class A sound

tom t

what is the difference between class A sound and other high end class AB amps. those that have heard both,your concluions please. class A amps are very expensive and run hot. what it the big sound difference between the two and also tube amps.

Ferres

I think they have a similar sonic quality to tube amps.

mhardy6647

No crossover distortion; the output devices (tubes or transistors) are biased "on" all the time. In practice (IME), more transparent and neutral, all things being equal (e.g., in the vintage Yamaha amps with switchable Class A/Class AB operating points). Remember that "Class AB" amps are (by definition) usually operating in Class A at low power levels.

See, e.g., http://sound.westhost.com/class-a.htm

http://www.audiokarma.org/forums/showthread.php?t=136479&highlight=class

Ferres

Class A's are some of the best sounding amps out there. I heard one perform before and I can't remember any other amp that sounded as good. My only issue with them is their power consumption.

Face

I have a few McIntosh amps that are AB and they really warm up this side of the house, I couldn't imagine what a full class A would do.

Gaara

I feel like this is to general of a question. Just because a amp is class A doesn't mean it will sound good. It depends on many variables such as your listening habits, your system, and especially the speakers.

I have heard amps of all classes that sound great...it all depends on context. I can't really compare the sound because it wouldn't be fair. I didn't like my Cinenova (class AB) on my Rothschildes, but love my Monarchy (class A). Conversely I think the Cinenova was phenomenal with my LSi7s but the Monarchy leaves something to be desired.

That said it is tough to directly compare the two, especially with such variety in prices, build quality, designs, setups, etc. I always focus on getting the speakers right first and then finding a amp that mates well, whatever the amp's class may be.

Ferres

My opinion is only based on a Unison integrated class A compared to a Nad M3 which was twice the price. The Unison sounded great when it comes to bookshelfs and easy to drive speakers. It was only 100watts.

tom t

thanks for the info guys. concidering the fact that class A amps tend to be very expensive you would think they as a whole sound better. gaara has a good point. how it works with your other equipment is a big factor.

mhardy6647

I agree with the above post, but I'd like to... heh,heh... amplify a couple of thoughts.

The odd/even harmonic distortion bit is related more to single-ended/push-pull topology than to tubes/transistors per se, and there are other bugbears such as whether or not an amp design employs global negative feedback.... but the fun's definitely in listening.

I'll reiterate that there are at least a few amplifiers that allow one to switch between Class A and AB operation oneself. Examples include the Yamaha CA-800, CA-1000, and CA-1010 and CA-2010 integrated amplifiers. Hardware such as these (all fabulous pieces of vintage consumer-grade gear) allow a direct (heaven help me) A/B comparison of Class A and AB with all other variables controlled.

Seek out one of those four amps (all relatively common and not obscenely expensive) and check it out.

zingo

Someone correct me if I'm wrong, but here goes:

A class A amplifier reproduces the entire Sine wave that it receives. Since they are reproducing the entire wave, they are inefficient and therefore get hot. (they basicly dissipate 1 watt for every watt used) A lot of class A amps are tube because of the way that thermionic valves create distortion in both odd and even harmonics. It sounds more musical. A class B amp uses 1/2 of the Sine wave, and an AB uses any amount in between. A class C amp uses less than 1/2 the Since wave, but they aren't very common. Class D amps the the most efficient, because they are a "switching" amplifier instead of the linear design in classes A-C. They alternate between off and on to use the least amount of power and utilize the smallest amount of the Sine wave. However, this "switching" does have a bit of a catch in that it is most effective below 150Hz (the slower wavelenghts). This is why a lot of subwoofer amplifiers are class D. A newer amplifier has also come on the market receintly called class T. These are a tripath class D amplifier.

Price only has to do with the design of the amplifier. "Class A" is not a dollars rating. There are plenty of expensive class A amps and class D amps. Over-all class A will be the most expensive, but part of that is because they are the hardest to make well.

