| Author | Message | ||
     Don Cowie |
My MM 65 2X10 started hissing badly one day I put the gain (volume) up to 8. Since then It has not stopped. The hiss sounds worse the more treble that is added, although the amp seems to be working fine. I have obviously changed the 2 EL34's and 7025 tube to no avail. This is driving me insane. Has anyone ever come up against this problem before. I had an amatuer electronics guy look at it and he cannot isolate the problem. he says the noise is across the whole circuit. Please help if you can as I love this amp. | ||
| michael kaus |
You could have just a noisy op amp in the preamp. You will have to trace it back with a scope to find out where it starts. Does it happen on both channels or just one? If both channels, it's after the preamp stages and would make it easier to find. I think(don't have schematic here in front of me) that the op amps are the same from one channel to the next so if it only does it on one channel, you can a least rob the amp out of the unused channel to get the one working that you use. If both channels do it, look at the buffer after the two channels and start there. Come to think of it, you might try cleaning the sockets on the PI tube and see if that helps. I had one that made a strange hissing noise that was coming from the driver tube socket-still don't really know why, but it was. Re-tension as you do it. I really vote for noisy op-amp though. Mike. |