# Class D Amps and HLCD



## POLKAT

Has anyone had any issues using Class D amps with HLCD's?

First and foremost, when it comes to amps, I am firmly in the camp of Class D sounding just as good as class AB. 

That being said, I've seen a few people say that Class D amps can be "noisier" than their AB counterparts and, high-sensitivity HLCD's can make that noise stand out.

Is there any truth to this or is this just a case of some people being fundamentally against using Class D amps for anything other than subwoofers?

Thanks!


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## ca90ss

From my experience the lower cost class d amps do tend to have a bit more noise than a comparable a/b but the higher quality ones are as good as any a/b I've used. Whether a/b or d though the best thing if possible is to try the amp before buying. When I bought my amps I took a horn to the stereo shop and tried a bunch of amps and bought the quietest one.


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## POLKAT

Sounds like a great plan. I'll wait to buy any new amps until after I get my horns so I do the same thing.


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## Patrick Bateman

I generally found the opposite. Class D is inherently noisy, and due to that, Class D designs tend to be better designed to reject noise, in my experience.

In my projects, my MiniDSP are always the noisy parts.


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## POLKAT

I have been planning to use a Minidsp as well. Would it be prudent for me to go with another brand for HLCD or is the noise manageable via gain settings?


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## nadams5755

you could see how the minidsp goes w/ its 2v preouts, pick up a linedriver to mitigate the gains, or upgrade down the road to another dsp w/ higher preout voltage. you might not even need higher gain levels w/ the horns.

i have switching noise w/ the minidsp 2x4 at home when it's powered by my pc. i haven't tried it in the car yet.


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## thehatedguy

I have my whole system on my Soundigital GaN fet amps right now. I do have some gain hiss, but I think it is from my Helix DSP Pro.

The problem is that you are more than likely would be listening to the noise floor of the amp since your speakers are so sensitive and the SNR increases as output levels increase...and with horns you'll might be listening to a watt or two...maybe 3 wide open.


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## Hillbilly SQ

POLKAT said:


> I have been planning to use a Minidsp as well. Would it be prudent for me to go with another brand for HLCD or is the noise manageable via gain settings?


It depends on which Minidsp you get. My old 6x8 with 2v preouts is quiet as a church mouse. My 8x12 while way more powerful along with 6v preouts has hiss that gets worse with higher sensitivity drivers (noticed it fast when switching from my Seas neo aluminums to the more sensitive Audiofrog GB10's). That said, as Winslow stated the horns will only need a few watts to run you out of the car and will most likely have the gains bottomed on the horn amp with levels pulled down in the dsp. My 8x12 does seem to sound more "open" at least but no way I'd run it on horns.


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## ErinH

Two major factors:

The SNR of the amp at 1w. Most manufacturers don't provide this and the ones who do show a rating in the 80's. Instead they only provide the SNR at rated power (which typically is > 100dB). However, this spec is terribly useless when it comes to having high sensitivity drivers. You care about the SNR with little/no power applied which would be captured by a "SNR at 1w" type spec. 
The sensitivity of the drivers. If you have a compression driver with 110dB sensitivity then pretty much any noise is going to be amplified. If your drivers are in the mid-90's you may get some noise but it won't be as bad. And if you have a driver in the 80's then the SNR of the system (amps, headunit, dsp, whatever) will probably not be noticeable (unless the SNR is way below the sensitivity of the drivers).


I've run in to this issue with both my HT setup and in my recent car update. The amps I'm using for home are Crown XLS v2 and in the car I am using the JL Audio XVi amps. Both are perfectly acceptable for mid-sensitivity drivers (upper 80's to 90dB sensitivity). However, with my high sensitivity compression drivers (HT drivers are rated at >110dB and my new car drivers are 110dB) there's noise floor in both cases. I can't really fault the amps, per se, because I doubt the manfucaturers were designing them for these particular cases with uber-sensitive drivers. 

