. I haven't really looked into them but they have some good reviews.


----------



## bnae38

You guys need to be careful throwing stupid fast opamps in here and hoping for "better" sound.

My .02.


----------



## bob01464

Oh I am definitely guilty of getting wrapped up in these type of things. But some of this is based off of what has worked well for people in the past. Mod fever strikes the best of us...LOL


----------



## bnae38

bob01464 said:


> Oh I am definitely guilty of getting wrapped up in these type of things. But some of this is based off of what has worked well for people in the past. Mod fever strikes the best of us...LOL


Fair enough, same here .

Hard to not get carried away. The amp is only as quiet dynamic or distortion-free as the the rest of design though. We're just playing with the pre-amp.

When we start going with 40-80mhz bw opamps, we open other doors for problems. Mostly oscillation.. especially with the picky high-end uber amps.


Would end up needing to beef up bypass caps, make sure feedback compensation is appropriate etc etc.. at the end of it i don't see it being worthwhile.

I'm in agreement replacing the tl072's with opa1642's seems like a good idea, i'll probably do it on my ks's soon. But the ne5532's will likely remain. Despite running hot, which kinda makes me , they're solid tried and true performers.

Not sure why nvx used JRC4558 in a few spots on the 5ch?


----------



## bob01464

Bnae38 you make a great point. I'm sure I don't have the same experience that you and DeltaB have. Love the insight. Bad part is the JRC4558's are already removed and gone. Might have to do a little more research. Looks like the OPA2209 is only a 18Mhz bw.


----------



## bnae38

bob01464 said:


> Bnae38 you make a great point. I'm sure I don't have the same experience that you and DeltaB have. Love the insight. Bad part is the JRC4558's are already removed and gone. Might have to do a little more research. Looks like the OPA2209 is only a 18Mhz bw.


10-4, TI calls out the opa2209 as drop in for that one (which i'm sure you saw).

Shrug. I've had good luck with it. Also seen it used in some high end gear .


----------



## bob01464

Even better is I will have them in hand tomorrow.


----------



## DeltaB

bnae38 said:


> You guys need to be careful throwing stupid fast opamps in here and hoping for "better" sound.
> 
> My .02.


I've used the OPA1602 numerous times. It's very well behaved. When you get slew rates past 50 in a bi-polar design, then you really need to make sure you don't engage in oscillations past the audible range by applying enough feedback, but both OPA1642 (JFET) and OPA1602 (Bi-Polar) are both around the 20 range. The OPA1602 is internally compensated, and TI specifically designed these (the SoundPlus 1600 series) for use in high end audio applications. The OPA2209 is not even listed for high end audio usage in any of the recommended usage types, but motor controllers.

The NE5532 (another non internal compensated bi-polar design) has been used since the 70's in many devices, and the rational has been if it is used to record (used for decades in many consoles) then it should be great for reproduction. And for a single instrument, it's acceptable, but has been eclipsed by numerous newer designs. DAC companies like ESS don't even recommend the NE5532 but for the very lowest of performance and is barely acceptable. But when you start piano smashing, (highly complex audio signals) you really need slew rates in the upper teens to twenties range. In the zenith of analogue audio amps, the magic really started happening around those slew rate speeds. The real issue is the recovery time, and needs to be in the low microsecond range, not milliseconds. (which both the OPA1602 and OPA2209 do exhibit, but the OPA2209's slew rate is slow)


----------



## bob01464

Looking at the datasheet it also shows a band width of only 35Mhz for the OPA1602. Not getting into the 40-80 range that could potentially be a problem. Looks like a solid choice. Your point about the slew rate makes perfect sense. 

JRC4558: Slew Rate 1.7 V/us, Band Width 3Mhz, Current 3.0mA, Distortion .008%

OPA2209: Slew Rate 6.4 V/us, Band Width 18Mhz, Current 2.5mA, Distortion .000025%

OPA1602: Slew Rate 20 V/us, Band Width 35Mhz, Current 2.6mA, Distortion .00003%

Really illustrates how weak the JRC4558 is
Love this stuff. Is there any other major factors that should be taken into consideration?


----------



## bob01464

I throw this out there only for comparison purpose

TL072: Slew Rate 13 V/us, Band Width 3MHz, Current 2.0mA, Distortion .003%

OPA1642: Slew Rate 20 V/us, Band Width 11MHz, Current 1.8mA, Distortion .00005%


----------



## JH1973

This thread is WAY over my head but nevertheless very interesting.I look very forward to Bnae's results.Please report back with unbiased and honest data.


