# Who is running A true class A amp on their horns?



## nubz69

I'm curious to know who is running a true class A amp no their horns. I am currently trying to figure out a SMPS to make a pass labs F5 amp for my car but it is slow going. I am also looking at picking up a soundstream reference class A 10.0 amp to try. 

What have you tried? how did it sound? If you aren't using it any more, what did you switch it for and why?


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## azvrt

Not many true class A amps out there, especially for the car environment.

Nevertheless, a 'fake' Class A amp such as a Soundstream WILL sound nice.
Never tried 'm on horns specifically, though. Very nice on mids and highs. Very nice on sub as well. As a matter of fact, very nice in general...


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## nubz69

I know they are as rare as hens teeth but there are a handful out there. I have found that true class A + efficient drivers = bliss. Now I just want it in my car, even if I have to build it.


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## azvrt

Very true. If you really want something special, try a Reference/Rubicon Picasso or a Rubicon Renoir. Not true class A either, but nonetheless.


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## Wesayso

Isn't the (old) Genesis SA30 a true class A amplifier?


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## azvrt

No it is not. I've owned SA30/SA50/DA100 and can't recommend them enough. Somehow they match perfectly with the old Altec Lansing carbon speakers, unbelievable combination. But they sound fantastic on most speakers. I didn't like them on certain Focal speakers though.


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## Patrick Bateman

nubz69 said:


> I'm curious to know who is running a true class A amp no their horns. I am currently trying to figure out a SMPS to make a pass labs F5 amp for my car but it is slow going. I am also looking at picking up a soundstream reference class A 10.0 amp to try.
> 
> What have you tried? how did it sound? If you aren't using it any more, what did you switch it for and why?


I've run my best tube amp on my car system by running an extension cord out to the car. I also considered building one of the Nelson Pass Aleph Mini amps for the car. (You should be able to run the Aleph Minis off of a pair of laptop computer power supplies. There's a thread on diyaudio where someone did it, along with a Zalman computer heatsink for cooling the mosfets.)

I switched back to my Tripath amps.

At home I've noticed a very VERY modest improvement in soundstage 'bloom' with a SET, but that's with a set of VERY expensive monitors, and only when listening in 'the sweet spot.'

Get a few feet off-axis and that very VERY modest improvement in the soundstage just evaporates. Which is why that SET was more trouble than it's worth in the car.


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## azvrt

Patrick,

Every time I see your name on this forum some bells are ringing in my mind.
I finally know why, I remember the main character in the 'American Psycho' movie had the exact same name. Little off topic I guess...

All the best.


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## thehatedguy

The closest that I've come to rear class A was a pair of Monolithic Class A monoblocks on my horns. They are extreme high bias a/b and sounded really great.

And I did make a pair of mini Alephs to use in the car. I used the power supplies from the Monolithics to power them. Sounded incredible...but needed more filtering to work in the car- too much ripple in the output. 

I do have my HSS Class A tube amp, but it never got powered up in the car on the horns...it did spend some time powering my home horns though and sounded wonderful.


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## Patrick Bateman

cajunner said:


> this is an extremely odd observation as far as my knowledge of tube amps goes, and does cut across some grains...
> 
> do you have any hypotheses on why you saw the changes in the off-axis, and also are you saying that in a highly reflective environment there was no improvement from the tube sound acting on the signal?
> 
> I find the idea that, whatever magic happens as a result of tubes being used, it is observed to be dependent on the imaging bias to listener positioning, I find that very interesting; and that other more easily recognizable audible artifacts/causal relationships, are passed over for this explanation.


There was a modest (and I mean *modest*) improvement in the imaging of my home speakers with the tube amp. Nothing to get excited about, but it seemed to be there.

In the car, this improvement was basically inaudible because we listen so far off-axis. In other words, the modest improvement of the tube amp was ameliorated by the crummy listening position.

It's similar to wearing glasses; no matter how good your glasses are, if the apex of the lens is not directly in front of your eye, the image is going to be out of focus. You could have the perfect prescription, and *it's still going to be out of focus until you get the geometry right.*

This is why I write these insanely long threads about pathlengths and interaural time differences and psychoacoustics. Until you get the basics right, an expensive amplifier is lipstick on a pig.

http://www.diymobileaudio.com/forum...vanced/60146-creating-perfect-soundstage.html


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## Patrick Bateman

Oh, one quick note on the previous post -

Tube amps can make a lot of compression drivers sound better simply because they roll off the top octave. Compression drivers generally have diaphragms which are much larger than a conventional tweeter. For instance, you can spend $20 on a titanium dome and it will have a peak around 18khz, maybe 20khz. But due to the large diaphragm of a compression driver, *the peak occurs much lower.* Sometimes as low as 10khz.

*So when you pair a tube amp with a compression driver, the rolloff at the frequency extremes can make that compression driver sound sweeter.*

Instead of using a tube amp and large compression drivers, I use solid state amps and small compression drivers. (Celestion CDX-1425) Because the diaphragm is less than half the size of conventional compression driver, that nasty peak is higher in frequency. In addtion, Celestion uses aluminum instead of titanium, which moves the peak up even further.