With my HT I just deal with it since I don't use it as a critical listening room. The sounds of the movies override the hiss, I'm far enough away that it's not really bothersome, and I just don't want to pony up the cash for a home amplifier for 3 channels (L/C/R). 

But for my car, I had to do something about it because it was unnerving. So a friend pointed me to and I ordered a Soundstream Reference 300 amp that had been modified by Gordon Taylor. The information Gordon provided said the amp's original SNR at 1w was 84dB which is pretty commonplace even today (15+ years later). Gordon modified the amp to be used specifically with compression drivers and tweaked it to be 100dB at 1w. That solved my noise floor issue entirely and now my system is completely noise free; even with my higher sensitivity midranges powered off the XVi amp. 

All that to say this:
I don't think the problem is inherent in Class D amps. Based on my research most amps have an SNR in the 80's at 1w; even some of the nicer Class AB amps. When it comes to compression drivers you don't care about the "SNR at rated power"; you'll never provide a 110dB sensitivity driver with 100 watts in your car so that spec is totally useless to you. You care about the SNR with little/no power applied which would be captured by a "SNR at 1w" type spec. So keep your eyes peeled for that. And good luck with getting that info. You'll probably have to email manufacturers to ask them what that spec is and IME you may not get a reply back at all. Which means, unfortunately, some dice rolling. Or finding a modified one like I did.


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## Babs

Yep I imagine S/N ratio is one of those specs that’s easily overlooked, at least by me. Something to keep in mind for sure. And as Erin has explained, high sensitivity drivers will certainly require us to consider that critical spec with amp selection, along with all over noise inducing items other than amps as well I can imagine. 


Sent from my iPhone using Tapatalk Pro


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## POLKAT

It's crazy that even a Reference 300 was noisy with compression drivers. Cs90ss' advice of trial and error with amps may be the best way for me to go, considering that specs can indeed be misleading. The saving grace is that very little power is needed, so I shouldn't have to spend a ton of money trying different amps.


That being said, are there any specific models of (unmodified) amps people have had success with?


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## Elgrosso

thehatedguy said:


> I have my whole system on my Soundigital GaN fet amps right now. I do have some gain hiss, but I think it is from my Helix DSP Pro.


 So how does it sound?





ErinH said:


> Two major factors:
> 
> The SNR of the amp at 1w. Most manufacturers don't provide this and the ones who do show a rating in the 80's. Instead they only provide the SNR at rated power (which typically is > 100dB). However, this spec is terribly useless when it comes to having high sensitivity drivers. You care about the SNR with little/no power applied which would be captured by a "SNR at 1w" type spec.
> The sensitivity of the drivers. If you have a compression driver with 110dB sensitivity then pretty much any noise is going to be amplified. If your drivers are in the mid-90's you may get some noise but it won't be as bad. And if you have a driver in the 80's then the SNR of the system (amps, headunit, dsp, whatever) will probably not be noticeable (unless the SNR is way below the sensitivity of the drivers).
> 
> 
> I've run in to this issue with both my HT setup and in my recent car update. The amps I'm using for home are Crown XLS v2 and in the car I am using the JL Audio XVi amps. Both are perfectly acceptable for mid-sensitivity drivers (upper 80's to 90dB sensitivity). However, with my high sensitivity compression drivers (HT drivers are rated at >110dB and my new car drivers are 110dB) there's noise floor in both cases. I can't really fault the amps, per se, because I doubt the manfucaturers were designing them for these particular cases with uber-sensitive drivers.
> 
> With my HT I just deal with it since I don't use it as a critical listening room. The sounds of the movies override the hiss, I'm far enough away that it's not really bothersome, and I just don't want to pony up the cash for a home amplifier for 3 channels (L/C/R).
> 
> But for my car, I had to do something about it because it was unnerving. So a friend pointed me to and I ordered a Soundstream Reference 300 amp that had been modified by Gordon Taylor. The information Gordon provided said the amp's original SNR at 1w was 84dB which is pretty commonplace even today (15+ years later). Gordon modified the amp to be used specifically with compression drivers and tweaked it to be 100dB at 1w. That solved my noise floor issue entirely and now my system is completely noise free; even with my higher sensitivity midranges powered off the XVi amp.
> 
> All that to say this:
> I don't think the problem is inherent in Class D amps. Based on my research most amps have an SNR in the 80's at 1w; even some of the nicer Class AB amps. When it comes to compression drivers you don't care about the "SNR at rated power"; you'll never provide a 110dB sensitivity driver with 100 watts in your car so that spec is totally useless to you. You care about the SNR with little/no power applied which would be captured by a "SNR at 1w" type spec. So keep your eyes peeled for that. And good luck with getting that info. You'll probably have to email manufacturers to ask them what that spec is and IME you may not get a reply back at all. Which means, unfortunately, some dice rolling. Or finding a modified one like I did.