----------



## bob01464

Unfortunately I have no base line to compare against. Bought new and tore apart. Yea there is something wrong with me...LOL. So it will be either a "Man this sounds great" (Probably Slightly Biased) or "I'm a dumb ass and don't do what I have done". I also would love to here from anybody doing a A to B comparison. I'm probably more doing this as I enjoy the challenge and always learn something along the way. Oh and of course have a addiction to good quality sound as I think most here do.


----------



## DeltaB

bob01464 said:


> Looking at the datasheet it also shows a band width of only 35Mhz for the OPA1602. Not getting into the 40-80 range that could potentially be a problem. Looks like a solid choice. Your point about the slew rate makes perfect sense.
> 
> JRC4558: Slew Rate 1.7 V/us, Band Width 3Mhz, Current 3.0mA, Distortion .008%
> 
> OPA2209: Slew Rate 6.4 V/us, Band Width 18Mhz, Current 2.5mA, Distortion .000025%
> 
> OPA1602: Slew Rate 20 V/us, Band Width 35Mhz, Current 2.6mA, Distortion .00003%
> 
> Really illustrates how weak the JRC4558 is
> Love this stuff. Is there any other major factors that should be taken into consideration?


With today's HU's and HD content, when you engineer a system, from that point of the DAC to the finals, any device between that DAC and finals has to exhibit some basic considerations. It has to exhibit less noise, faster performance, and as much rejection from common mode and power supply as possible, exceeding the dynamic range of the DAC. Since 16bit @ 44kHz requires speeds up the low 20µs range, and 24bit will be low 10µs range to cover to the LSB. (least significant bit) At 192kHz it will require into the nanosecond range. (and where you would want an op-amp like the OPA1612 with 500ns recovery) This is why you need low microsecond recovery time, and slew rates close to the swing of the rail to rail voltages/µs at the LSB to have the headroom to fully leverage what is actually coming out the DAC. Same holds true for any ADC circuit. It is why current modern design op-amps are required to really get the SQ you are looking for.


----------



## wr3nchmonkey

JH1973 said:


> This thread is WAY over my head but nevertheless very interesting.I look very forward to Bnae's results.Please report back with unbiased and honest data.


Same here. This is more technical information that I am experienced with at this point lol. I'm very excited to see what the results will look like. Very interesting thread.


----------



## bob01464

Ah I see what your talking about. The Overload Recovery Time. The OPA1602 doesn't look to bad at 1µs. I couldn't find any Time specs on the JRC4558

LOL...And I learned something new. How to type the µ symbol.


----------



## bob01464

Got shot down on the schematic request. Oh well it was worth a try.


----------



## bnae38

JH1973 said:


> This thread is WAY over my head but nevertheless very interesting.I look very forward to Bnae's results.Please report back with unbiased and honest data.


Yepper, that's all you're going to get from me. Just the data... 

Frequency response, phase over freq, thdn vs power output, etc. Before and after.

Havent decided what all i'm going to do beyond that. The Dscope uses ne5532 parts... so doesn't make a whole lot of sense for me to try to rig up slew testing.

Cmrr would be easy enough to check. Thdn over frequency at a few levels is nice for a sanity check..


----------



## vwguy383

Can you guys do a step by step build log when doing the mods please? Also, is the output going to increase? Or is the sound going to be better (in theory)? Would an amp dyno help with the results? If so, maybe bigdwiz could help. Maybe he could get a stock amp and modified one to test them.

Way over my head here too!

Thanks
Justin


----------



## bnae38

We are only modifying the preamps. Likely lower distortion and noise, better dynamic response, that kind of thing. Power output wont change. I'll try to get some pics as i mod.


----------



## bob01464

bnae38 I look forward to your results. Hopefully its worthwhile. Fun none the less.


----------



## JH1973

Hey Fcarpio,see what you started here!! Now everybody on the freakin' forum will begin to envision ripping their amps apart with dreams of better opamps,sexier resistors and stellar caps.Then they'll be going to Home Depot dropping some bread on a soldering gun with visions of clearer voices,a concert like soundstage that is ready to shatter the windshield by the sheer crispness of the highs! Gary Summers asking for their autograph after they blow the field away at the Meca world finals.........then they get home and begin to dissamble the amplifier and the fear starts to set in,heartrate starts to go up and the forehead beads up with sweat as they realize...."I don't know what the he#$ I'm doing,I've never soldered a dam thing in my life!"


