Buzzin' Around

[MarkB]

I have a new push-pull 6v6 build that I'm battling with. Right now it's

6SJ7 -> Vol. pot -> 12AX7 -> tone stack -> PI

There's a buzz/hum that gets louder as I turn up the volume pot. With no guitar plugged in, it's not too loud. With a guitar plugged in, it's significantly louder. I assume that the problem is originating in the first preamp stage. I'm in the process of gradually making changes to the grounding to see if that's the problem. In any case, does it tell you anything that the buzz is there when no guitar is plugged in, and louder when one is?

[UR12]

Sounds like you have traced it down. The 6SJ7s data sheet states it can be run from AC or DC heaters. But I suspect you might be picking up hum from your AC heaters. You could try a few other 6SJ7s that may reduce or eliminate the hum but I think that you'll probably find some that are worse also. You could also try changing it to DC .

[Brian Hill]

I have a new push-pull 6v6 build that I'm battling with. Right now it's

6SJ7 -> Vol. pot -> 12AX7 -> tone stack -> PI

There's a buzz/hum that gets louder as I turn up the volume pot. With no guitar plugged in, it's not too loud. With a guitar plugged in, it's significantly louder. I assume that the problem is originating in the first preamp stage. I'm in the process of gradually making changes to the grounding to see if that's the problem. In any case, does it tell you anything that the buzz is there when no guitar is plugged in, and louder when one is?

Check for bad grounds on your pots.

Brian

[MarkB]

I have a new push-pull 6v6 build that I'm battling with. Right now it's

6SJ7 -> Vol. pot -> 12AX7 -> tone stack -> PI

There's a buzz/hum that gets louder as I turn up the volume pot. With no guitar plugged in, it's not too loud. With a guitar plugged in, it's significantly louder. I assume that the problem is originating in the first preamp stage. I'm in the process of gradually making changes to the grounding to see if that's the problem. In any case, does it tell you anything that the buzz is there when no guitar is plugged in, and louder when one is?

Check for bad grounds on your pots.

Brian

Will do. I'll probably reflow all the solder joints in the first stage.