AthenaZephyrian
100+ Head-Fier
Not sure where else to post this, but my SRM-1 Mk2 Pro has developed an infernal left-channel hum/buzz (sounds like a very quiet 60hz sawtooth wave) that is dependent on position of the volume potentiometer. I Thought it was a problem with a filter cap at first (electrolytic, installed a few years ago when I recapped the amp), but the buzz persists. There's no visible sign of capacitor failure (no bulge, no leakage). I don't have a capacitance measuring device, so I'm not able to check that the caps are still within tolerances of their original rating. I did check the caps with an ohm meter and they seem functional, but I cannot, obviously, tell anything other than that they have not entirely failed.
I'm gonna try cleaning the pot with some deoxit (had to order it, on its way; I have another amp that definitely needs it anyway) but I seriously doubt that the pot is the issue.
Now, the transformer does hum (very quietly) at exactly the same frequency and with a similar timbre (sawtooth-ish). I suppose there could be some inductance (from the coils, perhaps, moving slightly relative to the magnetic core) that makes it into the audio signal, but I haven't found evidence that anyone else has experienced that phenomenon. What I have found is a lot of people talking about DC offset in the wall AC. Now, if I understand those posts correctly, the resultant sound from DC offset is emitted by the transformer, and does not audibly infiltrate the audio path. That said, maybe this is the issue; perhaps it actually can end up in the audio output of the amplifier.
Maybe it's the filter caps and I need to recap it again (and possibly figure out what other aging components caused a cap failure, if indeed there is one)? Maybe it's the transformer (bleh I don't wanna replace an HV transformer)?
This is absolutely driving me up a wall. If anyone has suggestions, I'm all ears (haha).
I'm gonna try cleaning the pot with some deoxit (had to order it, on its way; I have another amp that definitely needs it anyway) but I seriously doubt that the pot is the issue.
Now, the transformer does hum (very quietly) at exactly the same frequency and with a similar timbre (sawtooth-ish). I suppose there could be some inductance (from the coils, perhaps, moving slightly relative to the magnetic core) that makes it into the audio signal, but I haven't found evidence that anyone else has experienced that phenomenon. What I have found is a lot of people talking about DC offset in the wall AC. Now, if I understand those posts correctly, the resultant sound from DC offset is emitted by the transformer, and does not audibly infiltrate the audio path. That said, maybe this is the issue; perhaps it actually can end up in the audio output of the amplifier.
Maybe it's the filter caps and I need to recap it again (and possibly figure out what other aging components caused a cap failure, if indeed there is one)? Maybe it's the transformer (bleh I don't wanna replace an HV transformer)?
This is absolutely driving me up a wall. If anyone has suggestions, I'm all ears (haha).
