Tube Amp Archive

Well, I think I got this one wrapped up. Turned out the hum was mostly from a lead dress issue on the reverb channel, on the input from the volume wiper to the preamp. Changing the lead dressing while the amp was running to minimize hum worked, but still wasn't perfect. Found I had more hum when bac...

You're right to put the preamp filters back to 20uF, but don't bee too quick to go back to the 70uFs in the main filter. Parralleled, that gives you only 35uF (less than in a Deluxe Reverb) which is not enough to surpress 120Hz hum at volume. 220s may be a bit too "tight." You might try 100uF (givi...

Working on a 1967 Twin Reverb for a friend, he complained of too much hum. I found that someone messed around with this amp before--replaced a lot of resistors and some caps ('80s vintage filter caps). Lots of non-factory stuff that is going back to original. 220mfd and 80mfd filters going back to 7...