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In Reply to: RE: 6SN7 beta follower : effect of cathode bypass cap lower triode section ... posted by Tre' on April 06, 2014 at 10:51:56
The output level on the graph did not change for the given input signal level, so the gain did not change either.
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Then I would say there's no need to bypass the cathode.The cathode bypass capacitor is intended to prevent local current feedback.
Local current feedback is degenerative. If the gain stays the same, bypass cap or no bypass cap, then that tells me that there is no feedback present which proves that the stage is running constant current.
If the stage is running constant current then a cathode resistor for bias is just as good as LED's or whatever else because all the current is direct current.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 04/06/14
There was a reference to using a depletion mode JFET as a CCS to replace the BJT and it related components in the book.
But the distortion performance of doing this was supposed to be worse.
The only thing left to try is another BJT with greater hfe.
I used a 2N2907A with a hfe = 180 instead of the BC558.
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