Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Leandro on April 06, 2024, 03:55:33 pm
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Hi, everybody. I'm trying to build an amplifier that has channels 3 and 4 of the Diezel VH4 as a preamp (without the last cathode follower on the v4) and a power section/power supply that's very much like a Soldano SLO 50w, without the Presence and Depth controls.
The amplifier is pretty much complete, but I'm having a few problems getting it to work perfectly. As it is right now, I'm getting crosstalk between the two volume pots (they don't cut each other out, but you can hear that one pot is messing with the other, even though it's channel is not selected.
I'm using LDRs to switch channels, just like the SLO. I know, seems a bit archaic these days. I might change it in the future, but it would be nice to know if there's anything else that I've messed up before I start rewiring things.
Other than the volume pot interaction thing, I'm gettinga very strange, trebly kind of sound from the preamp. It almost sounds like the sound of an unplugged electric guitar layered with the amplifed sound. It's weird to try to describe sounds, but that's what comes to mind. This problem doesn't seem to show up if I plug the preamp into another power section via fx send. The signal from the FX send is, however very quiet. Into the 50w power section of another one of my tube amps, it sounds just slightly above bedroom level, even with the volume all the way up.
Since I got rid of the last gain stage on the original design of the VH4, I am wondering if that might be interfering with the FX loop.
Anyway, I'm posting the schematics over here, for the amp and it's power supply. I hope that helps. I could also post some pictures, if you guys think it might help. I'm new at this and by no means an amp builder, so any advice would be appreciated!