Class A vs. AB vs. D... can you hear a difference?

All things remaining constant is there an audible difference?

I do not mean tube vs. Solid state.

All solid state.

Some Class A amps go to class AB after so many watts... is there an audible change?

I ask because I have a class AB amp and was thinking about going to a class D set up front for home theater


It depends greatly on amplifiers used. To me class D
sounded smoother and less splashy (darker) than class AB.
Midrange was better but lower midrange was leaner (had to
change speaker cables). Lows were tighter while highs
initially sounded less extended, but they just sound
different - cymbals are less splashy. Amplifier (Rowland
102) needed few hundred hours of break-in to sound smooth.
Initially it was a little harsh/forward. This amp also
sounds much better at lower volume (resolution, extension).
At high volume peaks it keeps composure better but it might
be due to regulated (SMPS) power supply and not the class of
I sold a lot of Primare in the past. These days I seldom sell
it. They went from class AB to D. When you compare the old
one with the new, the old ones are more musical and even have
a better 3 Dimensional stage. The Pioneer receivers in class
D sound like shit.

But class D is great for subwoofer amps, and even in some amp
it can be good.

Pass class AB amps sounds great in class A and B.
Having heard a fair sample of all three, in general I would say yes, each group tends to have some similar sonic characteristics as a group that will still vary somewhat in comparison case by case.

Class A is more towards a warmer tube amp sound than A/B. Sound is still more damped however.

Class D also is more towards tube amp sound in the sense of being more liquid in the midrange in particular. Sound is very highly damped but more holographic and neutral to colder sounding in particular than most Class A/B.

Class A/B can vary widely all over the place but tends to be more towards the middle of the others sonic traits in general.
My experience is limited to an A/B and five switching amplifiers including a Pioneer receiver. Overwhelmingly the switching amps didn't become congested when driven hard and were consistently less fatiguing. After repeated comparisons I concluded they're presentations were simply different and I enjoyed them both.

My class D performance improved greatly with upgraded AC (not conditioned) and attention to cabling synergy, something many detractors fail to confront.

The Pioneer receiver's two prong AC improved the most with my homes AC upgrade. In the two channel system the receiver held its own very well with the mono blocks. And like the monos it likes lots of copper strapped to its terminals. I settled on NuForce speaker cable.

Blanket statements regarding switching amplification are a dime a dozen often made without any set up details. Class D is not plug and play and simply another amplifier choice.

General guidelines on a topic such as this has too many variables to offer any useful info. IMHO. I have heard Class A, AB, B, all sound great and terrible. Same for tubes in A, A-AB, etc. Most important is how the amp matches the speakers. PT
Had an 1980s vintage Yamaha CA-1010 Integrated amp for a year, just sold it. 18/18 watts class A then to 90/90 watts class AB. Could not hear "switching" and setting output to "A/AB" sounded better than "AB". More detail/more solid lows. Not a major difference, but surely noticeable.
My system is all bowers and wilkins.
802d htm1 in the front.
802n for the back channels.
804S for expansion chanels.

My amp is am anthem statement p5.

I am looking to add the 804s speakers for 6 and 7 channels.

Short of buying another anthem statement amp. I am looking into other options.

Anthem makes their mono amps. 1000 watts (for me over kill) but it is a class D design.

I had thought about class A.... but I hear of a lot of heat coming from the amps. And I want to be more effienct.

B&W recommends speaker cables with a low ohm per a given foot.

I am not one that believes cables beyond a certain point help or hurt. But then again my ears are not all that great.

So that is the background for my question on amps classes.

I could easily use the anthem for surround channel only.... if I found 3 channels to use up front from another amp or amps.

Bill, for the 6 and 7 channels, just effects, you don't really need another statement amp, but I'd use your 5 channel on the front channels for sure. You could get an Anthem MCA amp or even go to another brand I think. I'd suggest Parasound too, they are voiced similarly to Anthem I believe. Their Classic line would do a fine job, and of course the Halo line, depending on your preference/budget.
Still not convinced with the high frequencies of any class D I've heard, but I've only heard a handful. Could say the same about most tube amps I've heard. Still have concerns about AC pollution of SMPS but that has become universal.

