[Arny Krueger]

"Eeyore" wrote in message
...


John Byrns wrote:

Patrick Turner wrote:

Cancelation of even order harmonics occurs in amps working in class AB
during that part of the wave forms which are in class A, ie, the bits
either side of the zero crossing.

But once each tube moves into cut off, nothing is cancelled.

Patrick, I'm surprised to hear you say this. What are you trying to
tell us, that the even order harmonics are only cancelled during those
parts of the cycle when both tubes are conducting, but that the even
order distortion components reappear during those parts of the cycle
when only one tube is conducting? If you actually believe that you
should go back to the books and study the theory of harmonic distortion
more carefully. I hope you didn't get this notion from the RDH4, I
haven't read the RDH4's harmonic distortion explanation, but if this is
what it says I have just lost any respect I had for the book. In a
perfectly balanced PP amplifier the even order harmonic distortion is
completely cancelled even when the tubes are cut off for parts of the
cycle.

I'd love to know how that happens. There's no cancellation of ANYTHING
once one
side has ceased conducting !

Actually, there is cancellation regardless of whether one side has ceased
conducting or not, because the cancellation comes from the fact that the
transfer functions of the two sides are identical but opposite.

During the portion of the wave where both sides conduct, there may be
cancellation of odd order distortion.

In school I was taught the law of half-wave symmetry. Any wave, no matter
how distorted, that has matching halves has no even-order distortion.

A wave that is composed of one half of any kind and the other half is zero,
has only even-order distortion.