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In Reply to: Re: Question on feedback and transformers posted by Ralph on January 18, 2007 at 08:25:31:
Perhaps a poor choice of words... feedback does not "introduce" odd order harmonics any more than push-pull stages do... even order harmonics are canceled and converted to higher order in smaller amounts. They are only present in the output if harmonics were there without feedback. If they were inaudible without feedback, they will be inaudible with feedback. My own opinion is that harmonic distortion (below 0.5% THD or so) is not a factor in the sound of an amplifier (regardless of the harmonic spectrum)- I think intermodulation is much more audible.The "time shift" due to feedback is of course insignificant if the loop has adequate bandwidth. Phase linearity within the audible range is IMPROVED by feedback. Of course, feedback works best with amplifiers that need it least (and transistor amplifiers need it MOST...).
Some speakers DO sound best with amplifiers with low damping factors - but most modern ones were designed to give the best response with low source impedance amplifiers. I'm not sure than a damping factor above 10 makes much difference, but a triode amplifier without feedback has a damping factor of about 3 (reasonable) and a pentode about 0.2 (awful).
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Follow Ups
- Harmonic distortion is a red herring - Tom Bavis 11:18:13 01/18/07 (3)
- Re: common misconceptions - Ralph 13:17:05 01/18/07 (2)
- Re: common misconceptions - Tom Bavis 14:30:47 01/18/07 (1)
- Feedback gives the amp a second chance to distort - Ray Moth 18:07:43 01/20/07 (0)
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