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Vintage threads from the first ten years
| previous: Scott After reading Bruce's reply above, ... -- 10/6/1999 2:02 PM |  |
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Re: Cathode bias questions
 10/7/1999 8:04 AM |
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Bruce | Re: Cathode bias questions Scott, Why did you use the variac to adjust the voltage, again? Just to get the apparent plate voltage the same? BTW this is all fine and dandy at idle, but, if you can drive the tubes hard enough, when actually playing, to shut one side shut off during some part of the cycle, the whole self biasing thing gets skewed. The more Ac riding on the bias voltage, the odder it gets. If you never drive the amp hard enough to get into that pseudo class AB1 thing, it will sound much better. And yes, there are other ways to adjust the bias current, one of which is to adjust the plate voltage! I would assume that he doesnt; have a variac to mess with and he'll be tryign the old bread board technique with a handfull of resistors. I still say start with a 500ohm 10 watter, check the voltage drop across it to determine the total curent through the tube. If the tube is running less the 80% of it's rating (including screen current), I think you should just listen to it to determine how you like it. Where does one find a 15 watt rheostat at a reasonable price Scott? I'd like to have a couple at the shop for one of those abnormal amp experiments in terror I'm becoming famous for. Bruce |
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| peter Scott Bruce, |