Interesting, so maybe I should keep my 3/5/700 serie for later just in case 
Do you know what adjustment was made, something with the biais?





POLKAT said:


> It's crazy that even a Reference 300 was noisy with compression drivers. Cs90ss' advice of trial and error with amps may be the best way for me to go, considering that specs can indeed be misleading. The saving grace is that very little power is needed, so I shouldn't have to spend a ton of money trying different amps.
> 
> 
> That being said, are there any specific models of (unmodified) amps people have had success with?


Of all amps I tried on my horns only a few had a very low noise, steg msk, pioneer a900 and jl hd600, so AB and D. Everything else had some, from acceptable to just too much.
For the dsps, the 6x8 had less noise than the 8x12, but I used a trick on the 8x12 to lower it to even less than the 6x8, by using two outs per compression driver (I was told to not try that but it worked, something related to impedance, didn't understand ).
But the 2x8 is much cleaner on this, with the steg, only way to know if the system was ON was to look at my HU.


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## ErinH

Elgrosso said:


> Interesting, so maybe I should keep my 3/5/700 serie for later just in case
> Do you know what adjustment was made, something with the biais?


With Gordon saying the SNR at 1w before being modded was 84dB, if you were running what I am you'd want to have it modified. 84dB is fine for normal sensitivity drivers but not for mine. 

Not sure how the adjustment was made. The guy I bought the amp from sent me an email that Gordon had sent him and I don't think it said how the adjustment was made. Just that it was tweaked to go from 84dB at 1w to 100dB at 1w.


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## Hillbilly SQ

I've heard that summing outputs can be bad for the processor but never understood why.


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## Jscoyne2

Hillbilly SQ said:


> I've heard that summing outputs can be bad for the processor but never understood why.


http://www.rane.com/note109.html

Sent from my SGH-M919 using Tapatalk


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## ca90ss

POLKAT said:


> That being said, are there any specific models of (unmodified) amps people have had success with?


I ended up with a Focal FDP 6.900 in my daily driver and have been happy with it especially compared to the Focal FPX 4.800 which was one of the worst I've used. The pair of Arc xdi 1200.6 in my other car are about average, more noise than the other car but not terrible. I've been through a lot of amps though, easily over a hundred and most fall into the average category.

A few that I can remember

Audio Art 140.4 above average and the only amp I can think of where the noise is the same regardless where the gain is at
Monolithic Pa-700 and Pa-2400q slightly better than average
Xtant 202m better than average
PPI several older models average to slightly above
Soundstream D and MC series amps average
Sony Xes-M3 average
Mcintosh MC425 and MC427 average
Genesis profile 5 and 2 average
Arc mini below average
JL slash average
Lanzar Opti HC below average
Planet audio BB below average
Phase Linear .4kw average
Gladen RC series average to slightly below



I'd be curious to see what was done to Erin's amp, it's been my experience with the older amps I've messed with a simple opamp upgrade is all that is needed to get acceptable noise levels. 

