Least intrusive master volume for princtone reverb

[uneumann]

I tried replacing the grid leak with a 1MA pot as discussed, and the taper was not usable. It goes to full volume at something like "1" out of "10". I checked the pot and made sure it wasn't wired backwards (with reverse taper) or defective. I'm wondering if I really understood the instructions. Here, again, is a picture of the circuit:
[ATTACH=CONFIG]28353[/ATTACH]

Is this right?

Is there a reason you're not tying the bottom of the pot to ground (instead of R40)?
You might try that instead.

Since R40 is not bypassed, it's the major part of the cathode output resistor. So your pot is trying to control the voltage between grid and cathode while the tube is doing it's best to make sure there is no difference between grid and cathode. Maybe I'm missing something, but I'd just try connecting the bottom of the pot to ground (ideally at the ground end of R40).

[Enzo]

I think you are missing that R40 is half of the load in this split load phase inverter stage. So that grid is floating somewhere like 200v to ground. Most volume controls are across the grid to cathode ground. R41 is the bias for the tube, so his volume is across it. If you took the pot to ground, you would then either have 200v across the pot or at least we'd be grounding the grid.

Now is it a good way to go about it? I don;t know, but I understand why they did what they did.

If it were mine, I'd probably add a cap and a resistor. I'd drag the low end of the pot to ground, and add a cap at its wiper to block DC from the PI. Then I;d add a 1m resistor from the grid to the top of R40 as a grid return.

[elipsey]

I think you are missing that R40 is half of the load in this split load phase inverter stage. So that grid is floating somewhere like 200v to ground. Most volume controls are across the grid to cathode ground. R41 is the bias for the tube, so his volume is across it. If you took the pot to ground, you would then either have 200v across the pot or at least we'd be grounding the grid.

Now is it a good way to go about it? I don;t know, but I understand why they did what they did.

If it were mine, I'd probably add a cap and a resistor. I'd drag the low end of the pot to ground, and add a cap at its wiper to block DC from the PI. Then I;d add a 1m resistor from the grid to the top of R40 as a grid return.

fwiw, this is what i ended up doing. i also added a grid resistor to the pi. sounds pretty good, actually pretty badass at higher gain settings, imo. it's almost a little surprising...

[g1]

Can you post a schematic for your final iteration?

[elipsey]

Can you post a schematic for your final iteration?

I ended up with a regular volume control between the last gain stage and the PI. Pretty much what you'd expect, plus a grid stopper for the PI input:


For my taste this sounds much better than when I tried placing a MV after a concertina PI. Maybe the grid stop resistor would have helped with that as well. Actually, I think it may have sounded a little better still with the pot replacing that 1M bias resistor, although I'm not sure why that would sound different than what I have now.