This comes at a price though - the Celestion can't play nearly as low as a conventional compression driver.

Here's Brandon's measurement of a B&C DE250 - you can see the 'hash' starts to occur around 15khz:








And this is a world class compression driver - much better than 80% of the junk out there.

I've elaborated on how this works here, if anyone is curious:
http://forum.audiopsychosis.com/viewtopic.php?f=8&t=56


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## nubz69

I recently have just finished a F5 amplifier and I also have a Decware Zen Select SET amp that I have used for years. I like them both for very different reasons. For practical purposes I think that solid state class a is the way to go on horns in car. If I could find a SMPS to mate with a pair of F5 boards I would be using that setup now. I just recently found a car SMPS kit that may work with a bit of mods. Once I finish up some other projects and sell some extra stuff, I am going to try building my own F5 car amp for my horns. That is unless I can find a true class A car amplifer to try out that doesn't cost an arm and a leg.


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## Oliver

nubz69 said:


> That is unless I can find a true class A car amplifer to try out that doesn't cost an arm and a leg.



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Made in California for californians ~ If you were to see a pure class A amp for car audio. A pure class A amp will draw close to the same amount of current sitting idle as it would at full power. The last 'almost pure' class A car amp (a Monolithic amp), which ran in class A to something like 25 watts or so before switching to class B, heated up to 184 degrees F sitting on the bench at idle for an hour and sounded simply beautiful as it played "Fugue in D Minor" ~ http://www.youtube.com/watch?v=ipzR9bhei_o


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## The A Train

I dont see how a true class A amplifier will ever be suited for the car environment unless you live somewhere that its almost always cold, like Alaska. With a maximum efficiency of 25%, there will heat; and lots of it. You will have to have a serious heatsink, fans, water cooling etc for it to run at proper temperatures.


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## S3T

Actually, in-car water cooling isn't a big issue, as there already is the engine cooling system


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## nubz69

Heat isn't that hard to manage in a car especially if you have a trunk. If you have your amps in a trunk there is no problem using fans on a heat sink. Even a small fan will make a heat sink way more efficient. Just look at computer heat sinks.


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## The A Train

nubz69 said:


> Heat isn't that hard to manage in a car especially if you have a trunk. If you have your amps in a trunk there is no problem using fans on a heat sink. Even a small fan will make a heat sink way more efficient. Just look at computer heat sinks.


this may be true, but class A amps are generally used for very small outputs; generally less than 1w.


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## Oliver

> Made in California for californians ~ If you were to see a pure class A amp for car audio. A pure class A amp will draw close to the same amount of current sitting idle as it would at full power. The last 'almost pure' class A car amp (a Monolithic amp), which ran in class A to something like 25 watts or so before switching to class B, heated up to 184 degrees F sitting on the bench at idle for an hour and sounded simply beautiful as it played "Fugue in D Minor" ~





ameuba10 said:


> this may be true, but class A amps are generally used for very small outputs; generally less than 1w.


*Beauty is in the ear of the beholder*


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## Oliver

Genesis Dual Mono Class A

Introduction for those who are not aware what this Class A amp is capable of!

Long considered the ultimate configuration for superb audio performance, true class A amplification has been passed over by the automotive world due to cost and current consumption. Cleverly integrating Class A and Class G technology, Genesis has managed to produce a ground breaking product which operates in true class A mode up to 20 Watts per channel at 4 Ohms then seamlessly switches to class G for high power requirements – up to 150 Watts per channel. As a result, idling current is kept below 15 Amps.



> The Monolithic amps were Class AB high biased to drive class A like the SS amps, And If I recall properly they did not live long and happy lives, or like 2 ohms either. I know someone that has several mint examples of these in his collection. Nice and very hot high bias amps. Pricey too as I remember. As for "True Class A" well I saw that wording a lot over the years. I guess that all depends on if you accept a class AB output stage being biased into A class mode as "True" class A.


http://www.amazon.com/dp/0890064792...e=asn&creative=395093&creativeASIN=0890064792

GuideCircuit : 36 W Class-H Car Audio Power Amp

Car Amplifier Circuit Schematic using TDA2040 Integrated Audio Amplifier



> Given below is a car stereo amplifier circuit using audio amplifier IC – TDA2040
> Description of the circuit:
> 
> A car stereo amplifier circuit using TDA2040 is shown here. TDA2040 is a monolithic integrated audio amplifier that operates in Class AB mode. The IC has built in circuitry for short circuit protection and thermal shut down and more over it can be operated from a single supply too. The amplifier can deliver 12 watts into to a 8 ohm speaker.
> 
> Notes.
> 
> *
> Quality of the PCB is a very crucial factor in the amplifiers performance.
> *
> The amplifier can be operated from cars 12V line.
> *
> Heat sink is necessary for TDA2040.
> *
> All electrolytic capacitors must be rated 15V.
> *
> Only one channel is shown here. For stereo application you must make one more identical copy.


