opaqueice;172033 Wrote: 
> My question was just why amplitude and not power - I would guess that
> human perception of distortion scales more closely with the power than
> with the amplitude, but perhaps that's wrong.
> 
> I don't understand what you're saying in your post.  That tube amp has
> 5 times more distortion amplitude (-45dB), or 25 times more distortion
> power, at 1/10 of a watt.  Extrapolating the A500 distortion (which is
> quite linear on the log-log plot from a few watts down) to lower power,
> to get to -45dB you'd have to go down another three orders of magnitude.
> So at .0001 W the two distortions would be comparable, assuming the
> tube amp curve stays flat.  I doubt even the most sensitive speakers
> are going to make much noise at that level.
> 
> Therefore into any speakers the A500 has significantly lower
> distortion, so I don't see why you think it would sound bad.
> 
> EDIT - looking at three different tube power amps, the distortion at
> .1W varies from around .2% to around .6%, so I don't think that design
> is particularly atypical.

I see how you are thinking.
However, you can't extrapolate anything down in level when it comes to
crossover distortion. It's a discontinuity in the transfer curve which
is of equal size regardless of the signal level. It doesn't scale with
the signal. Put a low enough signal in there and it will be 100%
distortion. (Well, depending on exactly how the discontinuity looks.)

I hope that made it clearer?


-- 
P Floding
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