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Old 29th Nov 2019, 10:50 am   #19
Alan's MagicEye
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Join Date: Sep 2017
Location: Luton, Bedfordshire, UK.
Posts: 53
Default Re: Building a 5 valve A.C. amplifier from scratch

At the risk of being shot down in flames again��, I personally like the "distortion introduced by single ended triode amplifiers, I am a now an amateur, once professional, (a long time ago) musician. I believe that this is to do with the way that different types of amplifier introduce harmonic distortion?

Here is an excerpt from some research, valid or not, comments welcome...

"It is seen that a SE Triode amp only produces three significant harmonics. Based on listening tests of the fundamental tone plus a single harmonic, the audibility thresholds for the 2nd, 3rd, 4th, 5th, and 7th harmonics are approximately -20 dB, -20 dB, -40 dB, -35 dB, and -50 dB respectively. In general, the higher order harmonics are audible at much lower levels. For the SE Triode amp the 3rd and 4th harmonics are not audible over the range of this figure, and the 2nd harmonic is only audible at a value of alpha of 0.8 or more.

There are no even harmonics for the other two amps.The solid state amp doesn't produce any distortion until the amp clips, but then the levels of the audible distortion products rise very quickly, and the 3rd, 5th, and 7th harmonics are audible for the higher values of alpha. For the push-pull pentode only the 3rd harmonic is audible."

Full article here:
http://www.silcom.com/~aludwig/EARS.htm
And
http://www.silcom.com/~aludwig/Amplifier_distortion.htm

This may also be of interest regarding negative feedback:

http://www.normankoren.com/Audio/FeedbackFidelity.html


I have lit the blue touch paper, now I stand back and admire the firework display

I hope that you find this informative and or amusing.

Alan

Last edited by Alan's MagicEye; 29th Nov 2019 at 11:05 am. Reason: Typo
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