----------



## DeltaB

JH1973 said:


> Hey Fcarpio,see what you started here!! Now everybody on the freakin' forum will begin to envision ripping their amps apart with dreams of better opamps,sexier resistors and stellar caps.Then they'll be going to Home Depot dropping some bread on a soldering gun with visions of clearer voices,a concert like soundstage that is ready to shatter the windshield by the sheer crispness of the highs! Gary Summers asking for their autograph after they blow the field away at the Meca world finals.........then they get home and begin to dissamble the amplifier and the fear starts to set in,heartrate starts to go up and the forehead beads up with sweat as they realize...."I don't know what the he#$ I'm doing,I've never soldered a dam thing in my life!"


In all honesty, Fcarpio didn't really start anything but to give a report on his compared to a few other amps. I must concede, that I am the one who brought this issue to the thread. And as I said early on, I am aware that not everyone has the skillset or the equipment to be doing these types of upgrades. However, it doesn't preclude the improvements to be found by addressing some very basic engineering shortcomings in the industry, where low cost/profit margins leaves the consumer with 30 year old, poor performing components. You don't have to look far to find out why when comparing various amps that they all sound the same, and more times than not, not so good.

If anything, what I hope we could do as a community, is to bring pressure to the industry. It would not, in the overall cost of the bill of materials, be prohibitive to utilize better components, but when and if they do they want 10x the cost of the product, if you can find them doing it at all.

But when you hear the difference between one that has been done, it takes less than 30 seconds to anyone who is half-deaf to point and say, "I want that one!"


----------



## EricP72

I think I might be back in on this. I'm torn between a pair of these vs a pair of Sony xm-gs4


----------



## DeltaB

manish said:


> I think I might be back in on this. I'm torn between a pair of these vs a pair of Sony xm-gs4


The Sony suffers the very same issue. It utilizes NJM4565's. However, if you did choose the Sony, I would use an OPA1602 bi-polar.


----------



## JH1973

Delta,you'll be receiving my amps in the mail for complete overhaul and you'll be paid handsomely for the work.


----------



## DeltaB

JH1973 said:


> Delta,you'll be receiving my amps in the mail for complete overhaul and you'll be paid handsomely for the work.


Thank you for the offer, however, there are shops out there that are equipped with the tools and the knowledge and available for these types of services, even listed in this thread and quite affordable. If I make a mistake and damage my equipment, then I have myself to blame. If I damage someone else's equipment, that is a liability that I am neither insured or bonded to do, and quite honestly would make me feel horrible.


----------



## JH1973

DeltaB said:


> JH1973 said:
> 
> 
> 
> Delta,you'll be receiving my amps in the mail for complete overhaul and you'll be paid handsomely for the work.
> 
> 
> 
> Thank you for the offer, however, there are shops out there that are equipped with the tools and the knowledge and available for these types of services, even listed in this thread and quite affordable. If I make a mistake and damage my equipment, then I have myself to blame. If I damage someone else's equipment, that is a liability that I am neither insured or bonded to do, and quite honestly would make me feel horrible.
Click to expand...

So I know much of this discussion is formed around the NVX amplifier.How can those of us who own different brand amps be able to tell if ours could benefit from an overhaul? I personally have a JL XD500 and a Fosgate PunchP400.


----------



## DeltaB

JH1973 said:


> So I know much of this discussion is formed around the NVX amplifier.How can those of us who own different brand amps be able to tell if ours could benefit from an overhaul? I personally have a JL XD500 and a Fosgate PunchP400.


There is no doubt that virtually any car audio amp can, with the current options we now have, find some significant SQ improvements. And this is something we as a community of end-users can try to help each other with possible recommendations.


----------



## bob01464

JH1973 said:


> Hey Fcarpio,see what you started here!! Now everybody on the freakin' forum will begin to envision ripping their amps apart with dreams of better opamps,sexier resistors and stellar caps.Then they'll be going to Home Depot dropping some bread on a soldering gun with visions of clearer voices,a concert like soundstage that is ready to shatter the windshield by the sheer crispness of the highs! Gary Summers asking for their autograph after they blow the field away at the Meca world finals.........then they get home and begin to dissamble the amplifier and the fear starts to set in,heartrate starts to go up and the forehead beads up with sweat as they realize...."I don't know what the he#$ I'm doing,I've never soldered a dam thing in my life!"


