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In Reply to: RE: Has anyone used LM317 as constant current source posted by Leo loves music on April 08, 2025 at 20:37:23
With just 7V to work with, a cascode MOSFET CCS would require a negative PS. What's the bias current? For current less than 10mA I would recommend a cascode NPN BJT CCS. That too would entail a negative PS. My system has 16 long tail pairs; so, I have some experience with CCS tails. IME the higher impedance cascode CCSs are sonically superior.
"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln
Follow Ups:
LM317L should work well with 6SN7.
It will work; just not as well. If you don't want to deal with a negative PS go for it. I have used cascode MOSFET CCS with 6SN7 diff. pairs to good effect.
"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln
Walt Jung published an article in AudioXpress on Current Sources. One of the circuits was a cascode based on the LM-317. Dave Davenport of Raleigh Audio implemented it in his Line Stage kit as a plate load. At the time I had one of his Line Stages and I tried it. It caused a noticeable amount of White Noise. This was due to the LM-317. I don't know how much this would effect its use as a tail impedance; but, as a plate load, unacceptable.
"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln
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