Dual volume pot resistance value mod for coil split humbucker

Started by willio, April 18, 2021, 10:34:30 PM

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willio

I have been trying to tame a bright single coil split mode on my PAF-style humbucker.

I found the following diagram by user 'Alex C' on the Fractalaudio Forum

I wonder if that would do these jobs:

1. Coil split mode will see a 250k-ish vol pot value...
2. Retains 500k for humbucking mode.

The pickup sounds great on its own, on the brightside just like how PAFs usually are, but rather bright on the bridge for single coil, even with coil tap.

admin

Yes - that mod will alter the output Load impedance on the PU

But the down side is in the "250k" load mode, the volume taper will be a bit different than a stock Strat with stock 250K Audio Taper pot

The lower the Volume pot ohm value, the darker the tone will be
The higher the Volume pot ohm value, the Brighter the tone will be


Trivia - late 1960s Telecaster are very bright due to factory 1 meg Volume pot  = very bright tone
https://www.tdpri.com/threads/bakersfield-cbs-era-tele-wring-1-meg-volume-250k-tone.150243/

willio

Wow that was fast. Thanks!

I forgot my actual question, how do I translate this mod to a 50s Gibson wiring? Where should I wire the 470k resistor?

willio

Quote from: admin on April 18, 2021, 10:42:05 PM
But the down side is in the "250k" load mode, the volume taper will be a bit different than a stock Strat with stock 250K Audio Taper pot

Does it apply also to the default 500k unmodded pot, or only on the 250k modded?

mooncaine

Could a treble-bleed circuit be stuck in there to combat the darkening of sound as the volume's rolled down in "250k load" mode?

eUphonic

Quote from: willio on April 18, 2021, 10:50:18 PM
Wow that was fast. Thanks!

I forgot my actual question, how do I translate this mod to a 50s Gibson wiring? Where should I wire the 470k resistor?

I reply because I'm accustomed to guitar wiring and because I like trying to help but I'm not sure to understand the question: why 50 wiring would be a problem?

Wire each 4 conductors pickup to a push-pull splitting the coils, with the added 470k resistor if you want to... then go from the output of this push-pull to the external lug of each volume control. The rest of the wiring should follow the 50 wiring recipe without issues.

FOOTNOTE - resistive loads are constantly evoked as a way to tame an excessive brigthness while capacitance is never evoked... but a low value cap from split coil to ground would also tame the highrange... Try 470pF (picoFarad) in parallel or instead of the 470k resistor and you'll see what I mean. Increase or decrease the capacitance in the 220pF to 1000pF (=1nF) range if needed.
Used without added resistor, such a "stray capacitance helper" would have the benefit to keep the taper of the volume control(s) as it is, FWIW.
This recipe was shared by Seymour Duncan on his website, decades ago, BTW: it's a well known trick gone "under the radar" and not a delirium.

Good luck in your experiments. :-)

admin

Quote from: mooncaine on April 18, 2021, 11:20:21 PM
Could a treble-bleed circuit be stuck in there to combat the darkening of sound as the volume's rolled down in "250k load" mode?

sure, buts its all subject to taste

I like using a push-push Vol pot to kick treble bleed cap in/out - with 250k pot,  Start with 750pf treble bleed cap

admin

Quote from: willio on April 18, 2021, 10:53:42 PM
Does it apply also to the default 500k unmodded pot, or only on the 250k modded?
https://www.allaboutcircuits.com/tools/parallel-resistance-calculator/
only the 500k pot with 470k load resistor  = approx 242k

Quote from: willio on April 18, 2021, 10:50:18 PM
Wow that was fast. Thanks!

