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Hi all - I'm having a problem with my ST70 where at higher volumes, say bass notes in dance music for instance, it is producing loud pops and crackles. Never happens at lower volumes, but it also didn't happen when I first built the amp. The pops correspond roughly with the energy in the bass notes at medium volume, and they really start going crazy if I crank it up even more. Worse in one side but somewhat present in both. Sounds sort of like a blown speaker but it's not.
I'm using the PC-3A driver board, PC-S7P power supply, and quad cap upgrade - so the amp is all new parts, not an original dynaco. It's about 10 years old.
I tried changing out all the tubes but it persists. Any theories would be appreciated since I'm a newbie at debugging things like this.
Andy
Follow Ups:
Did the amp have this problem before the changes were made? After the changes made did it happen right away? Recheck your solder connections.
I would check the tube sockets and tube pins for clean and the sockets for tight. I've had this problem and it was the contacts.
Thanks guys - yeah after posting this I isolated the problem to the right channel for sure. I'll redo the power tube socket soldering and some other soldering on the driver board to see if it helps. I also noticed that there's some damage on one of the caps on that side of the driver board so I'll replace that.
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