# Modify amplifier sound quality, locating the decoupling capacitors



## diegoejea

Hi all,

I have a Rockford Fosgate T1000-4 amplifier. 

I want to change the decoupling capacitors (not sure if you call them like this in english...) from the preamplifier section, which use to be in series with the audio input, and they are used to remove the DC component from the audio input. 

Sometimes you can find 2 or 3 along the preamplifier section, in series, so the audio pass through them. 

It is a good improvement to upgrade them, in Home Hifi and car audio amplifiers. 

I want to locate them in my amplifier, but Rockford don´t make public the schematics until 2 years later the amplifier´s production has finished.

Any tip to locate these capacitors in my amp?? How to know the capacity values?

Any way to get the schematics?

Any advice about what capacitors to use instead of the SMD included in the amp??

Thanks to all


----------



## diegoejea

Sorry for my english, when I say decoupling capacitors, I wanted to say COUPLING CAPACITORS: the ones which are inline with the low level audio signal, and rejetc the low frequency and DC component.

Any help?


----------



## Mike_Dee

Why don't you post up some quality close up pics, so we can try to help?


----------



## diegoejea

Thanks Mike,

I will try to do it, but I won´t be able in some weeks...

for the moment, I post the RF web picture, 










As you can see, just at the RCAs inputs, can be seen some small capacitors. It seems they are 2 per input. 

I have the schematics for an old RF amplifier (attached). In it, you can see there are 2 couplig 0.1 uF capacitors just at the input. 

Do you think my T1000 can have be designed in a similar way?

Apart from this 2 couplig capacitors, you can see in this schematics (not my amplifier´s, remember, but just comparing to guess) that there are more capacitors along the audio way. I suppose they belong to the Eq section, Filters, etc. But you can´t bypass them by switches in my amp.

So, do you think I would exprience a sound improvement if I just replaced the first 2 couplig capacitors??

I would like to bypass the Eq section, but I could´t get the schematics for the T1000-4. People from rockford told me they can´t distribute the schematics unless have past 2 years from the end of the production of the amplifier. And they said it is still on production...

I


----------



## diegoejea

My intention for the next future, is to replace these 2 coupling capacitors per line, for a Mundorf, Elna Silmic, Panasonic, etc capacitors...

Which ones would you reccomend? Any different brand suggestion?


----------



## Moon Track

It’s a meticulous but possible work. 
The brand has nothing to do here.
You need in capacitors with low dielectric absorption(loss factor), there are no ceramic capacitors with low loss factor except COG or so called NPO , all of them have too low capacitance to be usable as a coupling capacitor. 
The ceramic capacitor with polar dielectric has a small dimensions but also it has a high loss factor, usually 0.02-0.08.
As an approximate reference , there are
polyester capacitors (absorbtion factor 0.005-0.01)
polypropylene sulfide film capacitors (0.001-0.007), 
polypropylene capacitors	(0.0002-0.0005).
There are Polycarbonate , Polystyrene and other exotic materials , but all of them have bigger sizes than ceramic capacitors.


----------



## envisionelec

Moon Track said:


> It’s a meticulous but possible work.
> The brand has nothing to do here.
> You need in capacitors with low dielectric absorption(loss factor), there are no ceramic capacitors with low loss factor except COG or so called NPO , all of them have too low capacitance to be usable as a coupling capacitor.
> The ceramic capacitor with polar dielectric has a small dimensions but also it has a high loss factor, usually 0.02-0.08.
> As an approximate reference , there are
> polyester capacitors (absorbtion factor 0.005-0.01)
> polypropylene sulfide film capacitors (0.001-0.007),
> polypropylene capacitors (0.0002-0.0005).
> There are Polycarbonate , Polystyrene and other exotic materials , but all of them have bigger sizes than ceramic capacitors.


DA isn't everything - and it's almost nothing in low impedance, audio frequency circuits.

I've been spec'ing Niobium Oxide capacitors for my high end customers that demand miniaturization of their products. It's an excellent alternative to aluminum.


----------



## Moon Track

In standard application ,the operational amplifier has 1-20kOhm input resistance. Often there are used a high resistance attenuating circuits without any compromise for signal quality. I don’t see a reason to speak about low impedance circuits. Signals there can be 10-30volts p-to-p and using a tantalum or niobium capacitors, with their leaks and tunneling effect,… I don’t see how it will improve the sound quality. If only you will use it for power filtering.
Capacitors with high loss factor contribute to third harmonic. For precise audio filters, the second most important parameter, is thermal stability.


----------



## diegoejea

PLEASE, DON´T GET CONFUSED (like I was at the begining of the post...). what I am asking in this thread is about changing the COUPLING CAPACITORS, the ones which are INLINE in the audio path, IN SERIES, and their function is to remove DC and low frequency components in the audio signal. 

All acapcitos have residual behaviours (ESR, ESL, memory effect, leakage, etc). Some types are better than others, of course. The point is, as they are in line with the audio signal, their residual behaviour affect the audio signal. 