Hey I never thought about the sexy resistors...LOL. I personally think this is a great discussion and at the end we will have quantified results and a complete parts list with suppliers. At that point if someone whats to press ahead with this mod it really comes down to if they have the experience and tools or it can easily be outsourced. 

I do think it worth restating that this amp has received very good reviews as-is and can hold it's own with any other amp in its price range. So this is by no means a turd that were trying to obtain the new pro glow from. 

I do believe that the changes will give a satisfactory result and we are lucky that those results can be verified (Big Thanks bnae). Believe me you don't want me telling you it now has a oak flavored mid with a subtle hint of Jasmin up high...LOL. We could also find out the risk is not worth the reward either way I see it as a win.

And any time I can play mad scientist you can count me in. :z:


----------



## DeltaB

JH1973 said:


> So I know much of this discussion is formed around the NVX amplifier.How can those of us who own different brand amps be able to tell if ours could benefit from an overhaul? I personally have a JL XD500 and a Fosgate PunchP400.


The JL amp utilizes the JRC2068, (bi-polar) which a mid-level desktop radio quality buffer, and would see some improvements. The Punch uses the TL072 (JFET) and would certainly see a loss of hiss, much better phase control, and a much better high frequency response. For the JRC2068, I would use an OPA1602, (bi-polar) and the Punch the OPA1642 (JFET)


----------



## DeltaB

bob01464 said:


> Hey I never thought about the sexy resistors...LOL. I personally think this is a great discussion and at the end we will have quantified results and a complete parts list with suppliers. At that point if someone whats to press ahead with this mod it really comes down to if they have the experience and tools or it can easily be outsourced.
> 
> I do think it worth restating that this amp has received very good reviews as-is and can hold it's own with any other amp in its price range. So this is by no means a turd that were trying to obtain the new pro glow from.
> 
> I do believe that the changes will give a satisfactory result and we are lucky that those results can be verified (Big Thanks bnae). Believe me you don't want me telling you it now has a oak flavored mid with a subtle hint of Jasmin up high...LOL. We could also find out the risk is not worth the reward either way I see it as a win.
> 
> And any time I can play mad scientist you can count me in. :z:


While I appreciate the posting, an op-amp that is $0.20 each will not sound like a high quality op-amp that is $3.00 each. Just sayin'


----------



## bob01464

I totally agree with you DeltaB. I actually expect some really good things to come out of these mods. By the way I did opt for the OPA1602 as replacements for the JRC4558. Should have them tomorrow.


----------



## JH1973

bob01464 said:


> I totally agree with you DeltaB. I actually expect some really good things to come out of these mods. By the way I did opt for the OPA1602 as replacements for the JRC4558. Should have them tomorrow.


Are these mods difficult to do?How long does a typical amplifier take?


----------



## bob01464

Hardest part is waiting for parts to arrive...LOL. Truthfully its not that bad if you can replace the 8 pin SMD Op-Amps. That probably comes down to experience and practice. Plenty of tutorials out there. Oh and Removing those damn heat sink clips. Again there are You Tube videos on that. Besides that its probably a solid evening. Involves Replacing 11 TL072 Op-Amps (I also replaced the 4 JSC4558 Op-Amps) and probably close to 50 Caps (That might be a little high - I don't have it in front of me at the moment). I'll be glad to put up a parts list (Maybe Tomorrow) and we can edit it as needed. I can also toss up some pics latter as I should be working on it this evening.


----------



## DeltaB

bob01464 said:


> Hardest part is waiting for parts to arrive...LOL. Truthfully its not that bad if you can replace the 8 pin SMC Op-Amps. That probably comes down to experience and practice. Plenty of tutorials out there. Oh and Removing those damn heat sink clips. Again there are You Tube videos on that. Besides that its probably a solid evening. Involves Replacing 11 TL072 Op-Amps (I also replaced the 4 JSC4558 Op-Amps) and probably close to 50 Caps (That might be a little high - I don't have it in front of me at the moment). I'll be glad to put up a parts list (Maybe Tomorrow) and we can edit it as needed. I can also toss up some pics latter as I should be working on it this evening.


Easiest way to remove clips is use a allen wrench, size it to just fit hole, short end in the hole, long side pointing up. Gently use it like you would a crowbar and easy-pop off. Super easy. To replace, simply position and push towards the heatsing with your thumb and pop, it in goes.


