One Humbucker, One Volume Pot Cavity - What Wiring Options?

BillDL · February 2022

In October 2021 @HarrySeven gave a list of own-brand "Fazley" electric guitars from Bax Music based in the Netherlands that he believed might make good modding platforms. That was followed up by him in January this year, having just received the surf green Fazley Hot Rod FTD182SG-M he had ordered. I bought mine a few weeks before HarrySeven provided the list of potential modding guitars. I paid £69 for mine which WAS NOT described as B-Stock, even though the RRP was purportedly around £130 at the time.

The guitar is a Strat shape with very chunky maple neck, linden/basswood body, hard-tail top loader strat style bridge, 1 x generic 2-wire humbucker (presumably ceramic) in the bridge position in a plastic mounting ring, and 1 x small can volume pot in a cavity probably only big enough for a full sized pot but deep enough for a push-pull pot.

I've done a bit of work to this guitar converting it to a through-body strung bridge, replaced the nut which looked to have been the wrong string spacing, levelled and dressed the frets, and fitted better tuners. It played really well once I had finished my tinkering and I enjoy the simplicity for a change. The volume pot does lose highs when rolled off, but that would actually be a good thing if the pot had a consistent taper.

It's now without strings and I've removed the pickup and pot while I consider what to do with it. I have two spare bridge position "zebra-coil" humbuckers both with 4 conductors that allow coil splitting: (1) Alnico V 16.4 kOhm (2) Alnico II 8.5 kOhm. I also have various pots including a 500kOhm Push-Push one. I don't really want to start drilling holes and adding mini toggle switches, because that defeats the whole point of having a simplified guitar, but I was wondering how best to get a few different sounds from it with a single push-push pot or perhaps even a "blend" pot that I could buy.

1. Simple coil split using push-push pot with expected drop in volume and thinner sound.

2. Push-Push partial coil split using a resistor on the switch between the split coil's signal (that would normally go straight to ground) and ground. This method retains more strength in the remaining single coil than what there would normally be, i.e. a less thin coil split sound. In other words, instead of the remaining coil of the 8.5K pickup now being 4.2K it might be 6K depending on resistor value.

3. Bridge one of the the push-push switch's contacts to a leg of the volume pot so that when it is engaged it does a "gradual" coil splitting using the volume pot.

4. Instead of coil-splitting, use the push-push switch to flip the coils between parallel and series, resulting in a "wider" and "thicker" parallel single coil sound as well as having full humbucker series mode available.

5. Buy a dual concentric pot and add tone control.

This guitar isn't a shred machine and I'm not a shredder. I want it to be a straightforward uncomplicated blues rock guitar but with an optional variation in pickup sound if needed. I would be keen to hear what option you might choose to wire it up with.

PrecisionGuided · February 2022

IMO option 5. A tone pot is more useful than coil split.

TTony · February 2022

Depends on how/where you play - using a push/push as a blower switch might be useful in a live environment, gives you full-on output for solos etc, and the rest of the time the output is moderated via the vol pot?

But then I suppose you could just use a pedal for the same result!

Funkfingers · February 2022

Option 2 - partial splittage.

I agree that a fully variable tone control is desirable but stacked knobs can be a faff to use, defeating the object of simplicity.

ICBM · February 2022

2 or 4.

I'm not normally a huge fan of parallel-wiring a humbucker in a guitar - to me, it usually sounds thinner and a bit indistinct rather than 'wider' or 'thicker' than a single coil - but in a Strat-type guitar bridge position it can have a bit of the flavour of the Strat bridge/middle sound, so might be quite useful. And is hum cancelling, unlike even a partial split.

(Parallel wiring a humbucker in a bass sounds great, I don't know why it's so different!)

BillDL · February 2022

Thank you for your insights guys. Still undecided.

andy_k · February 2022

Coil split, or flip phase for a thinner tone. Push/push pot to make it better.
Or there is a circuit that I have used which creates a tone pot when selected, which gives you an on board wah wah.
Most switching options with a single humbucker are pretty underwhelming, but it does depend on the pickup.
Personally, I'd go coil split, but you will have a noisier selection, which gets ridiculous with a lot of gain, also, switching pots are not the best performing pots, you get what you pay for. Sometimes its a lot, for not very good performance as a volume pot.

