Winters
Active Member
I am currently repairing a Revox Model 40 amp, made in Switzerland in the early 1960s. I have figured out most of the problems with the power amp section (see thread: http://www.audiokarma.org/forums/showthread.php?t=620580 ) and I got it to work nicely using line inputs - good sound, absolutely no hum whatsoever.
On the other hand, I have a problem with the phono section. It works and produces sound in both channels but there is a slight AC hum present that varies with the volume. It does not overpower the music but there is too much of it for a hi-fi amp.
I checked basic ground connections (phono rca inputs/mode switch/first preamp tube) and I see no faults there. Tried different turntables with different cartridges - nothing really changes.
I would be grateful if someone had an idea concerning this hum.
On the other hand, I have a problem with the phono section. It works and produces sound in both channels but there is a slight AC hum present that varies with the volume. It does not overpower the music but there is too much of it for a hi-fi amp.
I checked basic ground connections (phono rca inputs/mode switch/first preamp tube) and I see no faults there. Tried different turntables with different cartridges - nothing really changes.
I would be grateful if someone had an idea concerning this hum.