----------



## bob01464

Aww you gave away the secret. Should have seen me struggling with my first one till I found out about that trick...LOL


----------



## DeltaB

bob01464 said:


> Aww you gave away the secret. Should have seen me struggling with my first one till I found out about that trick...LOL


Sorry I stole the thunder.. The backstage tattelings of insider tricks... :beerchug:


----------



## bnae38

All this bashing of the opa2209 (deltaB) made me wonder.. why did they use the 2209 in the pre's of our flagship mixers instead of the opa1602. 

Knowing the bossman, first thing i checked was noise. Voltage noise is close, 2.5 vs 2.2 nv/Rt.hz. But current noise isn't even close.. 1.8pA vs 500fA..

At the end of the day, the 1602 is actually cheaper so suite yourself. But look at all the information 


Much of this stuff is a trade-off when playing around. But anyway..


Keep in mind, just because TI didn't label the opamp "sound plus" doesnt mean it's not able to excel in audio use!


Regarding slew.. i need to find the article, but iirc anything above 6v/us is moot based on how music is recorded. Even with uhd source material.. I think it was nwavguy that wrote it.


Fwiw the company is listed in my profile and the mixers are black. I'm not posting that here. ..even though anyone who owned one could pop the top and see the opamps lol.. i'd rather not go there.


----------



## DeltaB

bnae38 said:


> All this bashing of the opa2209 (deltaB) made me wonder.. why did they use the 2209 in the pre's of our flagship mixers instead of the opa1602.
> 
> Knowing the bossman, first thing i checked was noise. Voltage noise is close, 2.5 vs 2.2 nv/Rt.hz. But current noise isn't even close.. 1.8pA vs 500fA..
> 
> At the end of the day, the 1602 is actually cheaper so suite yourself. But look at all the information
> 
> 
> Much of this stuff is a trade-off when playing around. But anyway..
> 
> 
> Keep in mind, just because TI didn't label the opamp "sound plus" doesnt mean it's not able to excel in audio use!
> 
> 
> Regarding slew.. i need to find the article, but iirc anything above 6v/us is moot based on how music is recorded. Even with uhd source material.. I think it was nwavguy that wrote it.
> 
> 
> Fwiw the company is listed in my profile and the mixers are black. I'm not posting that here. ..even though anyone who owned one could pop the top and see the opamps lol.. i'd rather not go there.


Take an op-amp, any op-amp of 6v/µs and place it's gain at 0db on +-15v rails, and play complex content from the DAC and record the waveform. (Take a CD like Margaret Becker's "Falling Forward" for example) Do that multiple times and superimpose the waves, and you will find that none of them will output the same. Then take that same complex content, and run it through an op-amp at 20v/µs at 0db and then superimpose. The result will be axiomatic.

There is a reason DAC companies like ESS do not recommend slow slew rate op-amps, in fact the NE5532 (9v/µs) isn't recommended on any of the 32bit DAC's and only the last choice for the ES9006, which is the lowest performing 24bit DAC in their lineup. Recording a single channel content and audio reproduction is two distinct things. Be careful what you read.


----------



## bnae38

Here's the article
NwAvGuy: Op Amps: Myths & Facts

Don't really wanna be the guy that rains on the parade, but i think these things should be taken with a grain of salt.

Can we get better noise floor, thd, and phase response? Yes. Is that worth it, hell i think so..

Will the difference be mind boggling? I don't know about that..

Getting that last 5% when you're 95% of the way there isn't easy. No question this could be part of it. Just go into it being realistic.

Fwiw


----------



## bnae38

DeltaB said:


> Take an op-amp, any op-amp of 6v/µs and place it's gain at 0db on +-15v rails, and play complex content from the DAC and record the waveform. (Take a CD like Margaret Becker's "Falling Forward" for example) Do that multiple times and superimpose the waves, and you will find that none of them will output the same. Then take that same complex content, and run it through an op-amp at 20v/µs at 0db and then superimpose. The result will be axiomatic.
> 
> There is a reason DAC companies like ESS do not recommend slow slew rate op-amps, in fact the NE5532 (9v/µs) isn't recommended on any of the 32bit DAC's and only the last choice for the ES9006, which is the lowest performing 24bit DAC in their lineup. Be careful what you read.