Dave_Mc · February 2022

Obviously this depends on how much you want different tones out of the one pickup, but I usually use the single volume knob on a guitar-with-no-tone-pot to switch a treble bleed in and out (granted, those are guitars with multiple pickups, not just the one, so there are more tonal options available). My reasoning being that (a) I hate how the volume knob sounds turned down without a treble bleed cap for cleanish tones but also (b) I don't like having no ability to tame the extra treble you get with no tone pot and having the treble bleed on a switch sort of gives you the best of both worlds (plus I actually do like how the volume sounds without a treble bleed for lower gain overdriven tones).

Might be worth considering. Unless you know you hate treble bleeds, of course, in which case it's pointless.

ICBM · February 2022

andy_k said:

Coil split, or flip phase for a thinner tone. Push/push pot to make it better.

Reversing phase *within* a humbucker sounds terrible. The coils are so close together that the harmonic cancellation is almost total. It's also not hum-cancelling, and the hum can be louder than the signal...

andy_k said:

also, switching pots are not the best performing pots, you get what you pay for. Sometimes its a lot, for not very good performance as a volume pot.

That used to be true, but there are now plenty which are as good as standard pots. I have a couple of Bourns push-push ones in my PRS, and they have very nice tapers for both volume and tone.

BillDL · February 2022

I fully agree about switching phase with the two coils of one humbucker. I didn't like the results at all.

I think what I'm going to do is assemble the guitar and leave the pickup wires dangling out the pot cavity (it's a long cable). I have a bunch of thin insulated wires with mini crocodile clips at either end that I can use as jumper cables to test out some variations with the push-push pot. I might succumb to temptation and drill a cavity for a mini 2 or 3 position toggle switch.

I'll report back when I get around to it, but I'm in no particular rush.

Dave_Mc · February 2022

ICBM said:
That used to be true, but there are now plenty which are as good as standard pots. I have a couple of Bourns push-push ones in my PRS, and they have very nice tapers for both volume and tone.

I got a couple of Bourns push-push pots, which were pretty nice... but the taper was really weird. It said something like "D" on them, which I think is some kind of log taper, but it seemed to me more like linear (maybe even worse). Not much happened until the knob was nearly at 0, and then everything happened all at once. I think I made the mistake of buying them from CPC/Farnell, though they were called guitar pots...

BillDL · February 2022

I'll make sure to check that aspect out @Dave_Mc

The switched pot I dug out of my spares boxes yesterday is an Alpha branded (Korea) 500 kOhm one with Audio/Logarithmic taper. See PTSW03 here:

https://www.axetec.co.uk/guitar_parts_uk_053.htm

I bought that a few years ago. The two that I bought more recently are no-brand ones but look exactly the same.

Dave_Mc · February 2022

^ I would guess if you buy from a guitar parts retailer the Bourns pots would be fine. I probably just bought the wrong thing! As I said, apart from that, they seemed very nice. I'm usually just using Alphas for push-pushes at the moment.

ICBM · February 2022

Dave_Mc said:

I got a couple of Bourns push-push pots, which were pretty nice... but the taper was really weird. It said something like "D" on them, which I think is some kind of log taper, but it seemed to me more like linear (maybe even worse). Not much happened until the knob was nearly at 0, and then everything happened all at once. I think I made the mistake of buying them from CPC/Farnell, though they were called guitar pots...

D is true 10% Log taper - steeper than a standard A (Audio) 15% Log. As a tone pot it works better than an A, although possibly a bit too extreme for a volume.

A you sure they weren’t C (reverse Log) or maybe K (25% Log)?

https://www.planetz.com/potentiometer-tapers-graphed/

Dave_Mc · March 2022

ICBM said:

Dave_Mc said:

I got a couple of Bourns push-push pots, which were pretty nice... but the taper was really weird. It said something like "D" on them, which I think is some kind of log taper, but it seemed to me more like linear (maybe even worse). Not much happened until the knob was nearly at 0, and then everything happened all at once. I think I made the mistake of buying them from CPC/Farnell, though they were called guitar pots...

