Can you parallel a grid-leak preamp with a cathode biased one?

[armstrom]

I'm considering building a bit of an odd-ball Tweed Deluxe style amp. My plan (at the moment) is to simply start with a standard 5C3 circuit but convert one of the preamp channels from grid-leak bias to cathode bias. I know by itself this isn't an issue but I also want to add a switch to run both channels in parallel from a single jack. Will this cause an issue? I would think so since the grid-leak biased channel would now see the 5M and 1M resistors to groud in parallel resulting in (rather than just the 5M) resuling in 833K to ground. Is this correct or am I totally missing something? I always hear about people running the inputs of a 5e3 in parallel with a Y cable, but I've never heard the same about a 5C3 (or earlier) amp.

[loudthud]

The input capacitor on the grid leak side isolates that grid from the cathode biased side. There shouldn't be a problem.

[armstrom]

The input capacitor on the grid leak side isolates that grid from the cathode biased side. There shouldn't be a problem.

Thanks for the reply! After I posted my question I took another look at the schematic and figured that was the purpose of the capacitor (otherwise the guitar pickup impedance would "mess-up" the bias in the same way) but thought I would wait for a reply.

Here's another quick one... Will the same grid leak resistor work for a 6SL7 as well? The stock circuit uses a 6SC7 but from what I have read online you can basically interchange them as long as you account for the different pinouts. Is there anything to be gained by playing with the grid leak resistor or is it a pretty rough adjustment either way? In other words, would 10M not sound much different than 5M?
-Matt

[loudthud]

My experiments indicate that the value of the resistor doesn't make much difference as far as bias point or plate voltage goes. It will make a difference with a crystal microphone or piezo guitar pickup however.