Gain setting is also very important and takes a bit of trial and error. Just keeping the amp gain at minimum isn't always the best choice. The hu and processor can also add noise and having to turn the hu or processor levels up too high to compensate for the amp gain being at minimum can create more noise than just turning the amp gain up a little.


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## Elgrosso

Jscoyne2 said:


> Why Not Wye?
> 
> Sent from my SGH-M919 using Tapatalk


I forgot to add, I used 4 inputs on the amp as well, then bridged, so I guess in fact it was all fine.


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## ca90ss

Another thing I forgot to mention, with class d amps placement can also be important. I had a pair of amps that were ok when used side by side but when stacked on top of each other developed quite a bit of noise. Never experienced that with an a/b amp.


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## ErinH

ca90ss said:


> Another thing I forgot to mention, with class d amps placement can also be important. I had a pair of amps that were ok when used side by side but when stacked on top of each other developed quite a bit of noise. Never experienced that with an a/b amp.


Yea. And Class D amps do seem to have more susceptibility to RF noise from things like fuel pumps, a/c motors and other things. You'll notice a lot of people running Class D amps mentioning poor(er) radio reception, depending on the placement of them. When I had my old HD amps under the front seats the radio reception was tolerable but not as good as when I moved them to the back of the car, further away from the headunit.

Of course, noise issues like this are always going to depend on the install and the car itself. Hondas are NOTORIOUS for noise issues such as bad RF caused by the fuel pump. I've known people that have done things to the fuel pump wiring to reduce the RF on them. It seems Chad did posted about it a long time ago.


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## nadams5755

i have a couple of focal fdp 6.900s like *ca90ss*, i'm pretty happy with them. my car's got a radio antenna array in the rear window, my radio reception is pretty terrible since replacing my old soundstream ref amps in the hatch. 

i suppose i could also try to replace the tint with ceramic stuff but i don't listen to the radio much.

i wonder what a faraday cage around the amps for broadcast radio wavelengths would look like. :worried:


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## ErinH

ca90ss said:


> I'd be curious to see what was done to Erin's amp, it's been my experience with the older amps I've messed with a simple opamp upgrade is all that is needed to get acceptable noise levels.


This is the only info I have. Gordon is currently on vacation so I'll have to wait to ask anything more.



> The 300 is now set up for horns - I've dropped the power amp gain to improve signal to noise ratio which is now nudging 100dBA reference to 1 watt. As standard this was around 86 so the 14dB improvement is around a 30x reduction in noise.
> 
> The preamp gain has also been reduced so you should be able to match levels with your midbass drivers when fed from a similar signal level. It's got one of the new LME chips in the preamp too and bipolar caps.
> 
> The distortion level at 1 watt is an infintessimal 0.0016% as it's still mostly running in class A at that point. 1 watt equates to pretty high sound levels with horns ( 106 - 110dB spl) so any distortion won't be coming from the amp, and at anything but extreme listening levels you will be enjoying the warmth of Class A through the horns.
> 
> I put new connection screws in the 300 as the old ones were rusty and burred. And some pretty blue led's...


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## Jscoyne2

A Faraday cage around your amps. You can tell people its a grill. >. <

Sent from my SGH-M919 using Tapatalk


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## ca90ss

ErinH said:


> This is the only info I have. Gordon is currently on vacation so I'll have to wait to ask anything more.





> The 300 is now set up for horns - I've dropped the power amp gain to improve signal to noise ratio which is now nudging 100dBA reference to 1 watt. As standard this was around 86 so the 14dB improvement is around a 30x reduction in noise.
> 
> The preamp gain has also been reduced so you should be able to match levels with your midbass drivers when fed from a similar signal level. It's got one of the new LME chips in the preamp too and bipolar caps.
> 
> The distortion level at 1 watt is an infintessimal 0.0016% as it's still mostly running in class A at that point. 1 watt equates to pretty high sound levels with horns ( 106 - 110dB spl) so any distortion won't be coming from the amp, and at anything but extreme listening levels you will be enjoying the warmth of Class A through the horns.
> 
> I put new connection screws in the 300 as the old ones were rusty and burred. And some pretty blue led's...


