Which pots for coil blend / spin-a-split?

[MrBaens]

<t>I recently bought a player series jaguar having seen on here that the cavity is already pre routed for dual humbuckers. But I missed the look of the chrome switches so decided it would be my holy quest to add both switch plates back to the jag and find a use for all of them!<br/>
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So with humbuckers I’m not going to have much use for the rhythm circuit. But I did start to think about ways to get back some of the single coil sound. Splits? Treble bleed? Partial split? Oh the possibilities, but most exciting among them is the potential for variable coil splitting, aka spin-a-split. <br/>
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I had a chat with folks over a montys guitars about which humbuckers I could use to still get a decent split coil sound, and ended up ordering a set of overspun-PAFs and a vintage oil + paper capacitor for 50s wiring (in place of a treble bleed. They’re on the way now but I still don’t know what to do for the pots! <br/>
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I can order a chrome upper plate and a mounting shelf and rollers (to see if it will fit in the single switch hole that’s been routed) but I’d rather not have to dig out the power tools especially for a switch that I don’t know if I’ll need. I know I should use no-load pots. Will it alter the tone significantly if I use the regular 500k 1M pots from a rhythm circuit? Should I swap out the pickup selector for the traditional 3 switch plate so that the strangle switch can turn on the coil split circuit? <br/>
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Sorry for the long post, I think I’m going to wire in the bridge humbucker next weekend but ordering a new scratch plate etc might take months so I’d love to hear your take on it!</t>

[Ceylon]

I'm not knowledgeable about this enough to give you any better answer than that the HH Classic Player Jaguars from Mexico does exactly that with their rhythm circuit roller, turning that switch into a kill switch and having the rest of the control be standard Jaguar, so I would maybe look into how they did it

[MrBaens]

I found this diagram for that, which suggests they have both a strangle switch and a coil split on-off. Which is good to know (as maybe this is there to avoid constant tone problems) but no notation there on what the pots are… from the look of other posts ( like this ) they use regular rhythm circuit values? Maybe that’s why that button kills the circuit to mitigate any unwanted tone issues…

[timtam]

That version of Fender's parts list for the CP HH jag is wrong. How could you get the same split on each pickup with two different pots, the same as the rhythm circuit volume and tone pots ? They're actually both 50k linear. This is the correct version:
https://www.fmicassets.com/Damroot/Orig ... Manual.pdf

Like on the Vintera 60s Modified. They both also have a slightly different strangle switch circuit.
https://www.fmicassets.com/Damroot/Orig ... 4_2019.pdf

[bodhi]

With the spin-a-split mod the effective resistance range where you can hear any difference between series and single-coil sounds is very narrow. I'd suggest ordering a couple each of 10k or 25k pots and temporarily assemble them for just the blend sounds to see what kind of range you find useful. With 1M or 500k pots the range of blend sounds is going to be pretty narrow, but of course it's good to experiment for comparison's sake.

There's a bunch of things you can achieve with the existing controls, and some that might make sense with alternative control plates. If you have the patience for it, actually trying all sorts of different variants out might be the best way to narrow down what actually sounds best or most interesting or different with the current gear that you have. You can use small plastic breadboards and components to wire up alternatives quickly, instead of soldering everything up, if that's your kind of thing.

I have taken to ordering humbuckers with slightly unbalanced wiring across the coils with my projects, to have better split sounds available. Something like a 5% overwound on one side in comparison to the other seems to work out so far. But the only time I've used spin-a-split wiring has been with a Peavey T-60 style wiring on a Wide-range equipped Tele (essentially a Tele Deluxe thing), so that when the tone pot is turned up completely the pickups are in single coil mode. With 500k tone pots, the range is maybe all of 10-9 on the pot, but there are some minute shades there. But it's more like going between a humbucker turned to 9 on the tone pot and a full single-coil sound than anything inbetween. With the jag setup I'd perhaps not try integrating that directly to the tone pot, especially if you're not going to use the rhythm circuit as is, since it'd be straightforward to toggle between split sounds with some other setup. All up to preference and exploring, though!

Treble bleeds on humbuckers don't produce single-coil sounds

[MrBaens]

oh amazing stuff bodhi!

Ok I ordered up a pre-assembled rhythm circuit + plate (it was the same price as just ordering up the plate, mounting bracket and rollers so eh free pots). First step will be adding in the bridge humbucker.

Step two might just be to replace the scratch plate and add in the traditional control plates. Now with the neck humbucker attached. The three switches being two pickups and one master coil split. At the same time I learn if the wheels fit without additional routing.

Then I add the 50s wiring. I'll likely order new mini pots (just mini pots with the right value are ok not like weird sizes or anything?), maybe I decide I need to get the drill out to add a hole for the upper switch to sit in. Either way a fun experiment. I'm not trying to get a single coil sound, but just a range of sounds that I actually use and makes use of all the knobs and switches.

I'm not sure what the breadboard adds, is soldering that hard?

[bodhi]

I don't find guitar soldering difficult, the breadboard idea is mainly related to being able to make changes easily rather than needing to disassemble the guitar. I'd suggest testing changes out in a playing position, and practically with Fender style guitars the body is routed from the front and electronics are covered with pickguards, so depending on the guitar it's a bit of hassle to test alternate wiring configurations.

Oh, and a note on my previous text, the tone pot with the spin-a-split wiring has audio taper. With a linear taper it would probably amount to more or less an on-off effect at the extreme, I'd imagine.