Well, i did read the noise specs. 

All for the sake of discussion, and two sides to every coin...

The slew difference for complex material (ie we dont listen to sine waves..) makes sense. True enough.

I'm not smart enough to punch out the math, but anyway...


As i've geared up my lab, this was always the endgame... to play around with better components/changes/etc (as well as the repairs i do).


I haven't started yet, but will be playing with my ks900.6 soon. Point being, i dont know how big or small the difference will sound... i'm just programmed to be skeptical first


----------



## bob01464

Glad to see both the TL072 and 4558 were both on NwAvGuy's Don't Bother list. At least makes me feel like we are addressing weaknesses.

Quote from NwAvGuy article:

DON’T BOTHER: While the following parts had their glory days, they’re long gone. They offer no advantage over the above parts and are often much worse:

*TL071/TL072 – These were mainstream audio parts and used in lots of pro gear before the 5532 came along. For all those speed freaks, it’s worth noting they’re rated only slightly slower than the elite chips at 15 V/uS. They were also among the first reasonably priced FET op amps that were useful for high quality audio. But they suffer from very limited output current, they can’t get very close to the rails, have higher distortion, and they’re relatively noisy. Their lower power cousins the TL061/TL062, and the lower spec TL081/TL082 are even worse.
LM833 – This was one a National’s early attempts at a high performance audio op amp like the 5532 but they failed to beat the 5532.
4560 – The 4560 has been eclipsed by the NJM2068, 5532, 4556, etc.
4558 – Same as above


----------



## forty5cal1911

bnae38 said:


> Here's the article
> NwAvGuy: Op Amps: Myths & Facts
> 
> Don't really wanna be the guy that rains on the parade, but i think these things should be taken with a grain of salt.
> 
> Can we get better noise floor, thd, and phase response? Yes. Is that worth it, hell i think so..
> 
> Will the difference be mind boggling? I don't know about that..
> 
> Getting that last 5% when you're 95% of the way there isn't easy. No question this could be part of it. Just go into it being realistic.
> 
> Fwiw


Yeah that's the Engineer's blog that put me over the edge on the whole thing. I am definitely interested to see the hard data. I think we should start a separate thread for the purpose of posted measured data of their op-amp replacements and for further discussion.

Parts came in today Ben and amps are being sent out tomorrow.

Bob, I certainly agree that we should be addressing a common weakness and should net some gains here.... at least that is my hope. There are several other blogs and forums with corroborating data on the TL07x's. It's about the lowest cost, bottom of the barrel op-amp for use in audio from what I can tell.


----------



## DeltaB

bnae38 said:


> All this bashing of the opa2209 (deltaB) made me wonder.. why did they use the 2209 in the pre's of our flagship mixers instead of the opa1602.
> 
> Knowing the bossman, first thing i checked was noise. Voltage noise is close, 2.5 vs 2.2 nv/Rt.hz. But current noise isn't even close.. 1.8pA vs 500fA..
> 
> At the end of the day, the 1602 is actually cheaper so suite yourself. But look at all the information
> 
> 
> Much of this stuff is a trade-off when playing around. But anyway..
> 
> 
> Keep in mind, just because TI didn't label the opamp "sound plus" doesnt mean it's not able to excel in audio use!
> 
> 
> Regarding slew.. i need to find the article, but iirc anything above 6v/us is moot based on how music is recorded. Even with uhd source material.. I think it was nwavguy that wrote it.
> 
> 
> Fwiw the company is listed in my profile and the mixers are black. I'm not posting that here. ..even though anyone who owned one could pop the top and see the opamps lol.. i'd rather not go there.


Please note rating for voltage noise between the 2209 (rated between 0.1hz to 10hz) and 1602 (rated between 20hz to 20khz) TI currently suggests the 2209 as a replacement for the old NE5532, and is much quieter. Amp input buffer devices are not being used for I/V conversion and are current isolated and configured as single-ended voltage buffers, not current buffers. I can assure you, Texas Instruments knows their own product, and what it's intended purposes should be. And while I appreciate some of what Northwest had to say, please note that his article was done in 2011, and contains none of the more recent choices we have available to us. If you find anything JRC in your device, you're actually working from the same process design carried over from the original JRC 4558 die process. And while they may sound great in lower end/cheap cost tabletop radio applications, (there is a reason they are $0.20 each) they are certainly overshadowed by the current laser die processes used at TI for some of their latest offerings. Will those older op-amps make sound? Yup. Will it be accurate time and again in reproduction? Will it present the kind of soundstage that can be heard with some of the offerings I'm suggesting? Not no, but heavens no.


