chicago_mike wrote:...Something that shows a simple channel switch idea...
Well it depends on the circuit you're working on..
I mean, does it share any preamp stage or tone stage between channels?
On a guitar tube preamp I built years ago, I used reed relays bypassing (or not bypassing) triodes in series and selecting tonestacks.
They're quite noiseless and affordable. You can use any relay bypass circuit you find here around.
I also modified several Soldano's SP77 to solve their "channel bleeding" opto's issue...