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In Reply to: RE: Fixed, cathode, and back bias posted by Naz on December 29, 2014 at 23:25:55:
DAC, I think we are describing different animals here. I'm talking about an output stage run as a "Long Tailed Pair". Not a class AB1 cathode biased output stage (you mentioned bypass caps across the CCSs). With a LTP there is no bypass cap on the "tail" impedance. It is impossible with this arrangement for one tube to conduct when the other is cut-off. Thus it runs only in Class A.
As to any current source based on the LM317, I would suspect that it would be noisy (I once tried a LM317 based CCS as a plate load in a line stage and the output had a lot of white noise in it.) If you are looking for a cathode CCS that can handle a lot of current without oscillating try one based on a TL431 (a precision shunt reg. See data sheet for an example of this) and a power MOSFET. Just use a current source to bias the 431 instead of the resistor shown.
"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln
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- RE: Fixed, cathode, and back bias - JKT 12/30/1415:09:52 12/30/14 (0)
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