"knocking Down" Pot Value (taper?)

[Talman_Hawk]

I was thinking of trying John Spina's idea for changing a volume pot to a lower value with a parallel fixed resistor (described at "Tweaking either a 1 meg pot to a 500k and a 500k to 250k"). But Lovekraft mentioned in the thread about cap values that doing so would "screw up the taper" of the pot.

Is there any reasonable way of "knocking down" a 1 Meg pot to 300K or so without it becoming a really dumb idea? I was hoping to get a little different tone out of a 13.8K bridge humbucker when it's being cut to a singlecoil, with a 453K resistor on a 1 Meg push/pull pot. I'll pass up that plan if there's no real return for the effort.

Thanks.

--

Doug C.

[JoeAArthur]

I was thinking of trying John Spina's idea for changing a volume pot to a lower value with a parallel fixed resistor (described at "Tweaking either a 1 meg pot to a 500k and a 500k to 250k"). But Lovekraft mentioned in the thread about cap values that doing so would "screw up the taper" of the pot.

Is there any reasonable way of "knocking down" a 1 Meg pot to 300K or so without it becoming a really dumb idea? I was hoping to get a little different tone out of a 13.8K bridge humbucker when it's being cut to a singlecoil, with a 453K resistor on a 1 Meg push/pull pot. I'll pass up that plan if there's no real return for the effort.

Thanks.

--

Doug C.

You can tweak the values of your pots all you want with resistors. Sure... it might change the perceived "taper" of the pot. But that only comes into play if you actually turn the pot down from 10. If you don't... then you won't notice or care.

What are you trying to achieve? If you like the sound with the additional resistor added in, then it will be worth it. No one can answer the question if you will like the difference or not.

Personally, I don't care that much about pot values in my guitar. If I want less treble I'll turn it down on the amp - and if I want more then I will turn it up. If you want to be able to control the response of the sound outside of the amp - then an equalizer pedal would be more flexible - than switching pot values while you are switching coils.

There really isn't that much difference between pot values in the guitar - although I'm sure that some will argue.

[Talman_Hawk]

You can tweak the values of your pots all you want with resistors. Sure... it might change the perceived "taper" of the pot. But that only comes into play if you actually turn the pot down from 10. If you don't... then you won't notice or care.

Um, yeah; strange as it may seem, I actually use the volume comtrol to, well, control the volume of the guitar. Besides, I'm planning to put some of those DiMarzio knobs that "go to 11" on it, so that changes the whole equation.

What are you trying to achieve?

Maybe I wasn't clear enough about what I had in mind. Based on the premise that singlecoils "like" 250K pots, and humbuckers are generally controlled with 500K pots, it seemed like a good idea to be able to change the value of a pot when the pickup it controls is "cut," i.e., acting as a singlecoil. Maybe it's just one of those ideas that only works in theory. Maybe "half" of a 13.8K humbucker will be alright when it's "looking at" a 1 Megohm pot.

If you like the sound with the additional resistor added in, then it will be worth it. No one can answer the question if you will like the difference or not.

Okay, but the question wasn't so much about liking the difference, it was about a practical way to get around screwing up the taper of the volume pot. (Y'kmow, all that "audio vs. linear" stuff?)

There really isn't that much difference between pot values in the guitar - although I'm sure that some will argue.

Yep, some will, myself included.

I was looking more for technical information than opinion, but thanks for "bumping" the topic up the list a little, anyway.

Maybe now Lovekraft or somebody can get a look at it, and tell me if this is another of those great ideas that just won't "fly," or if there's a practical way to do it

[mikhailgtrski]

I'm hoping to do the same thing, changing the pot value when the coils are split.

I drew up a schematic in this thread vintage voicing... haven't tried it yet. I have the resistor in series with the pot - it should probably be wired in parallel and with a different value, like the tutorial shows, so back to the drawing board .

