This could be embarrasing...

[iknowjohnny]

....as maybe one of the more stupid questions ever asked here, but i really want to know. There is a ground reference in a guitar via the pot. usually 250k to 500k. most amps have a 1 M ground reference before anything else. Why the need for both? combined a 1M and a 250k in parallel are 200K. Why even have a resistor there in the amp? I'm thinking it has something to do with the volume on the guitar when turned down? (crossing my fingers i didn't miss something crazy obvious )

[paulster]

You could fairly likely be putting an effect before the amp with a capacitor-coupled output.

[Cliff Schecht]

The guitars output impedance is lower than the potentiometer resistance to ground. It's this resistance in parallel with the impedance of the pickups. This is a complex impedance mind you, not a simple resistive one. The point of the volume pot is to put a specific load on the pickups and actually acts as part of the tone shaping circuit of the guitar. That's why a guitar will sound different with different value pots. The 1 meg resistor on the amp input is meant to give you both a high impedance input (relative to anything that a guitar or pedal will look like, they should be low impedance outputs) and to give you a return current path for that tiny amount of current that the grid draws.

BTW, not a dumb question by any means .

[Andy Le Blanc]

The guitar controls used to be the only controls of the amp.
Some old control setups had the volume reversed so the amp would see a
constant impedance, most guitars now the pickup see the constant impedance.
You could use a grounded grid dress and get away with no controls.

The real point is that your actually impedance matching the pickup to the tube.
that's why the tone changes perceptively with volume adjustment.

put a LT fader in you guitar so both pickup and tube see a constant impedance,
and see what happens. Or....
try a variable resistance to ground instead of a volume control and see what happens.

[iknowjohnny]

Never even considered pedals ! (don't usually use them)