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## ecbmxer

> Made in California for californians ~ If you were to see a pure class A amp for car audio. A pure class A amp will draw close to the same amount of current sitting idle as it would at full power. The last 'almost pure' class A car amp (a Monolithic amp), which ran in class A to something like 25 watts or so before switching to class B, heated up to 184 degrees F sitting on the bench at idle for an hour and sounded simply beautiful as it played "Fugue in D Minor" ~


Holy crap, I didn't realize the consumed current like that even at idle! I've always wanted a tube amp for my home system. I need to build a new higher end set of speakers to warrant that though.


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## trojan fan

ecbmxer said:


> Holy crap, I didn't realize the consumed current like that even at idle! I've always wanted a tube amp for my home system. I need to build a new higher end set of speakers to warrant that though.


Speaking of Monolithic Sounds, I used to live in Santa Maria and had a friend who worked there back in the 80's . They were a small company that manufactured some awesome amps, back in the day they were ahead of the times. Anyone have any experience with them, pics, stories......


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## King

I will be running a pair of Adcom 4702's with horns when I finally get around to putting a system together.


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## veritasz34

Well I'm sitting on three old school Alpine 3558 Class A /Class A/B amps..The current draw and size is the reason I'm sitting on them. I have 3 of them and would sell them all if someone was serious about buying..


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## subwoofery

veritasz34 said:


> Well I'm sitting on three old school Alpine 3558 Class A /Class A/B amps..The current draw and size is the reason I'm sitting on them. I have 3 of them and would sell them all if someone was serious about buying..


This is not really the place to sell your products... Especially since you don't meet the requirements to post a sell thread... Please read the classifieds rules. 

Kelvin


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## thehatedguy

Veritasz34...that sounds like a Joe Black screen name.


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## veritasz34

Sorry but I have used this screen name for years..

Also hopefully I'll one day get enough posts to meet your requirements for selling..


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## nubz69

I just picked up a chrome Soundstream Picasso and hooked it up to my horns. It replaces a d200 that was on my horns. Now I just need to get it tweaked and see how it compares.

Does anyone know any worthwhile mods for this amp?


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## azvrt

nubz69 said:


> I just picked up a chrome Soundstream Picasso and hooked it up to my horns. It replaces a d200 that was on my horns. Now I just need to get it tweaked and see how it compares.
> 
> Does anyone know any worthwhile mods for this amp?


I have recently experimented with lots of different op-amps, also on this particular amp. Didn't even hear the slightest bit of difference. At first I thought I did, but it's just the imagination. That's my opinion, and I am a firm believer amps sound different.

Don't waste your time and money and enjoy this amp. You won't find many better amps around, SQ-wise. Different sounding ones yes, so then it's a matter of personal preference, but there aren't many that are better.


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## nubz69

Do you happen to know the proper bias setting procedure for this amp? I would like make sure everything is set properly as I think it may have been repaired at one time.


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## azvrt

nubz69 said:


> Do you happen to know the proper bias setting procedure for this amp? I would like make sure everything is set properly as I think it may have been repaired at one time.


Sigh. Unfortunately I do 
Here we go again. Send me a PM with your email address and I'll send you instructions and pictures as well as the schematics. Hopefully for me, I can find an old mail and copy / paste the text 

You are smart to want to do this. On most high bias amplifiers I have checked the bias of, it was way off.

Is it a Ref or Rubi Picasso by the way ?


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## nubz69

It looks like this guy, which I think is a reference. 

http://i9.photobucket.com/albums/a68/DanTheNiceGuy1/100_0130b.jpg

Which was considered their best, the class A, reference picasso, or rubicon picasso?

Did you try anything besides opamps? Are there trouble parts that should be replaced while I have the amp open?


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## azvrt

This is a Rubicon Picasso. I don't think there should be much difference in sound between a Ref and a Rubi, I'd have to do back to back testing between my Ref Picasso and Rubi Renoir to tell you exactly, but the difference won't be huge, that's for sure.

The Rubicons are more reliable.
If it works, leave it the way it is. Just set the bias, clean the amp, and re-assemble it.
I did not try anthing but op-amps, but I know a guy who did, without results.

I have tried many different op-amps on several amps, nothing. At least, I can't hear it.
I can't hear the difference between a TL07x and a top-spec LME497x0 (LM4562) or Burr-Brown, even OPA627 which is horribly expensive.

In theory, there should be less noise and maybe less distortion, but I can't hear it. And I had an advanced hearing test done by a specialist who told me I have quite exceptional hearing. At first, with the op-amps, I thought I was hearing this and that, but with back to back testing, I soon found out it's all my imagination. I tricked my father, who heard great differences like I thought I did at first, with a blind test and failed it big time.

If there are differences, you won't hear them in a moving car.
People saying this o-amp sounds bright, the other warm, are either hearing things that I cannot, or their applications (other than high end car amplifiers) react differently, I don't know. It was a waste of money for me, not a waste of time since my soldering skills improved a lot. But I cannot hear differences, and this from someone who firmly believes amps sound different.


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