In Home Hiend DIY, people use to improve these capacitors to get a cleaner audio path. 

This is what I want to do. But I don´t have the schematics of my T1000-4. 

The most often used capacitor for this pourpose are:

Elna Silmic II
Nichikon
Mundorf
Black Gates
...

They are very good capacitors, with minimized residual effects. Anyway, they exist...

These capacitors are famous for adding a special character to the sound. Of course, the best coupling capacitor would be the NO CAPACITOR. But if you are obligated to use them, the lesser the residual behaviour, the better the sound. 

By the way, the best fitted capacitors for this pourpose, use to be very large to use in comercial car audio amplifiers. This is teh reason amplifiers use to include small electrolitic capacitor for this matter.


----------



## Moon Track

All these manufacturers have different quality caps for different purposes.
ESR is just a derivative from loss factor. Inductance is not that parameter 
you want to look for low frequency signals ,but it doesn’t hurt to compare.
Most like, not much electrolytic capacitors are used in your amp as a coupling capacitor. Almost any ceramic capacitor works better, as a minimum the same as electrolytic cap, even if it is rated as an audio grade.


----------



## diegoejea

Moon Track said:


> All these manufacturers have different quality caps for different purposes.
> ESR is just a derivative from loss factor. Inductance is not that parameter
> you want to look for low frequency signals ,but it doesn’t hurt to compare.
> Most like, not much electrolytic capacitors are used in your amp as a coupling capacitor. Almost any ceramic capacitor works better, as a minimum the same as electrolytic cap, even if it is rated as an audio grade.


Yes, I think there are not much coupling capacitors in my preamplifier section. According to the schematics of the previous rockford model I attached above, there are just a few (3 or 4).

If I swap these ones, for others with much better parameters, the sound will be noticeabily improved. As you can see in the pictures, the first coupling capacitors, which are just at the RCAs input (2 per input), are small electrolitic ones. 

Comparing the pic with the schematics, maybe their capacity is 0.1 uF or 0.47 uF. For this capacity, an electrolitic cap is quite small. But a polypropilene one like Mundorf, with gold foil, is much larger for the same capacity. 

So, I want to get the compromise solution, finding the best capacitor I can use to substitute mines, but fit the space. I will take pics in some weeks.

A colleague of mine has changed his caps in a DLS A5 amplifier (he was lucky, he got the schematics directly from DLS, and his amplifier only had 2 caps per input line). He describe the change like "day and night", if you are a guy concerned about HiEnd results.

The caps he used are Mundorf with Gold Foil and oil, as far as i remember, very famous caps for this matter.

In this video, you can watch his upgrade. But you will see a lot of new caps also, because he changed the decoupling capacitors as well.


----------



## Moon Track

Polyester capacitors they are in two times smaller but also a bit worse.
They are somewhere between ceramic and polypropylene.
Metallized polypropylene sulfide also are quite compact.
Spectra plus program measures the THD you can try it to see what improvement you have, though much depends from your sound card. There was one month trial on their site.


----------



## diegoejea

Thanks Moon Track,

I would like to use well know caps, commonly used for this audio coupling improvement. 

For sure, the technologies you comment are able to fit my needs. But i would prefer not to test and try a lot of different components. I would like to restrict myself to the most used caps and best regarded for this puorpose. We have to trust in the experience of thousands of people who tested and listened to a lot of different caps before! 

I think we all agree that, although everythng in music is physics and measurable, most of times human being doesn´t know completely which parameter affect to some psicoacustic perception. So, better than choosing the caps in a blind way, just by some of their specifications, i would like to trust in the experience of gold ears who tested a lot before ;-)

Thanks for the help, everything is interesting

As


----------



## envisionelec

diegoejea said:


> PLEASE, DON´T GET CONFUSED (like I was at the begining of the post...). what I am asking in this thread is about changing the COUPLING CAPACITORS, the ones which are INLINE in the audio path, IN SERIES, and their function is to remove DC and low frequency components in the audio signal.
> 
> All acapcitos have residual behaviours (ESR, ESL, memory effect, leakage, etc). Some types are better than others, of course. The point is, as they are in line with the audio signal, their residual behaviour affect the audio signal.
> 
> In Home Hiend DIY, people use to improve these capacitors to get a cleaner audio path.
> 
> This is what I want to do. But I don´t have the schematics of my T1000-4.
> 
> The most often used capacitor for this pourpose are:
> 
> Elna Silmic II
> Nichikon
> Mundorf
> Black Gates
> ...
> 
> They are very good capacitors, with minimized residual effects. Anyway, they exist...
> 
> These capacitors are famous for adding a special character to the sound. Of course, the best coupling capacitor would be the NO CAPACITOR. But if you are obligated to use them, the lesser the residual behaviour, the better the sound.
> 
> By the way, the best fitted capacitors for this pourpose, use to be very large to use in comercial car audio amplifiers. This is teh reason amplifiers use to include small electrolitic capacitor for this matter.


