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previous: Bruce Scott,Why did you use the v... -- 10/7/1999 8:04 AM

Re: Cathode bias questions

10/7/1999 1:55 PM
peter	Re: Cathode bias questions Bruce, can you say more about what you mean by "pseudo class AB"? I converted my home-made faux-Marshall to cathode bias as an experiment. The bias current is about 50 mA per tube. When I drive it hard, the output (on the scope) looks like it has crossover distortion: there is a little horizontal bit in the waveform at the zero crossing. (at small signal levels it is clean and sounds good-- better than it did with fixed bias). When I had it in fixed bias, driving it hard would result in symmetrical clipping, top and bottom, like you'd expect. So is this crossover distortion what you're referring to? Is that normal for a cathode- biased amp? Does it mean I need more or less bias current? thanks, peter

10/7/1999 1:55 PM

peter

Re: Cathode bias questions

Bruce, can you say more about what you mean by
"pseudo class AB"?

I converted my home-made faux-Marshall to cathode
bias as an experiment. The bias current is about
50 mA per tube. When I drive it hard, the
output (on the scope) looks like it has
crossover distortion: there is a little
horizontal bit in the waveform at the zero
crossing. (at small signal levels it is clean
and sounds good-- better than it did with fixed
bias).
When I had it in fixed bias, driving it
hard would result in symmetrical clipping,
top and bottom, like you'd expect.

So is this crossover distortion what you're
referring to? Is that normal for a cathode-
biased amp? Does it mean I need more or less
bias current?

thanks,

peter

Replies:

Dave H. q{ So is this crossover distortion ... -- 10/7/1999 4:10 PM