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In Reply to: RE: If they work properly they don't tick. posted by PaulF70 on May 21, 2025 at 13:08:25:
I've always attributed that difference to crossover distortion.I don't think it is.
Norman Crowhurst pointed out a good 60 years ago that a PP amp with a single-ended input (like a Dynaco ST70) would have a bit of an emphasized 5th harmonic, due to the combination of quadratic and cubic non-linearities.
When most people compare SETs to PP, its exactly that sort of PP amp that is compared. But if you put such amps (like the ST70) on the bench you see there's no crossover artifact.
I have an old EV amp that is claimed to be 'class B' (which, when you really think about it, can't exist easily in the real world; more likely some kind of AB circuit, if not the its actually class C...) and it exhibits no crossover artifact at any power level as low as can be measured.
So Occam's Razor suggests a simpler explanation: its something else. I think its that 5th harmonic not being masked properly.
To get around that 5th harmonic problem the PP amp would have to be entirely balanced or entirely differential; perhaps both. In that way the distortion is more the result of a cubic function, which is IMO vastly superior to a quadratic non-linearity insofar as the human ear is concerned.
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Follow Ups
- I doubt that is due to crossover distortion - Ralph 05/22/2513:05:45 05/22/25 (0)
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