Yeah weird that your reply showed up before my post. Hope the malware isn't digging deeper into the server lol.
Anyway that's exactly what I'm thinking. An EL34 should drop in there just fine with maybe a change in cathode resistor. Will be interesting to see how that affects the noise issue. Unfortunately all my spare tubes are sitting in storage in another state after a move. So I will have to wait until after next weekend when I go to get the rest of my stuff to try that.
Further work on my KT120 DLM (with pics)
Moderators: pompeiisneaks, Colossal
Re: Further work on my KT120 DLM (with pics)
Friend loaned me a JJ EL34. So the amp is up and running again at least. But man that noise just drives me nuts. I think its worse now with the EL34 installed. Probably just something to do with the frequency response. That or I just haven't played it in a while and gotten used to listening to clips I eq'd the noise out of.
Anyway I'm back to thinking it's parasitic oscillation, that's the only thing that I can think of. Maybe I'll try some NOS 12ax7's and see if the lower gain helps. Other than that I'll probably start increasing grid stoppers and see if I can't at least make an impact on it.
Does anyone see any issues with the board layout that could be causing problems? Its a bit different from how Ken did his preamps and the idea that its causing problems has been floating in the back of my mind for a while hoping that's not the case.
Anyway I'm back to thinking it's parasitic oscillation, that's the only thing that I can think of. Maybe I'll try some NOS 12ax7's and see if the lower gain helps. Other than that I'll probably start increasing grid stoppers and see if I can't at least make an impact on it.
Does anyone see any issues with the board layout that could be causing problems? Its a bit different from how Ken did his preamps and the idea that its causing problems has been floating in the back of my mind for a while hoping that's not the case.