CurtZHP
Well-known member
Built a tube instrument preamp a while back, using a similar topography to most tube guitar amps out there. Both halves of a 12ax7 with a gain pot between them, with a final stage built around a 12au7.
The original power supply put out around 250VDC. The new supply is sending around 300VDC. Now it seems like it overdrives much more readily. Got out the scope and the tone generator and ran a sine wave through it. First stage seems fine. Second stage starts to clip as the gain pot is turned up all the way, as one might expect. But the whole thing seems to distort quite readily.
I guess this was to be expected, but I'm unsure as to the most effective way to deal with it. Changing plate resistors? Cathode resistors? Changing the power supply again to reduce the output voltage?
(The new power supply is a simpler design compared to what I had earlier. Got it from a Youtuber who goes by the handle of "Uncle Doug" and has a ton of videos about guitar amp tube circuits.)
The original power supply put out around 250VDC. The new supply is sending around 300VDC. Now it seems like it overdrives much more readily. Got out the scope and the tone generator and ran a sine wave through it. First stage seems fine. Second stage starts to clip as the gain pot is turned up all the way, as one might expect. But the whole thing seems to distort quite readily.
I guess this was to be expected, but I'm unsure as to the most effective way to deal with it. Changing plate resistors? Cathode resistors? Changing the power supply again to reduce the output voltage?
(The new power supply is a simpler design compared to what I had earlier. Got it from a Youtuber who goes by the handle of "Uncle Doug" and has a ton of videos about guitar amp tube circuits.)