I have no idea if there are any Class A consumer type receivers. I kinda doubt it. And for good reason. All that does is add to the cost, and waste a lot of electricity. Class A doesn't sound any better than more practical designs, if that's what you're getting at.

--Ethan

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are there receiver/amps that have class A bias? if so are they expensive?

Hi Lonebadger992,

Welcome to Stereophile forum. (Updated with tables.)

Yes, there are class A amps (biased for class A operation). All single ended amplifiers are biased for class A operation and many push pull solid state and push pull tube amps are as well.

I don't know if you are familiar with how class A, AB, B differ but I will explain if you wish.

As far as distortion characteristics, there is a difference with class A single ended amps having the highest 2nd harmonic distortion, with other harmonics generally much lower, depending upon the load presented. With pushpull amps, the second harmonic is suppressed while the third harmonic generally the highest. Negative feedback lessens all the harmonics relative to each other and the fundamental in each type of operation, whether class A, AB, or B, but has its own problems.

As far as sound quality, class A is generally considered the purest sounding, especially in the midrange/highs, vs class AB and B (depending upon the bias of AB) which can be adjusted with much leeway. Between single ended SS and tube there are some differences that can get complicated. However, there are very few single ended SS amps. The problem with single ended tube amplifiers are high harmonic distortion, especially 2nd harmonic and higher distortion at low frequencies, and a little lack of bass. However, they do not need a phase splitter stage, so the mid/high frequency purity is often better because other distortions are lessened.

I know the above almost sounds like a contradiction. 2nd harmonic distortion is less heard than higher orders. As an example, here is what RCA Radiotron Designers Handbook states, page 608.

"the weighted values of higher order harmonics are quite appreciable. The values of distortion... are derived from Olson." Here are a few examples.

"Harmonic........Weighting factor

2nd................... 1
3rd................... 1.5
4th................... 2
5th................... 2.5
10th.................. 5

As one can see the higher order of harmonic, the greater the weighting factor, thus more easily heard.

Class A pushpull can sound as pure as single ended if the phase splitter is designed with extraordinary care, which almost no one does correctly. Otherwise the purity suffers greatly. So one has to decide whether to compromise the amount and quality of bass but have great purity using single ended, or use pushpull which has more bass and less distortion, higher power, but often times, but not always, lack of purity.

Receivers are generally of average quality so I doubt that any can take advantage of being operated in class A. Class A is also the least efficient, so the most heat dissipated.

Hope this helps.

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Class A doesn't sound any better than more practical designs ...

No doubt there are numerous members now ROTFLTAO!

I know I am.

Winer, this uber-cynicism, Sgt. Schultz "I hear nothink" crap of your's is just too much.

Rolling and rolling and rolling. OMG!