Having a pair of Plinius that can switch from AB to A, which is close to "all other things being equal", I prefer A. However, I could easily live with AB if I didn't have the choice and be joyfully ignorant of the subtle difference.
To me there's a chance that a class D would differ too much with what the Statement amp is doing with the B&W's. Class A is too hot and getting 200 plus wpc would be pretty rare and expensive I think. No point in trying to re-invent the wheel here, stick with what is in the rest of the system, Bill.
There are newer designs of class A operation that does not put off so much heat, with the likes of fans,very low stand by power consumptions and etc.., me, I enjoy the Heat of pure class A operation in big class A older amps, keeps my family warm in the winter, and I appreciate the amp's value more, by thinking of the amp as a jet engine that blows the sound quality out the window with any other class of operation of amps, might not make sence, but I love it!
If they are well made you can not hear the difference.
Ngjockey, you have to realize that linear power supply is in reality a primitive switcher that pollutes AC even more. Jeff Rowland designed his latest class AB power amps with SMPS to reduce noise. For the same reason he designed his Capri preamp with SMPS (where efficiency is not important). Benchmark was able to improve signal to noise ratio from 116 to 126dB by changing power supply from linear in DAC1 to SMPS in DAC2 . Recent power amp from Benchmark is also powered by SMPS. As for the highs in class D, I agree - they sound different, more natural. Brass sounds less splashy and more like brass.
I enjoy the Heat of pure class A operation in big class A older amps, keeps my family warm in the winter

Come on Keith come clean I know you live in Memphis Al.

Just how cold does it get in Memphis during the winter LOL
Ebm wrote,

"If they are well made you can not hear the difference."

Ones assumes you mean if they aren't put together with coat hangers and bubble gum.
I owned class D amplifiers on two occasions, an expensive set of Cary monoblocks being one of them.

First of all, these 500 watts per unit sounded no more authoritative than the 100 watts per side integrated it replaced.

Secondly, even though I wanted to like them, I just could not get used to the sound. Pretty bad experience in my case.
I guess it should be pointed out that I am looking at get peak levels of 105 db. (THX standard)
Hi davehrab, I live in mobile,Alabama, I was being humerous!, However, we did have a bad ice storm here last year that was rare!, we had about a month of below 20 degrees, thats cold to us down here, Honestly, I have no gripes about my amp getting as hot as it does, a none issue for me for the sound quality I get in return, I am happy with, sure there may be better, this is all I need, cheers.
09-01-14: Kijanki
Ngjockey, you have to realize that linear power supply is in reality a primitive switcher that pollutes AC even more. Jeff Rowland designed his latest class AB power amps with SMPS to reduce noise.
this statement was a surprise to me.
can you explain why a linear power supply pollutes more than a SMPS? if it's true, it's certainly contrary to logic....
Linear power supply draws current from the mains in narrow spikes of high amplitude. These spikes contain a lot of harmonics that might induce noise in any LC circuit inside as well as coupling to other cables. I called it a primitive switcher because diodes switch on/off when voltage is the highest. It also produces diode switching noise when diode is suddenly reverse polarized and conducts for a moment in opposite direction to finally snap back. In addition to high frequency noise it also produces 120Hz noise that is very hard to filter out. It requires large transformer that produces mechanical noise especially in presence of any DC. It requires a lot of capacitors to clean 120Hz and to keep voltage steady since it is unregulated. These large capacitors contain inductance compromising amplifier response at higher frequencies. Adding non-inductive capacitor in parallel helps but creates parallel resonant circuit (with inductance of main capacitors) that rings.