Thanks. Doesn't look like he had to do anything too extreme. Probably easier to get away with a lower preamp gain in an older amp since they don't require as much input voltage to reach rated power at minimum gain to begin with compared to newer amps that generally take 2-4x the input voltage at minimum gain to reach full power. As long as you can get away with keeping it at minimum gain I would bet that is the biggest contribution to the better SNR with the opamp probably right behind. Hard to tell if he adjusted the bias any or if that's what it was to begin with.

Any idea on what the cost of the mods was and if this is a service he offers or just a one time thing?


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## ca90ss

nadams5755 said:


> i wonder what a faraday cage around the amps for broadcast radio wavelengths would look like. :worried:


I wonder if something like this would work
https://zippertubing.com/materials/shielding/cloth-shielding/z-7200-c


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## ErinH

ca90ss said:


> Thanks. Doesn't look like he had to do anything too extreme. Probably easier to get away with a lower preamp gain in an older amp since they don't require as much input voltage to reach rated power at minimum gain to begin with compared to newer amps that generally take 2-4x the input voltage at minimum gain to reach full power. As long as you can get away with keeping it at minimum gain I would bet that is the biggest contribution to the better SNR with the opamp probably right behind. Hard to tell if he adjusted the bias any or if that's what it was to begin with.
> 
> Any idea on what the cost of the mods was and if this is a service he offers or just a one time thing?


I honestly don't know. When it comes to amp design/modifications I'm not well informed on that topic at all. 

I would imagine it's a service he offers pretty openly. I hope to talk to him a bit about this topic when he's available again. So I'll ask if you want me to. I'll probably send him some other things to modify if he thinks it's worth the effort.


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## thehatedguy

My car? I think it's the best setup that I've ever had, or will have the potential to be as it hasn't had much in the way of tuning past level adjustments, some XO work, very rough delay. The only EQ was mostly by ear.

The stage is high and wide, nothing sounds like it is coming from down low. The bass is all on the dash even with the 100 hertz XO points. And it can get LOUD. I mean standing at the front row of a metal concert loud. I haven't heard a SQ car that could get this loud in a long long time...it is pure brutally loud when it needs to be. There is no power compression...it just gets louder as you turn it up.

A guy from another shop asked me what tweeters did I have in my factory locations. 

None.


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## fish

thehatedguy said:


> My car? I think it's the best setup that I've ever had, or will have the potential to be as it hasn't had much in the way of tuning past level adjustments, some XO work, very rough delay. The only EQ was mostly by ear.
> 
> The stage is high and wide, nothing sounds like it is coming from down low. The bass is all on the dash even with the 100 hertz XO points. And it can get LOUD. I mean standing at the front row of a metal concert loud. I haven't heard a SQ car that could get this loud in a long long time...it is pure brutally loud when it needs to be. There is no power compression...it just gets louder as you turn it up.
> 
> A guy from another shop asked me what tweeters did I have in my factory locations.
> 
> None.



What all speakers are you rockin' now?


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## thehatedguy

Eric's full sized horns with the NeoComp drivers, JBL 2012h midbasses, and an Acoustic Elegance SBP-15 Apollo.


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## ca90ss

How do you like the 2012's? I have a pair of 2123's that will eventually be going in my doors but it will be a while so I'm wondering if I would be better off looking for a pair of 2012's instead.


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## thehatedguy

They are junk...don't buy them, leave them all to me so I can suffer with them.

Seriously, they are huge...the motors on the 2012Hs are larger than the 2206Hs if that would be a concern. I probably could have fit 2206s in retrospect because of that reason,


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## ErinH

Yea, those JBLs have huge motors on them. Makes me wonder how the heck you managed to get them in your car.

By the way, what kind of enclosure are they in or are they vented (if vented, externally or down the frame rail)?