----------



## DeltaB

I was asked the question about the reference of what is "piano smashing?" In the late 60's on some college campus' was a contest where a 4" pipe in a wall was used to pass an entire grand piano, smashing the piano into smithereens and shoved through the 4" pipe, and the first group to accomplish it would win. In recording studio's when you take 32 or 64 or however many individual tracks that have been recorded and then pass it into a stereo signal with the entirety of those various tracks, would be analogized as "piano smashing"... :smash:


----------



## bob01464

Hell that just sounds like fun...LOL


----------



## JCsAudio

After reading that article, I’m not convinced that switching the op amp is going to make a difference and if you think it does than one could cite “SIGHTED LISTENING” from that article as influencing your perceived listening experience. Someone would have to do a blind test with the original amplifier and the modified one with gains and everything being exactly equal to make an attempt at a valid unbiased listening test that is believable. I’ve read articles written for home audio equipment where $400 amplifiers were compared to $5000 amplifiers in blind testing that were used within their design limits and the results showed that no one could consistently guess which one was better. 

I personally own 10 different auto amplifiers from higher to lower quality such as NVX, and I have 7 running now in three different vehicles. I have owned many others I sold and other than differences in power output could not say any of them sounded diffferent in any way where they colored the sound attributable to the amplifier. I even swapped a higher quality 4 channel for a lower qaulity 4 channel of equal power and couldn’t tell a difference as far as the sound was concerned.


----------



## forty5cal1911

V8toilet said:


> After reading that article, I’m not convinced that switching the op amp is going to make a difference and if you think it does than one could cite “SIGHTED LISTENING” from that article as influencing your perceived listening experience. Someone would have to do a blind test with the original amplifier and the modified one with gains and everything being exactly equal to make an attempt at a valid unbiased listening test that is believable. I’ve read articles written for home audio equipment where $400 amplifiers were compared to $5000 amplifiers in blind testing that we’re used within their design limits and the results showed that no one could consistently guess which one was better.
> 
> I personally own 10 different auto amplifiers from higher to lower quality such as NVX and have 7 running now in three different vehicles and have owned many others I sold and other than differences in power output could not say any of them sounded diffferent in any way where they colored the sound attributable to the amplifier. I even swapped a higher quality 4 channel for a lower qaulity 4 channel of equal power and couldn’t tell a difference as far as the sound was concerned.


The idea here is to perform a benchmark measurement between the lower quality op-amps and the modern op-amps. Technical spec wise the modern should perform better.... meaning much cleaner, without the technical limitations of legacy technology.

I absolutely agree that there is a listening bias with sighted listening. How much of the improvement will actually show up in what we hear can be debated. I think the only objective measurement via listening that I will be willing to give is something along the lines of detectable hiss has disappeared at amplitude levels it could previously be detected.

Some of the headphone, computer audio and home audio forums are absolutely filled with nonsense and faulty evaluation with people performing various op-amp "rolling" and claiming that such and such provided such a wide soundstage vs such and such having a much narrower etc. etc. These threads are usually filled with non-quantifiable descriptors and IMO are highly biased. For example rolling op-amps on high quality sound cards is all the rage in computer audio it seems. The sound cards being modified were engineered by actual Engineers not home hobbyists and contained modern high quality op-amps optimized for the circuitry to begin with. If there was any objective change in sound it was because the op-amp was not operating properly in the circuit they installed it in.

All I am asking for from a high quality op-amp is no discernible noise resulting in pure transparency. Improved phase rotation across the audible spectrum would be a nice addition to boot.


----------



## bnae38

Mod info here http://www.diymobileaudio.com/forum.../373890-nvx-jad800-4-modification-thread.html

Had to order some different parts, results this week (i hope).


----------



## hackn3y

Anyone know if there are any reports of the NVX JAD900.5 making speaker noise with only a battery connected. There is a thread regarding this issue with the Polk Audio D5000.5 and PPI 5 channel, and all these have very similar designs. I have the polk amp, and it makes the static/hiss sound. It also has noise coming through the speakers when the gain is barely turned up and gets louder as the gain is increased, again with only a battery connected. All the noise issues go away once music is played and turned up past a certain volume. I was hoping to fix my amp, and I didn't know if this mod might have any effect or if anyone knew of any further knowledge regarding repairing this issue? I guess there are many amps using this design, but I haven't had any luck finding any fixes. I was about to just deal with it until my PPI DSP-88R stopped working, so I might just replace them both, but I didn't want to run into the same issues.