Yashu

Class B can sound good, if the design takes into account how their transistors perform... see, when you take a sinewave to a B circuit with no correction, what happens is the wave will have a notch in the middle since transistors' performance is not linear close to 0v. Modern B designs account for this and so they can sound very good. I think class AB is probably the best compromise. Class A transistor amps seem to always need service... the heat and current puts a ton of stress on the components.

phipiper10

Geeks!:p Or are you guys just smarter than me...hmm

heiney9

tom t wrote: »

thanks for the info guys. concidering the fact that class A amps tend to be very expensive you would think they as a whole sound better. gaara has a good point. how it works with your other equipment is a big factor.

In general if a manufacturer is going to the trouble to produce a true Class A amplifier you can bet it's designed to sound exceptional; however there's no way to be sure it will sound as good as it can in your system. Synergy is still the key in many siutations and trying several different components is always a good start.

For me, I will be Class A all the way very shortly. (can anybody say Nelson Pass Aleph)

If it weren't for recent high dollar car repairs and the Holidays I'd already have one

H9

reberly

Just wondering how you know what class your amp is if the specs don't tell you. Is there something else in the ratngs that might give you a clue. For instance I have parasound HCA1500A and 1200 II amps. Could someone tell me what class that would be? I plan on going to my local high end dealer and asking to demo some amps that might be of different classes just to get an idea of what you all are talking about.

Thanks

Yashu

Google? AudioAsylum? Don't know... it's weird that there would be no documentation anywhere. Find a good review on your amp, it may say. The stereophile reviews on my NAD stuff say my pre is class A, and my amp is class B, though the documentation on my pre also says it. The amp, it doesn't say, but a little net searching says it's B.

I would just try to google it, but you can also guess by looking at the amp. If it is small and very cool running even under load, it might be a D. If the case is a little warm and heavy, maybe a B. Class A poweramps are huge and heavy, and A/B are pretty big and heavy too, and they both get very hot.

EDIT: parasound HCA1500A, Class A/B. The other one, dunno... how big/heavy is it and how hot does it get?

reberly

Thanks Yashu.

SolidSqual

A class A amp is not the same as Class A rating by Stereophile.

mhardy6647

The Parasound amps are almost certainly class AB.
e-mail 'em and ask 'em.

heiney9

reberly wrote: »

Just wondering how you know what class your amp is if the specs don't tell you. Is there something else in the ratngs that might give you a clue. For instance I have parasound HCA1500A and 1200 II amps. Could someone tell me what class that would be? I plan on going to my local high end dealer and asking to demo some amps that might be of different classes just to get an idea of what you all are talking about.

Thanks

True class A amps tend to be as heavy as a boat anchor, expensive, run extremely hot. Your Parasound is NOT class A; it's a class A/B design which is the most common type.

The quick and dirty on class A/B amps is that they run in class A up to a point usually about 5 watts or so and then switch to A/B mode. Get your Google on if want to know a more in depth discussion.

A/B amps are more efficient (not nec a good thing but it can be) and are a lot less $$$ to manufacture.

H9

P.s. Yamaha's quasi-Class A amplifiers don't count and aren't true Class A. It's a "trick" circuit which tries to mimmick class A output.

mhardy6647

The old Yamaha amps did indeed offer switchable low-power, true class A operation (e.g., the CA-1010):

FEATURES
Bimodal power amplifier coupled with a fully featured state of the art preamp, separable by switch on the rear panel. Power and impedance specs are quite conservative - the amplifier will drive down to about 3.3 Ohms in class AB and below 2 ohms in class A. Class A power output measured nearly 24WPC into 8 ohms, and class AB measured at 128WPC into the same 8 ohms.

see: http://www.thevintageknob.org/YAMAHA/CA1010/CA1010.html

heiney9

mhardy6647 wrote: »

The old Yamaha amps did indeed offer switchable low-power, true class A operation (e.g., the CA-1010):

FEATURES
Bimodal power amplifier coupled with a fully featured state of the art preamp, separable by switch on the rear panel. Power and impedance specs are quite conservative - the amplifier will drive down to about 3.3 Ohms in class AB and below 2 ohms in class A. Class A power output measured nearly 24WPC into 8 ohms, and class AB measured at 128WPC into the same 8 ohms.

see: http://www.thevintageknob.org/YAMAHA/CA1010/CA1010.html

Yes, I know about how it works and I've also read all the debate about Yamaha's circuit at AK, etc. It's a big, fun debate but as a purest, it's not true Class A. Certainly a noteworthy mark in the history of amp design but hardly in the same class (no pun intended ) as the "big boys".