I forgot my actual question, how do I translate this mod to a 50s Gibson wiring? Where should I wire the 470k resistor?

use the same paf type humbuckers and same DPDT coil SPLIT SWITCH WITH 500K RESISTOR (470k are readily available) - then apply that circuit to standard LP control circuit  ( two 500k Vol, two 500k tone  - all audio taper)

in LP styp circuit - in coli split mode, when both Neck and Bridge pickups are "on" and in signle coil mode - you net a darker  121k load impedance 

willio

So, this is what I came up with based on the first diagram, would this work?

admin



Looks OK 0 but check your Tone pot wiring - one is reversed
- I prefer 0.022 uF tone caps for both Neck and Bridge - all subject to taste.


willio

Quote from: eUphonic on April 18, 2021, 11:28:57 PM
I reply because I'm accustomed to guitar wiring and because I like trying to help but I'm not sure to understand the question: why 50 wiring would be a problem?

Wire each 4 conductors pickup to a push-pull splitting the coils, with the added 470k resistor if you want to... then go from the output of this push-pull to the external lug of each volume control. The rest of the wiring should follow the 50 wiring recipe without issues.

FOOTNOTE - resistive loads are constantly evoked as a way to tame an excessive brigthness while capacitance is never evoked... but a low value cap from split coil to ground would also tame the highrange... Try 470pF (picoFarad) in parallel or instead of the 470k resistor and you'll see what I mean. Increase or decrease the capacitance in the 220pF to 1000pF (=1nF) range if needed.
Used without added resistor, such a "stray capacitance helper" would have the benefit to keep the taper of the volume control(s) as it is, FWIW.
This recipe was shared by Seymour Duncan on his website, decades ago, BTW: it's a well known trick gone "under the radar" and not a delirium.

Good luck in your experiments. :-)

Thanks. I'm a noob, and I'm trying to learn and experiment as I go. I have no training whatsoever except my blunt curiosity.

I'll give your capacitor suggestion a try, eventhough I have to do my homework as to how to wire it parallel to ground from my split coil lead. :-)

admin

Quote from: willio on April 18, 2021, 11:46:07 PM
Thanks. I'm a noob, and I'm trying to learn and experiment as I go. I have no training whatsoever except my blunt curiosity.

I'll give your capacitor suggestion a try, eventhough I have to do my homework as to how to wire it parallel to ground from my split coil lead. :-)

its a matter of what brand pickups are using?


eUphonic

Quote from: willio on April 18, 2021, 11:36:07 PM
So, this is what I came up with based on the first diagram, would this work?

Yes it should, although many players would pair the 15nF cap with the neck pickup and the 22nF cap with the bridge one.

EDIT - Ooops, our admin is right about the connection of the second tone pot, of course. My eyes are getting old...  ::)


Quote from: willio on April 18, 2021, 11:46:07 PM
Thanks. I'm a noob, and I'm trying to learn and experiment as I go. I have no training whatsoever except my blunt curiosity.

I'll give your capacitor suggestion a try, eventhough I have to do my homework as to how to wire it parallel to ground from my split coil lead. :-)

You're welcome. Always glad to help, although I hope not to create communicational "interferences" by adding my voice to your topic.
Regarding the location of a "high range softener" low value cap: it would be exactly where you put the 470k resistor or in parallel with it. :-)

willio

Quote from: eUphonic on April 18, 2021, 11:50:10 PM
Yes it should, although many players would pair the 15nF cap with the neck pickup and the 22nF cap with the bridge one.

How does it affect the tone? Would 22nF on the neck pickup help tame the highs?

eUphonic

Quote from: willio on April 19, 2021, 03:42:53 AM
How does it affect the tone? Would 22nF on the neck pickup help tame the highs?

The higher the capacitance of a tone cap, the most it darkens the tone of a pickup when the tone control is lowered.

Many players complain about muddy / boomy neck PU's in Gibson copies or guitar based on the Gibson recipe. Adding a dark tone control to a boomy / muddy pickup wouldn't make sense. Users solve this issue by mounting lower value tone caps for neck humbuckers (or P90's), giving a clearer sound to these PU's when their tone control is lowered. Hence 15nF instead of the usual 22nF in many tweaked LP's...