EDIT: here's a revised schematic - untested, but I think it'll do the trick:

UP = inside coils w/ 250K volume

CENTER = humbuckers w/ 500K volume

DOWN = outside coils w/ 250K volume

Mike

Edited March 21, 2006 by mikhailgtrski

[JoeAArthur]

Technically speaking, there is no "correct" value of volume control for single coil or humbucking pickups. There is tradition... but that's not the same thing as "technically correct".

And also technically speaking... most people including me simply turn the volume control up or down until the volume is correct - regardless of taper.

However, if you want to maintain volume control taper as close as possible and switch the total value of the pot at the same time...

We'll assume an audio taper.

Turn the pot to halfway and measure the difference between the center terminal and both outer terminals in turn. Note: the pot must be disconnected in order to do this otherwise you may be measuring other components in parallel.

On an audio pot, one measurement (the center lug to ground) will be roughly 10-25% of the total value of the pot... like 50K with a 500K pot.

So... how to convert a 500K audio taper pot to a 250K audio taper pot.

The closest you can get is to bridge the pot with TWO resistors. One from the hot lug to the center lug, and the other resistor from the center lug to ground. Get as close to a standard resistor value as the measured value. For a 500K, this will probably be a 470K to the center terminal from the hot terminal and a 47K from the center terminal to ground. (remember pots are probably 20% tolerance).

To make this switchable will take two poles. You'll also need one other pole to do the coil tap on a single pickup. Another three poles for the other pickup/volume control.

Placing a 500K resistor across the 500K pot as per mikhailgtrski's diagram is a much simpler approach than trying to maintain pot taper.

[mikhailgtrski]

And also technically speaking... most people including me simply turn the volume control up or down until the volume is correct - regardless of taper.

+1

It's probably not worth the hassle & complexity. And having a slightly more gradual taper could actually be beneficial, depending on how you use your volume pot.

[Talman_Hawk]

Okay, that's some very good info.

Thanks, guys!

[lovekraft]

Pot taper probably isn't an issue for most of us - however, for us old-timers that do volume swells with the guitar's pot, it's pretty critical. My advice would be to try mikhailgtrski's setup, and if it doesn't interfere with anything else you do, you've found a solution. Even using two resistors won't preserve the original taper (although it will be closer), so unless you're willing to use a dual-ganged pot with different elements in each half, and switch both hot and ground, you're going to have to find a compromise that works for you.

[mikhailgtrski]

however, for us old-timers that do volume swells with the guitar's pot, it's pretty critical.

Well, I'm one of those old-time volume swellers

Correct me if I'm wrong (and I haven't tried this circuit yet), but it seems to me that the resistor won't affect the taper when it's out of the circuit (humbucking mode). If that's the case, it's a non-issue for me, since I only do swells with the humbuckers.

Mike

[scott from _actual time_]

UP = inside coils w/ 250K volume

CENTER = humbuckers w/ 500K volume

DOWN = outside coils w/ 250K volume

this is a really neat idea, and a clever switching scheme, but in practice i think the lower pot resistance for the split humbuckers might actually make them sound less like single coils.

most single coils are 7-9 kohms, but medium output humbuckers run 12-14 kohms. that's the main reason that most split humbuckers don't sound like a real single coil. so if you're going to split a medium output humbucker, you might not want the 250k pot resistance bleeding off more of the signal, since the 6-7 kohm humbucker coil is already lower output than most single coils.

high output humbuckers, ranging from 16-18 kohms and higher, sound more like real single coils when split. in that case, the lower pot resistance might smooth them out nicely. i run high output humbuckers, but i like raw tones from my split coils, and the higher resistance pots work fine for that.

[mikhailgtrski]

Good point...

I'm using PAF-type humbuckers (8.13 kohm) in my current rig with a 500k pot (no parallel resistor scheme) and they are a bit on the --overly-- bright side when split. But that guitar tends to be on the bright side anyway. It might be a different story with the new one... of course, the resistor value can always be tweaked if necessary.