Tube Amp Archive

Yes I believe it is exactly a PS1, and sounds as such. Very nice. Cool amps, will probably be more collectible in the future.

KT88's installed. Pin 1 on the KT88 had no connection. Amp biased for 70% dissipation, ended up needing -33V bias voltage. So in the end the mod was unnecessary, however it will ensure future KT88's can be biased properly for future owner. @toddgw, good advice. Coupling caps test OK. They are Orange...

Yes, will adjust R80 if needed for correct bias. Looking at the datasheet for JJ KT88 I've purchased, it looks like Pin 1 is G3. So I should tie pin 1 and 8 together, correct? Right now Pin 1 on the socket is not wired to anything. https://www.thetubestore.com/lib/thetubestore/JJ-KT88.pdf Edit: On t...

Martin, thank you for the schematic. That was what I was thinking and you made it too easy for me. I've revised the amp to that circuit, except I kept the stock 22k resistor and stock electrolytic value (changed to 47uf 160V). Bias voltage now ranges from -37 to -68V. I have ordered a set of KT88's ...

Thank you Sluckey. I could add a simple Voltage Double if need be, I think. Seems like others have done that for bias supply with no issues.

Or is there a better option?

Looking like KT88's are my answer. Would love to get another opinion.

Anything that needs to be done besides swap tubes and rebias?

Amplifier is an SG Systems 2x12. From the previous owner, it is running Sovtek 5881/6L6WGC at 580 plate volts! Data sheet for this tube specifies max 250V. Who knows how long it's been like this. The amp actually seems to running fine, sounds decent. Screen Voltage is 290V. Bias supply is 25V. Origi...