Modern zero-voltage/zero-current switching SMPS operate at high frequencies (Rowland latest SMPS operates at 1MHz) that are easy to filter out. In addition they often contain Power Factor Correction presenting resistive load. In addition they are line and load regulated with instant response and are not sensitive to presence of DC (can even operate from DC). Jeff Rowland uses SMPS in preamps where efficiency is not important. Benchmark's new power amp contains ultra quiet SMPS resulting in overall S/N=132dB.

Bel Canto wrote white paper highlighting advantage of SMPS

Jeff Rowland also wrote many papers explaining use of SMPS:
I've owned excellent versions of all 3... I've owned a dozen or so amplifiers in my time and can tell a difference between every amp that I've owned, But I can't say that it because one was Class A... A/B or D... Great amps are available in every class output. I suspect that if you put 3 excellent examples of a Class A, Class A/B and a Class D in any system, most of us would be pretty happy campers.
I currently own a very highly modified Sumo Nine and an amp with Abletec Mono Modules that I built in a stereo case.
Both are very nice... By the way, anyone out there that would like to venture into Class A inexpensively, the Sumo dead stock is pretty good, but proper parts upgrade really make this amp come to like, incredible value.
Overall, I believe that you could make an easy enough argument for tube type or bipolar vs Mosfet or any other output device. Overall, its the design that matters.
I hope this helps, Tim
Bill as you can see objectivity can be hard to come by especially when one loses site of the question.

I really enjoy my home theater. It's a 7.1 system in a smallish space with a Pioneer Elite receiver driving sensitive Triangle speakers and two 10" Velodyne DD plus subwoofers.

I've heard some very expensive HT systems that are simply wasted on the quality of much of the media that's available today. In the end it's just TV with a digital source which doesn't even come close to the elegance of analog two channel. Here is were switching amplifiers make sense because they can be constantly powered without wasting tons of volts. I wouldn't stress the THX standard anywhere near as much as getting the extra low frequency right and having the ability to control the ELF on the fly with remote volume and EQ presets.

If you have enough room effective speaker placement rather than depending on drastic room correction usually results in a better presentation.

My system really came into its own when I went to 7.1 and got rid of the dipoles. The transitions from back to front are much more defined even with 5.1 media matrixed to 7.1.
Bill, I'm very sorry that I wasn't objective and lost site of this question.
"Some Class A amps go to class AB after so many watts... is there an audible change?"

A short answer would be, don't worry, a good representation of Class A, A/B or D could do a good job in your home theater.
It is more how the design is implemented than the class of Amplifier. Check the forums and read a few reviews, you'll zone in on a few pieces very quickly. I'm sure that if you would like to advise if your are thinking a receiver or integrated or seperates, you will get some good advice.
Good Listening, Tim
Tim, Please accept my apologies for what appears to be a comment directed at you as that was not my intention.

Without even thinking that my comments were following yours I didn't mean that YOU weren't objective, rather a portion of the thread in general.

Again my apologies.
in the Threshold S/160 loud, the sound is more dirty, but do not notice changes in dynamics, and precision ... at low volume work in class A, greater volume and less accurate
M-db and Bill, I also apologize, I realized those remarks might or might not at all have been directed at me... I sometimes find this forum quite difficult, we are a bunch of arrogant audio heads, we all know it all. On occasion some new members or less active members find their courage to get involved and post, then out of nowhere they get shot down and that ends their involvement. I'm sure that I am guilty. I've been at this 35 years and have said DUMB things on this forum... I hope he doesn't mind, but the mighty Ralph Karsten once sent me a private email about a post, he was caring that I didn't look stupid... what a gentleman!.. I explained my position to him, he said I was correct and then I re explained correctly on the forum. This is what we need in this this forum.... Sorry for the rant here and M-db, I don't make any of this statement toward you, in fact your points were quite valid. I've seen others slapped several times in other threads just the within past few weeks and its been on my mind. Bill, didn't mean to steal your thread. Good luck. Tim
Yes. Within the same amp, you can tell the difference between A and A/B. Just listen to a Plinius.