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## thehatedguy

Frame rail


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## Hillbilly SQ

Jason, make sure I hear your car on Saturday provided you make it! Don't see many horn setups these days and always fun to hear a well tuned horn setup.


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## bassfromspace

Winslow,

Do you have any pics of the midbass venting?


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## thehatedguy

Well...it's not well tuned yet...lol. I will try to make it. I had bilateral hernia surgery yesterday and sore as crap right now.

The only venting is with a preexisting hole in the frame rail. There are other holes down there but I sealed them up with some damping mat.


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## bassfromspace

thehatedguy said:


> Well...it's not well tuned yet...lol. I will try to make it. I had bilateral hernia surgery yesterday and sore as crap right now.
> 
> The only venting is with a preexisting hole in the frame rail. There are other holes down there but I sealed them up with some damping mat.


Sorry to hear about the surgery, but hope you get well soon.

Do you remember the approximate size of the hole? I'm thinking of doing a similar set up to yours. Also, did the lack of aiming work as far as your midrange is concerned?


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## thehatedguy

I think is about a 2.5" square.

I wasn't worried about aiming once I decided to go with the modified big bodies since I cross them at 800 hertz.


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## nyquistrate

thehatedguy said:


> Eric's full sized horns with the NeoComp drivers, JBL 2012h midbasses, and an Acoustic Elegance SBP-15 Apollo.


After limited googling, is that 2012H an 8 Ohm driver?




ca90ss said:


> . . . I've been through a lot of amps though, easily over a hundred and most fall into the average category.
> 
> A few that I can remember
> 
> Audio Art 140.4 above average and the only amp I can think of where the noise is the same regardless where the gain is at
> Monolithic Pa-700 and Pa-2400q slightly better than average
> Xtant 202m better than average
> PPI several older models average to slightly above
> Soundstream D and MC series amps average
> Sony Xes-M3 average
> Mcintosh MC425 and MC427 average
> Genesis profile 5 and 2 average
> Arc mini below average
> JL slash average
> Lanzar Opti HC below average
> Planet audio BB below average
> Phase Linear .4kw average
> Gladen RC series average to slightly below



I had CD2v2 on ID full bodies fed from an XTANT 2200i. The i series was their best SQ amp, though I don't know that any were bad. Do you have any expereince with that amp to compare with your list?


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## minbari

POLKAT said:


> Has anyone had any issues using Class D amps with HLCD's?
> 
> First and foremost, when it comes to amps, I am firmly in the camp of Class D sounding just as good as class AB.
> 
> That being said, I've seen a few people say that Class D amps can be "noisier" than their AB counterparts and, high-sensitivity HLCD's can make that noise stand out.
> 
> Is there any truth to this or is this just a case of some people being fundamentally against using Class D amps for anything other than subwoofers?
> 
> Thanks!


older post, but thought I would throw in my $0.02

the biggest problem I found when I had my HLCDs was not so much noise. but because I was running Class A/B and the senstivity is 112 db at 1 watt, you are generally listening to music at considerably less wattage than 1. 

this causes the amplifier to operating in the zero-cross region all the time! with a 1.4 volt dead space between the 2.8 volts that make up 1 watt at 8ohms, this meant that half the signal was dead air.
I solved a little of this by running a 16 ohm resistor in series with the horn driver. this meant that you need about 150 watt/ch amplifier to get 25 watts out of it, BUT 25 watts into a horn that loud is plenty.

I know a Class A would be the best solution, but would burn my car down. I just wonder if a class D would have better results?


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## Mic10is

my old set up was JL HD with horns. no issues. sounded good. did well in comps


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## dcfis

thehatedguy said:


> Eric's full sized horns with the NeoComp drivers, JBL 2012h midbasses, and an Acoustic Elegance SBP-15 Apollo.


That sounds amazing! Wish I could hear that


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## fohrums

ca90ss said:


> (in order to know what amplifier was good whether it's a high end Class D or an A/B I just) took a horn to the stereo shop and tried a bunch of amps and bought the quietest one.