----------



## rton20s

Are your noise, popping, hissing issues present both with and without the DSP-88R? Your best bet is probably testing/replacing one component at a time. Especially when one of those components is as notorious as the DSP-88R.


----------



## hackn3y

rton20s said:


> Are your noise, popping, hissing issues present both with and without the DSP-88R? Your best bet is probably testing/replacing one component at a time. Especially when one of those components is as notorious as the DSP-88R.


Yes, the amp is out of the car and I have it only hooked up to a battery with 12V, GND, and the remote jumped to 12V and the hissing plays through a speaker. It is the same in both front channels and goes away when I increase the gain. The rear channels act differently. The DSP-88R was a separate issue, but it basically just semi died, and I haven't found any information for fixing it.


----------



## rton20s

hackn3y said:


> The DSP-88R was a separate issue, but it basically just semi died, and I haven't found any information for fixing it.


Same fix as the Audison Bit processors.


----------



## number41

Can anyone confirm the length of the JAD900.5? On their website it says 14.75", on Sonic Electronix it says 12 8/10 (which is 12 4/5???). That's not alot different but I'm trying to see if this will go under the seat of a Jeep wrangler.


----------



## wr3nchmonkey

I'm not sure the size of the 900.5 but I have the 800.4 and it will DEFINITELY fit under the seat. Tiny little amp with plenty of power.


----------



## number41

wr3nchmonkey said:


> I'm not sure the size of the 900.5 but I have the 800.4 and it will DEFINITELY fit under the seat. Tiny little amp with plenty of power.


Yeah, I was considering that amp but now thinking of a 5 channel.


----------



## Gibberish

NVX amps always have interested me. Does anybody know if they still make the 1200.1? They seem to have been out of stock for a minute now.


----------



## wr3nchmonkey

Gibberish said:


> NVX amps always have interested me. Does anybody know if they still make the 1200.1? They seem to have been out of stock for a minute now.


Hmm they are STILL out of stock on sonic...strange
Slow boat from china maybe

Sent from my SM-G965U using Tapatalk


----------



## JH1973

Can somebody tell me if this amp is bridgeable.I want to run 2 front speakers and a sub.Front speakers are 4ohm so could I bridge the main channels? I couldn't find enough info on it.Thanks....

Edit.....Nevermind,I found out that yes it can be bridged.


----------



## Aslmx

I’m pretty sure you can bridge it. I have one I’ve had for over a year still in the box. I’m going to bridge it to run some 6.5s. I was going to use it until I found a Kenwood excelon 900-5. The Kenwood has a lot stronger sub channel.


----------



## gw2405

Upgraded to an arc 1100.5 and gave my 900.5 to my brother.

We installed it in his car today and could not, for the life of me, figure out how to bridge it.

Used this image in the manual, set the switch to "bridge" and would only get audio out of the left side. Switching it to "2ch" gave us audio out of both sides, but both the front and rear gains were active, corresponding to left and right side..and without any rcas plugged into the rear input

What gives? 
Is the manual wiring method for bridging wrong? Am I overlooking something?










Sent from my ONEPLUS A6013 using Tapatalk


----------



## MrHarv

I believe that the 2 channel mode allows you to use one set of rca’s for front and rear channels instead of having to install 2 sets. You lose the ability to fade front to back. 


Sent from my iPhone using Tapatalk


----------



## gw2405

Ahh thanks! Explains that
Still doesn't explain why when using the supplied diagram for bridge, it's not bridging and I only get sound out of the left door

Sent from my ONEPLUS A6013 using Tapatalk


----------



## imickey503

This has been one heck of a great thread. I have upgraded some stuff over the years, but this wave of working with old skoool amps and doing the upgrades really has me thinking. 

I have an Old Clarion that has stopped working. And I want to get it back up to snuff and working again. Along with doing some upgrades. I can do the Caps as that is easy. But I want to see just what is possible, and maybe try to live stream it showing how I do all the mistakes.  

I actually bought a SOldering station with heat gun for this reason. My next Purchase is just a Inexpensive PC based Scope. 

Again thank you everyone in this thread!


----------

