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Dynaco-Doctor Forum Welcome! Need support, you got it. Or share your ideas and experiences. |
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Dynaco-Doctor Forum Welcome! Need support, you got it. Or share your ideas and experiences. |
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In Reply to: Is asymmetrical clipping normal for an ST-80? posted by wallewek on February 13, 2023 at 15:17:28:
I could swear someone responded to this and mentioned that the resistors R13 and R14 controlled bias on this amp, so I checked them and saw their values on all 4 were a bit high, running around 74 ohms instead of the nominal 68.
I adjusted them with 1K shunts -- all I had handy -- which brought them closer to the proper values. Testing, the clipping was closer to symmetrical. I'm going to quit while I'm ahead: the amp sounds pretty good as is, and output level is in the right ballpark.
In testing with a 400Hz sine wave into a dummy load, I noted that the power supply sagged a lot, and that impacted power. Presumable that's why there were upgrade kits with regulated power supplies. I'm not going to go there: I prefer tubes anyway, this was just a fix for someone else.
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- RE: Is asymmetrical clipping normal for an ST-80? - wallewek 15:32:16 02/17/23 (0)
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