Resistor in place of Mid Pot

[RockinRocket]

What would the value resistor need to be to replace a 25k mid pot set to 10 on a typical Fender Marshall TMB stack.

As simple as this probably is.. is it 25k?

[tubeswell]

6k8 in most Fender BF TB tone stacks.

[martin manning]

What would the value resistor need to be to replace a 25k mid pot set to 10 on a typical Fender Marshall TMB stack.

As simple as this probably is.. is it 25k?

Exactly.

[Roe]

plexis used pots which read around 33k, although they were nominally 25k

[RockinRocket]

Great info. Ill be sure to compensate for the high measuring pots

[RJ Guitars]

http://duncanamps.com/tsc/index.html

If you have a curiosity about it, the Duncan amps tonestack calculator allows you to swap component values and see the resulting tone spectrum.

[RockinRocket]

So what would the resistor value need to be to simulate the Mid pot off or on 0? No resistor, just connect the bass pot and the other .022n to ground?

[tubeswell]

So what would the resistor value need to be to simulate the Mid pot off or on 0? No resistor, just connect the bass pot and the other .022n to ground?

yeah. Or you could put a 27k resistor in series with a 6k8 resistor, and put a shorting switch across the 27k resistor, to simulate a Fender T-B tonestack with the mid-scoop.

[RockinRocket]

How come I cant get a 6k8 response with a 25k pot by setting the pot lower. Duncons TS wouldn't let the frequency plot come anywhere near a 6k8 responce without replacing the pot with 6k8.

Because of this I question if a resistor in place of a pot would respond the same.

[tubeswell]

Maybe the sim-tone-stack can't really do real world stuff that well?

The 6k8 'tail' gives the mid-scoop alright, but it also depends how the treble and bass pots are dialled in (along with the rest of the values in the C-R network around the tonestack.

[pdf64]

How come I cant get a 6k8 response with a 25k pot by setting the pot lower. Duncons TS wouldn't let the frequency plot come anywhere near a 6k8 responce without replacing the pot with 6k8...

Which TSC template / model were you using, eg Fender BF, Vox, Marshall?
As with the mid control, the action of a variable resistor is different to a pot.

[martin manning]

So what would the resistor value need to be to simulate the Mid pot off or on 0? No resistor, just connect the bass pot and the other .022n to ground?

yeah. Or you could put a 27k resistor in series with a 6k8 resistor, and put a shorting switch across the 27k resistor, to simulate a Fender T-B tonestack with the mid-scoop.

No, 25k resistor from the bass pot to ground (as in the answer to your first question), and connect the 0.022u mid cap to ground. Fender and Marshall mid pot connections are different, and I believe RR is asking about a Marshall TS. A schematic is worth a thousand words...

[RockinRocket]

Great, I would have completely overlooked the grounding.

I was using Duncons TS with the Marshall plot for everything. I tried a 25k pot and a 6k8 for the fun of it. To my surprise using the same TS stack I couldn't match the curve of the other value with the Mid pot leaving every other value component untouched. I typically set the mids to 10 anyways and was interested in how to remove the pot to simulate a resistor on 10 if needed.

The experiment above left me confused a bit.

So what would the resistor value need to be to simulate the Mid pot off or on 0? No resistor, just connect the bass pot and the other .022n to ground?

yeah. Or you could put a 27k resistor in series with a 6k8 resistor, and put a shorting switch across the 27k resistor, to simulate a Fender T-B tonestack with the mid-scoop.

No, 25k resistor from the bass pot to ground (as in the answer to your first question), and connect the 0.022u mid cap to ground. Fender and Marshall mid pot connections are different, and I believe RR is asking about a Marshall TS. A schematic is worth a thousand words...

[tubeswell]

.. A schematic is worth a thousand words...

Indeed. My bad - sorry folks

[pdf64]

I suggest that the Fender template is used (with values adjusted as appropriate).
A single resistance for the mids can do everything that a pot can, whilst allowing greater range for the bass control.