Probably a silly mix resistor question...

[EFK]

I'm working on a cathode bias 2-KT66 amp which is *kind of* like a JTM45, aside from the cathode bias. The preamp circuit is a little different, mostly same values but I wanted to do it all w/ a single triode so the tone stack is plate driven as opposed to cathode follower. PI is the same. However, I like it very simple and here is the stupid question: I'm using only one input, and single channel only, so is there any issue w/ leaving the 270K mix resistor out of the signal path? Of course each channel whether high or low input on a JTM has the resistor in the path, but as far as I can tell with only a single channel there is no *need* for one to be there. There is no mixing, after all. So, is the absence of this resistor going to have some kind of effect down the line through the PI?

Thanks for humoring what seems self-evident.

[pdf64]

A resistor there can help to reduce blocking distortion at high volume settings. Also, if fitted on the tube socket, resistors there act as grid stoppers, thereby increasing immunity from oscillation.
But if circuit minimalism is desireable, then you could go straight from vol control wiper to grid. Maybe mitigate for loss of grid stopping by using screened cable.

[EFK]

Aaahh! I see what you're saying - I didn't think of it that way. I've just looked at them as keeping the two channels somewhat isolated from each other, but now I see it along the same lines as the resistor/s off the inputs into the first stage. In that case, given there are no 'channels' to isolate, need it be as high as the typical 270K/470K? Wondering if any tonal effect will be evident, say 'typical' 270K vs. 100K or 68K? Any thoughts? Thanks!

[pdf64]

10k to 47k would be ample as a grid stopper, but to be effective against blocking distortion, I'd go for something >= 220k.
It's worth trying the 'nothing' solution first - you may not have a parasetics or blocking distortion problem to solve.