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HSH, one volume control, no tone: which pot value to use?

Ace Flibble

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As it says, building an HSH guitar with just one single volume control (I despise tone controls with a passion). Just to make things extra complicated the neck pickup is going to be a P-Rails, so we've got HSH, HSS and HSP to balance out and the guitar uses a Gibson style 3-way toggle switch, not a Strat style switch, so there can be no Esquire-style extra capacitor shenanigans either. Oh yeah, and it needs to be a push-pull or push-push (figured I'd throw in my beloved phase switching as well), so I can't split the difference and use 300k or concentric pots, nor do I have the tools to modify any P/P pots. So 500k and 250k are my only options. Fun.

Ultimately, the kind of tone I like is a bridge pickup with two 500k controls with a 0.015uf capacitor on the tone control and for single coils and P-90s, one 250k pot and one 500k pot with a 0.033uf cap. I always leave the tone controls at 10 though and then get royally pissed off if they ever get nudged down so invariably I end up ripping them out and put together guitars with only the one volume control. Never done one volume with such a mix of pickups before though.

I always thought that one 250k pot will result in the same tone, when at 10, as a 500k volume and a 500k tone pot both at 10. However, I've since been told that this is wrong and that the single 250k pot will always sound slightly darker. Which is correct, or is neither correct?

Or, perhaps more simply, could I use a 500k pot then add extra 500k resistors to the neck and middle pickups in a way that somehow does not effect the bridge pickup?

Or, considering even this one control is always going to be left full on, is there even any need to worry? At 10, do the different values of volume pots even matter?
 
500k pots are indeed hotter/brighter than 250ks.
As a volume control, there is a resistance placed parallel to the signal, which is 0 to 250k Ohms on a 250k pot, depending on the position, and 0 to 500k Ohms on a 500k pot, depending on the position. A lower resistance at the maximum settings will translate to a lower resonant frequency.
As a tone control, a 500k pot functions identically to a 250k pot from 0 to 250k Ohms, and beyond that, further removes the capacitor from the circuit, resulting in less of your high frequency content being sent to ground.

Depending on your output impedance, the difference between 250k and 500k pots should be subtle to begin with. I think people put WAY too much thought into pot values.
Just pick one and it will sound fine. If you don't like it, change the pots. They only cost a couple of bucks and take a few minutes to swap around.

As far as decreasing the parallel resistance on the neck and middle pickups only, it doesn't work that way. Resistance parallel to the output is parallel to the entire signal. The only way to have a lower resistance against one pickup that does not apply to the other pickups when multiple pickups are being played is to isolate the pickups by placing a series resistance between them. This, of course, is equivalent to running through another volume pot. It will decrease the output and treble.
 
Ah-ha, think I have a slightly firmer grasp on it now, thanks for the info.

When you say "placing a series resistance between them", am I right in in assuming this pretty much means putting a resistor on the pickups' hot output before the selector/control pot?

Though from the sound of it I should pretty much just go for 250k and worst comes to the worst, switch to 500k.
 
Ace Flibble said:
Ah-ha, think I have a slightly firmer grasp on it now, thanks for the info.

When you say "placing a series resistance between them", am I right in in assuming this pretty much means putting a resistor on the pickups' hot output before the selector/control pot?

Though from the sound of it I should pretty much just go for 250k and worst comes to the worst, switch to 500k.

Yes, it would mean placing a resistance between the neck/middle pickup and the output.
This would increase the impedance of the load parallel to the bridge pickup, but also decrease the output of the neck/middle pickup.
 
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