I'm hardly confused. But unlike you speculators, I actually design high end audio equipment.



UNSUBSCRIBED.


----------



## BowDown

Ok, not trying to poke a caged animal here.. but why would someone start with a new Rockford amp and try to turn it into a SQ amp?


----------



## diegoejea

envisionelec said:


> I'm hardly confused. But unlike you speculators, I actually design high end audio equipment.
> 
> 
> 
> UNSUBSCRIBED.


I am afraid you misunderstood my intention, I am sorry, It is because my bad english. 

Sorry If I sounded rude or whatever impolite. Just I wanted to say that I prefer to try known caps, to spend time trying different random caps basing my selection in their theoretical parameters. I would prefer to narrow the list, go straight and spend less of my time in tests of different caps. Just that, not 
pretended to reject or look down your interesting help at all. I apologize for my bad english... 

Regards


----------



## diegoejea

BowDown said:


> Ok, not trying to poke a caged animal here.. but why would someone start with a new Rockford amp and try to turn it into a SQ amp?


Because is the only amp of several Hi End amps I have owned, which can excite with stamina and sound quality a pair of Dynaudio Esotar 650. 

this amp is really good at SQ, much more than believed...

YouTube - TheJirou111's Channel


----------



## Mike_Dee

This brand is widely used in the finest home audio amplifiers for decoupling use, and cant be purchased through Mouser Electronics - Electronic Component Distributor

WIMA - Competence in Capacitors


----------



## diegoejea

Mike_Dee said:


> This brand is widely used in the finest home audio amplifiers for decoupling use, and cant be purchased through Mouser Electronics - Electronic Component Distributor
> 
> WIMA - Competence in Capacitors


Thanks Mike,

I used Wima caps in the past to build some filters, and to improve others. Actually, they did an improvement in the filter over the electrolitics, regarding the top end airyness, clarity, and overall sound quality. 

But, I think Mundorf MCAP Supreme are even better for coupling. At least, people who are trying all these options, use to finally choose Mundorf, BlackGate, and some others. Of course, it depends on the application, but for coupling, these seem to be prefered. As far as I know.


----------



## Mike_Dee

This guy sells high end specialty caps, and the like. You'll need Adobe Reader since it's a .pdf file. I think Black Gate, and Nichicon "Muse".

http://www.percyaudio.com/Catalog.pdf


----------



## rexroadj

diegoejea said:


> Because is the only amp of several Hi End amps I have owned, which can excite with stamina and sound quality a pair of Dynaudio Esotar 650.
> 
> this amp is really good at SQ, much more than believed...
> 
> YouTube - TheJirou111's Channel


X2! I had my doubts about them till I actually fired one up....Very Impressive amps. Very robust as well like you said. When you need to move some mids there are not a ton that can do what these amps will. Keep us posted when you do the "mod" I am interested to see what the difference would be?
Its way out of my realm of knowledge.....any way to show any sort of "test" to "show" specific quality gain?


----------



## subwoofery

Would like to know the band and name of this song please. 

Thank you 
Kelvin


----------



## diegoejea

subwoofery said:


> Would like to know the band and name of this song please.
> 
> Thank you
> Kelvin


Hi Kelvin,

A friend of mine said this song is called: "Wind God and Thunder God: -Pia-no-jac- Typhoon". I did a quick search on youtube but i couldn´t find it by the moment.

Regarding the amplifier modification:

Finally, after several weeks investigating through HiFi forums, I changed the couplig capacitor for a better ones. 

The capacitors removed were the ones in the green circle (and the same for the others in the right):










They are 2 per channel, so I changed the 8 SMD capacitors you can see in the pic, for Metal Film Capacitors.

The new capacitors chosen were Mundorf Supreme, the ones who are better regarded by a lot of HiFi modders. Their behaviour is very ideal, they have very few residual behaviour, so they act as an almost transparent part in the signal path. Some of the people who used them, and compared a lot of capacitors for couplig, say that these ones behave almost as "no capacitor", what is ideal for this mod. 

Unfortunately, I forgot to take any picture of the result. But the capacitor fitted exactly along the area you can see in the pic. 

THE RESULT

Simply awesome, worth. The sound become cleaner. This amp sounds clean by default, though, but it makes it even cleaner. The highs now are more airy in the top end, and the overall sound seems more accurate and sharp. 

This is not a night and day change. But when you are used to the sound of this amplifier, it is very easy to notice the improvement. It is like removing a cloth from the front of the loudspeakers. The sound is cleaner and less colored at all frequencies. 

The T1000-4 is an incredible amplifier for sound quality, but with this mod, is even more impressive. 

Like some Japanese guys, I use this amp to feed 2 Dynaudio Esotar 650, and 2 Morel Supremo Piccolo, and this change is really worth for the money. It costed about 80 euros.


----------



## 808Munkyeee

wowwwwwwwwwwwwwwww


----------

