GaN amps: Peachtree or LSA Voyager?

I see an often quoted limit of 0.1% as being the absolute lowest than can be detected, and I think normally much higher.

@deludedaudiophile If that were primarily lower ordered harmonics that could well be true.

But otherwise that statement is false. The problem, frequently ignored, is that the ear uses the higher ordered harmonics (5th and above) to sense sound pressure. Keeping in mind of course that the ear has about a 130dB range!! -so its keenly sensitive to these harmonics! It also assigns tonality to all forms of distortion.

The higher orders can be only 0.01% or even 0.005%; if not masked by the lower orders, they will cause harshness and brightness. We've been hearing this in solid state amps for the last 60 years, so there are literally millions of references on the web!

We've known since the 1930s how sensitive the ear is to the higher orders (see Radiotron Designer's Handbook, 3rd edition). Its also very easy to demonstrate with very simple test equipment that the ear indeed uses the higher orders to sense sound pressure.

For the most part class AB solid state designs have ignored these facts in pursuit of the almighty dollar over the last 60 years. Of course, back in the 1960-1980s the semiconductors needed to overcome the problem simply didn't exist (and it seems the will to design something properly didn't exist either...). Instead, propaganda was generated to make you think you were hearing something 'neutral'. But its the Emperor's New Clothes; the simple fact is that brightness and harshness is a coloration- its not neutral.

@atmasphere 
 

One thing I don't understand from much of the above discussion....  Is it not possible with both Class d and Class A/B amps to engineer the amp to the lowest possible distortion and then add back enough 2nd and 3rd harmonics to give the amp the degree of musicality desired?  And if so, could a "distortion" dial be added to allow the user to fine tune the sound to their liking?

Is it not possible with both Class d and Class A/B amps to engineer the amp to the lowest possible distortion and then add back enough 2nd and 3rd harmonics to give the amp the degree of musicality desired? And if so, could a "distortion" dial be added to allow the user to fine tune the sound to their liking?

Theoretically, to the former, possibly ’yes’. To the latter, likely ’no’ since such a control would have to modify some parameter of the amplifier that might be critical and not take kindly to such an adjustment.

I wouldn’t hold your breathe for such a thing. Usually designers of solid state are very conscious of the ’numbers guys’ that only look at specs and poo-poo the listening experience, even if the latter is what its all about. So they often try to get the distortion as low as they can and anything that raises it is anathema. There are a few that are careful about how their designs make distortion; Nelson Pass is an example.

@snapsc, would that not be easier to accomplish with DSP?

@deludedaudiophile 

I guess I've thought of amps as being in several varieties of late...

those that are either class a or class a/b operating in class a for a while that are using their class a operation to emphasize the lower orders of harmonic distortion in order to be more musical

those that try to drive distortion as low as possible, Benchmark and some of the class d and ganfet amps come to mind, that feel that any distortion that influences sound is wrong

and obviously tube amps

I've thought of DSP as trying to offset room issues by modifying frequency response and possibly reflections and timing..but not the distortion profile...is this even possible?