Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: JustMike on January 25, 2021, 05:27:24 am

Title: Channel switching 2204?
Post by: JustMike on January 25, 2021, 05:27:24 am

I built a hot rodded 2204 out of an old Peavey VT series chassis & iron. It sounds good but it hisses at high gain settings- i guess that's just the nature of the beast. Anyway, I have an extra 9 pin socket and i want to add a clean channel. I believe i will have to have a relay right off of the input jack, a seperate tone stack and another relay going into the PI. I think this can be done with the one tube. Is there a schematic out there i can reference?
Thanks!

Title: Re: Channel switching 2204?
Post by: SnickSound on January 25, 2021, 06:18:41 am

Yes a single tube is enough for a Blackface clean channel: plate fed tonestack into recovery stage into pre PI relay.

You can connect the input to both grids at the same time, use the 2nd half of the relay to mute the dirty channel (ground the grid of the 2nd stage) when in clean mode instead. This is less likely to pop.

There is a little more to it (e.g. make sure the pre PI cap always has a path to ground, probably want a voltage divider after the clean recovery stage so it doesn't jump to full volume too fast, etc) but that's the gist of it.