D is true 10% Log taper - steeper than a standard A (Audio) 15% Log. As a tone pot it works better than an A, although possibly a bit too extreme for a volume.

A you sure they weren’t C (reverse Log) or maybe K (25% Log)?

https://www.planetz.com/potentiometer-tapers-graphed/

Sorry it took me so long to get back to you- my modem died so I haven't had internet access for the guts of a week (then I had a ton of stuff to catch up on because of the lack of internet access).

I'll try to hoke the pots out... they're lying around somewhere, just have to remember where! I seem to remember they said "D" on them, but from what I remember it wasn't that clearly marked. They were definitely sold as "logarithmic"... and I had two of them, and both reacted like that (everything at the bottom of the pot's travel). I was thinking maybe I'd wired them incorrectly or something like that, but even for me, wiring two of them incorrectly?

EDIT: I found the pot, apparently it was easier to find than I thought (it's still just sitting on my table, lol). It says (best as I can make out, it's printed on it so a bit hard to see):

6*433
250KRD

* or G, it's hard to make out

I wonder if that "RD" bit means reverse D taper, like you said. I went to my old emails, and the link to the pot I bought no longer works, but I've got the code off that, too: BOURNS PDB185-GTR11-254C2 Potentiometer, Rotary, 250K Ohm, 17mm, +/- 20%

Again, I wonder if that "C2" bit in the code means the reverse log code (C) you mentioned...

Not sure I can be trusted around electronics!

EDIT #2: No, scratch that, I'm not sure if that's correct or not- looking at those graphs you posted (thanks!)- does reverse log have full output when the pot is at 0 and no output when the pot is up full? If so, that's not what was happening. I was getting near enough full output on the pot from 10 until about 1 or 2 (a very, very subtle reduction from 10 until about 2)... and then all the usual change which would happen along the full travel of the pot (even with a standard log pot) happened between 2 and 0. And that seemed to happen with both of them. It was kind of like linear taper, except even worse. Like super-linear, if that makes sense.

EDIT #3: Nope I was right the first time- I can't be trusted around electronics!

I think it must be C2 taper, that's what it suggests in the code in the email I got when I bought it, and I did some digging on the Bourns site and I think this is the pot: https://www.bourns.com/docs/product-datasheets/PDB185-GTR.pdf If you scroll down to page 4 there, it shows the tapers, and I guess the one I got is C2.

ICBM · March 2022

Dave_Mc said:

I was getting near enough full output on the pot from 10 until about 1 or 2 (a very, very subtle reduction from 10 until about 2)... and then all the usual change which would happen along the full travel of the pot (even with a standard log pot) happened between 2 and 0. And that seemed to happen with both of them. It was kind of like linear taper, except even worse. Like super-linear, if that makes sense.

Yes, that description is what a reverse log taper does.

Sell them to a lefty

.

Funkfingers · March 2022

The pot taper might also suit the Bass control in a G&L-style PTB circuit.

Dave_Mc · March 2022

ICBM said:

Dave_Mc said:

I was getting near enough full output on the pot from 10 until about 1 or 2 (a very, very subtle reduction from 10 until about 2)... and then all the usual change which would happen along the full travel of the pot (even with a standard log pot) happened between 2 and 0. And that seemed to happen with both of them. It was kind of like linear taper, except even worse. Like super-linear, if that makes sense.

Yes, that description is what a reverse log taper does.

Sell them to a lefty .

Yeah I was wondering what they would be used for, then I thought they might suit left-handers. Thanks

Funkfingers said:

The pot taper might also suit the Bass control in a G&L-style PTB circuit.

Thanks!

That's interesting, I always wanted to try that to see what it was like. Is 250k alright for it? Stock seems to be 1M, but I came across at least one site where they said they preferred 500k pots, so maybe 250k might be alright, too.

Funkfingers · March 2022

Never tried the PTB circuit myself. @ICBM is probably the best person to consult.

ICBM · March 2022

250K will be perfectly fine, just give less bass cut than higher resistances.

Sporky · March 2022

The G&L bass cut is brilliant.

In answer to the original question, have it switch in a moderate mid boost?

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One Humbucker, One Volume Pot Cavity - What Wiring Options?

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