It's true that single coils are often paired with higher value tone caps (47nF, if not 100nF like in the oldest Strats)... But most of the related tonal differences appears to most users when the tone control is really lowered.

IOW, mounting a 47nF or 100nF instead of a 22nF wouldn't suffice alone to solve an excessive brightness when the tone control is @ 10/10 (if ever this idea was implicitely behind your question).

willio

Quote from: eUphonic on April 19, 2021, 06:09:39 AM
IOW, mounting a 47nF or 100nF instead of a 22nF wouldn't suffice alone to solve an excessive brightness when the tone control is @ 10/10 (if ever this idea was implicitely behind your question).

No, but it relates to what I will start with when I attempt a rewire. Currently, the guitar in question, though it sounds alright, it presents some symptoms of broken pots (push pull state being reversed), wrong wiring—out of phase between the two pickups of some sort (I really can't figure out what's wrong, cause resistence reading is single coil while it's in humbucking mode, and vice versa.)

So instead of troubleshooting it, I decided to do a rewire, and perhaps make the coil split more usable. It sounds great on the neck, but the bridge is much less to be desired.

I saw a post on the mylespaul forum about a PRS-style coil tap to get the inside vs outside coils (in series) when split, based on the 3-way position (bridge screw coil with neck slug coil when int rhythm pos, and bridge slug coil + neck screw coil in lead pos.) Would something like this work better?

eUphonic

Quote from: willio on April 19, 2021, 07:55:15 AM
No, but it relates to what I will start with when I attempt a rewire. Currently, the guitar in question, though it sounds alright, it presents some symptoms of broken pots (push pull state being reversed), wrong wiring—out of phase between the two pickups of some sort (I really can't figure out what's wrong, cause resistence reading is single coil while it's in humbucking mode, and vice versa.)

So instead of troubleshooting it, I decided to do a rewire, and perhaps make the coil split more usable. It sounds great on the neck, but the bridge is much less to be desired.

I saw a post on the mylespaul forum about a PRS-style coil tap to get the inside vs outside coils (in series) when split, based on the 3-way position (bridge screw coil with neck slug coil when int rhythm pos, and bridge slug coil + neck screw coil in lead pos.) Would something like this work better?

Better than what?  ???

I'm reluctant to express an opinion without knowing precisely what we're talking about: what is the guitar, what are its PU's? Because IME and IMHO, the success of any "alternative" wiring narrowly depends on the guitar with its components and on the goal of the user...

What I've noticed since I wire pickups is that coil splitting (or parallel wiring) generally requires powerful pickups to sound good: a generic P.A.F. clone will typically tend to sound too thin & bright in split mode, for example. That's where added resistors or caps can be useful.

Regarding the use of inner and outer coils in split mode, it's a useful trick, but once again, it's not a panacea IME/IMHO. It will sound good or not, depending on the guitar & PU's.

Anyway and without knowing what topic you're reffering to on MLP, I'll share this observation: a simple on/off/on switch can be used to select the inner and outer coils of two HB's in two different ways, with the series connection in center position. It's easy to wire and I'll share the related schematic on request.

With 2 push-pull pots, the same thing can surely be achieved, with one PP putting the coils junction to "hot" and the other PP putting the same coils junction to ground... but it would be less versatile than an ON/OFF/ON switch.

That's all I can say for the moment. :-)

admin

Quote
Regarding the use of inner and outer coils in split mode, it's a useful trick

And most apparent on the Bridge pickup.

The Jimmy Page Les Paul wiring remains a good reference
It's a bit like the Peavey T60

Install a phase reversal switch on Bridge pickup. Then when single coil mode is enabled, the phase reverse switch selects the active single coil in Bridge humbucker.

When Bridge PU Coil closest to Bridge is active, it's a brighter tone.

When Bridge PU Coil furthest away from bridge is active, it's more like a Clapton Strat Bridge+ Middle quack tone