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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: RE: Too low plate R value for a triode ? and CCS substitution? posted by JKT on March 22, 2017 at 10:34:17:
To the point I made that 80V seems kind of low, I have a Sun 2A3 amp that I modded with CCS loads for the input and driver stages. I kept the input tube 6SN7 but changed the driver to a 6BX7. Because of voltage constraints I had to run the BX7 at 120V p/k instead of the more usual 250V - 300V. Still, with the CCS load the amp sounded very good; much better that stock. One caveat: as the tube ages the plate voltage will increase (bias current fixed by the CCS and thus the bias voltage across the cathode resistor too). As emission falls plate voltage must increase to maintain bias current. This will "eat" into the signal voltage headroom. This can be compensated for by small tweaks to the CCS (decreasing the current). In my case this is critical, in yours maybe not so much if you have lots of extra headroom to begin with.
"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln
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Follow Ups
- RE: Too low plate R value for a triode ? and CCS substitution? - JKT 14:26:49 03/27/17 (2)
- RE: Too low plate R value for a triode ? and CCS substitution? - Eric Chan 09:11:40 03/28/17 (1)
- RE: Too low plate R value for a triode ? and CCS substitution? - JKT 12:18:56 03/28/17 (0)
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