I'm surprised shops allowed you to do that. BTW What horn are you saying here?


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## nyquistrate

Would the Alpine PDX series (claim ultra low noise at 1 Watt) work better than the Arc DXi amps on horns?


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## ErinH

nyquistrate said:


> Would the Alpine PDX series (claim ultra low noise at 1 Watt) work better than the Arc DXi amps on horns?




I just went to the site for the Alpine PDX-V9 5 channel amp and saw what you’re talking about:
“These amps are capable of unheard of S/N ratios up to 95dB S/N @ 1W”

That’s impressive. Really impressive.


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## nyquistrate

ErinH said:


> I just went to the site for the Alpine PDX-V9 5 channel amp and saw what you’re talking about:
> “These amps are capable of unheard of S/N ratios up to 95dB S/N @ 1W”
> 
> That’s impressive. Really impressive.


Do you know of anything with better numbers that I should consider? My Xtant 2200i are a little big to put in the WRX.


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## bbfoto

ErinH said:


> I just went to the site for the Alpine PDX-V9 5 channel amp and saw what you’re talking about:
> “These amps are capable of unheard of S/N ratios up to 95dB S/N @ 1W”
> 
> That’s impressive. Really impressive.





nyquistrate said:


> Do you know of anything with better numbers that I should consider? My Xtant 2200i are a little big to put in the WRX.


I'm obviously late in replying to this, but this is just one of the reasons that I'm still a fan of the 2nd Gen Alpine PDX amps. Too bad they are being phased out and discontinued. 

Without going uber high-end and/or Class A, I doubt you'll find many other amps with these low noise levels at low output.

This was also just one reason I was disappointed in the new JL VXi amps as compared to their HD lineup.

My modded Arc 4150cxlr is pretty darn quiet, too, so if you can find one of those in decent shape grab it, though you'll want to have it thoroughly checked out by a skilled tech before powering it up. Not sure if those would fit in your WRX though if you still have it. They aren't exactly huge, but they aren't compact either.


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## nyquistrate

bbfoto said:


> ErinH said:
> 
> 
> 
> I just went to the site for the Alpine PDX-V9 5 channel amp and saw what you’re talking about:
> “These amps are capable of unheard of S/N ratios up to 95dB S/N @ 1W”
> 
> That’s impressive. Really impressive.
> 
> 
> 
> 
> 
> 
> nyquistrate said:
> 
> 
> 
> Do you know of anything with better numbers that I should consider? My Xtant 2200i are a little big to put in the WRX.
> 
> Click to expand...
> 
> I'm obviously late in replying to this, but this is just one of the reasons that I'm still a fan of the 2nd Gen Alpine PDX amps. Too bad they are being phased out and discontinued. <img src="http://www.diymobileaudio.com/forum/images/smilies/frown.gif" border="0" alt="" title="Frown" class="inlineimg" />
> 
> Without going uber high-end and/or Class A, I doubt you'll find many other amps with these low noise levels at low output.
> 
> This was also just one reason I was disappointed in the new JL VXi amps as compared to their HD lineup.
> 
> My modded Arc 4150cxlr is pretty darn quiet, too, so if you can find one of those in decent shape grab it, though you'll want to have it thoroughly checked out by a skilled tech before powering it up. Not sure if those would fit in your WRX though if you still have it. They aren't exactly huge, but they aren't compact either.
Click to expand...

Thank you for that info on the Arc and verification on the second gen PDX. For anyone else reading, the V9 has good numbers but the low power (1 Watt) specs keep improving as you step down in power. i.e. the F4>F6>V9 for SNR

I did find some new PDX amps after posting my question but they're mostly only available used now.


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## Mic10is

using Arc X2 1000.6 in my wifes BMW on Eric's Mini horns with Neo drivers and Stevens Audio 6.5
sounds good, no issues, no noise


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