That's all I'm going to comment on because it wasn't my intention to spark the "yamaha Class A" debate. For furthur reading on the subject (for those interested) please visit www.audiokarma.org It's been beaten to death over the years by die-hard Yammy-ophiles :):)

H9

mhardy6647

I am unaware of a debate on the 1970s Yamahas, so I'll have to look into this...

EDIT: I'm coming up dry at AK. I did find this, from someone with one post !?!
and thus offered strictly "as-is":

http://www.audiokarma.org/forums/showpost.php?p=1162343&postcount=6

Perhaps you can provide a link to other posts on the topic?

heiney9

mhardy6647 wrote: »

I am unaware of a debate on the 1970s Yamahas, so I'll have to look into this...

I realize the specific model you have is a bit older than than the "Auto Class A" Yammy's of the early 80's and that's what people seem to debate about at AK. But from a manufacturer's POV they are similar designs with similar goals in mind.

Debate may be too strong a word...........how about vigorous discussion .

H9

mhardy6647

The Class A bit is pretty simple. If it's more than low-double-digit watts per channel, and you can afford it, it's some sort of "adaptive bias" scheme (e.g., Technics "New Class A") and not operating at gen-u-ine class A bias points.

The 1970s Yamahas are low power indeed at Class A operating points, and they run hot as all getout in that mode. My CA-800, for example, is rated for (IIRC) 15 wpc in Class A (maybe even less).

When it's all said and done, though, I prefer Class A amps that glow in the dark...

nms

Forgive my ignorance, but what is "class A"?

Thanks

heiney9

mhardy6647 wrote: »

When it's all said and done, though, I prefer Class A amps that glow in the dark...

Nothing wrong with that .

For me I prefer a balanced pure class A SS design and perhaps a bit of the designer's philosophy that goes along with it. Always been intrigued by Nelson Pass and his audio trials and journey. I believe very much in his approach to designing a superb and simple circuit w/top notch parts. For me it's the WHOLE package, not just the parts on pcb.

Atleast that's my next move up.

H9

mhardy6647

Nelson Pass has produced some wonderful things (and still does).
Best of all, he shares some his ideas for the DIY (read: cheap -- and/or dirt-poor) crowd, too!

www.passdiy.com

Face

nms wrote: »

Forgive my ignorance, but what is "class A"?

Thanks

This was posted above.
http://sound.westhost.com/class-a.htm

sucks2beme

My Audio Research vt60 manual says it operates in "enriched A/B".
I would say it means it sounds good. Yes, it's a very good heat source.

Yashu

A class A amp is not the same as Class A rating by Stereophile.

What does that have to do with amplifier topology? I said Stereophile confirms the topology as class B for the amp section I have, and their review of the C160/C162 (I am pretty sure they did the review) confirms class A operation... the documentation with the preamp also confirms this.

My amp's documentation does not say, but in the measurements section of the review they clearly state that the amp is class B. They give class B amps 1/3 max clipping power for 60 minutes.

heiney9

Class B amps are not ideal for audio use so I doubt your amp is full class B. If it is it's not ideal for audio reproduction as I know of no suitbale audiophile components that are full class B. They are mostly used for communication switching.

Most pre-amps worth any salt have a full regulated class A front end. It's very easy to do as the "front end" only requires a very small amount of power, thus it's economical to incorporate as well as needing minimal heat dissipation. Many very good DAC's have a full class A front end as well.

Incorporating a class A front end is much easier and less expensive than having full class A for the amplifier output stage.