[MrBaens]

ok. audio taper, lowest load I can find. What I'm understanding is that the pot's aren't really going to affect the tone but that's the problem, I just won't hear the result.

Last question (actually showing how little I know about pots), if I get some 10k or 25k pots in there, that'll give me a range between what and what? Naïvely I'd think all the way on would be full humbucker and all the way the other would be full split. If I add a switch (like in the HH specials) and in full humbucker mode (on the wheels) would there be a difference between on and off? is the number the minimum resistance or the maximum? So when closed nothing gets through, but when fully open I'm still going to have a 25k resistance? which gives a 'partial coil-split'. I mostly want to protect the full humbucker sound.

[bodhi]

The taper is significant in the Peavey T-60 type wiring since the resistance value is so large compared to what you need, so actually having something else than an on-off is relevant.

Cross-checking some other websites, I can't seem to find anything completely definitive with regards to the potentiometer resistance value. But some posts elsewhere suggests using a 50k pot to get the full range, and some 25k... In any case, it seems that the interaction is "fully humbucker" by around 40k at the very latest, according to what I just read. Can't tell for certain, I haven't tried those values in particular. Pots are fairly cheap, though, so you could just get a set of different values to try out. There is probably some kind of relation of the potentiometer value to the resistance in the coil of the humbucker itself as well...

Regarding the range, essentially what the mod does is kind of a "variable coil split". A typical humbucker is essentially two single-coil pickups connected together in series, but wound in reverse between the pair. If one half of a humbucker is connected to ground, you only get one side of the pickup, which is a single coil. In a typical setup for a coil split, the ground reference for the other half is a switch, so you go from full ground to nothing. Now, the spin a split mod instead introduces variable resistance at that same spot between the coils of the humbucker, moving between nothing and comparatively much. Technically, there is probably some interaction with the spin-a-split pot and the humbucker even if the pot is turned up all the way, but I can't say since I haven't explored this in my own usage, and the 500k pots have little interaction when turned down. You can of course use a switch or breadboard connections to compare sounds, it might be much more significant with lower value pots. Some people seem to argue that you should cut the trace of the potentiometer to remove the interaction completely. But this might not be all that relevant until you do a potentially "permanent" installation.

So, it might be best to get a few cheap pots of different values to experiment with, probably with a linear taper at least if you're trying the very lowest adjustment range, so you have an easier time to return to specific ranges if they're playable. It may f.e. be that the most usable end result is one or a few different values that give significant changes to sound, that you might f.e. wire up to the lead/rhythm switch, and then use the rhythm circuit pots for something else in the end. Who knows?

[MrBaens]

Great reply again thanks. I landed on this option, (coil blend pots and a switch) after a fever dream of looking at possibilities. I’m enjoying the coil split switch that’s in there at the moment but by big consideration was that I wanted all three control plates. Ideally functional.

Any other options I could add (other than a rhythm circuit, treble bleed, or coil blend)?

[bodhi]

Well, there's a plethora of options if you f.e. look at this marathon-thread here: viewtopic.php?f=8&t=104282

I'm not sure if someone ever compiled a comprehensive list of things one can do with guitar wiring, but a lot of the time everyone sticks to a pretty common set of variations. Varitones and other less common things don't show up that often or get forgotten about, so it's a field that can be interesting to explore. Some wirings might only be very situationally useful, or for specific genres etc., so it's difficult to tell beforehand, depending on what your needs or interests might be at the time.

[MrBaens]

Ok I think I feel my mind expanding and I think I finally get it. Thinking back to your description from before and jogging repressed memories of YouTube rabbit holes about no-load pots.

my roller knob is going from fully open which is no resistance so everything goes to ground so single coil to fully closed which is the resistance value stated on the pot. You're saying that a 1M or 500k pot will be a high enough resistance that even at 1/10 open will still be enough resistance to not let any signal through so will count as a full humbucker. So it will basically act as a switch from single coil to humbucker. Ok I think I get that, it's also something I can try out without ordering any new pots.

So Ive seen people modifying pots by opening them up and cutting out the last 2mm of the resistance track to make a no-load pot. and I was trying to work out what this is for...

Ok so what you recommended was looking into pot values of 10, 25, or 50k such that I actually get a variation in the resistance value. Fully open is still single coil, but fully closed will still loose some signal to ground. This is what I was afraid of, a true single coil but forever tarnished humbucker sound.

but this is where the no-load pot comes in. I should aim for a pot that gives a nice range where fully closed is *almost* the full humbucker sound and give it a boost by cutting the transition between 9 and 10 on the pot to be 90% resistance and full resistance (no connection). There will be a slight jump but I will get a pure humbucker tone at the end without having to perfectly match the pot with the pickup. This will be the same as including a switch that bypasses the circuit. 10 on the roller should equal the switch being off, but 9 should be audibly different. This is then directly related to the output of the pickups. Mine are especially hot, reading an approximate DC of 9.1k at the bridge and 8k at the neck.

[MrBaens]

Hmm I can’t seem to find 10k or 25k pots that would fit. From the part list thet timtam posted (thanks!) I managed to find 50k linear ones. Any tips?

That’s even after realising that I will need to take a drill to the upper cavity to get anything other than the stock switch to fit up there.

[bodhi]

I believe typical 16mm pots such as f.e. Alpha should work, and I can at least find them locally (in Europe) off the shelf. You might have issues with getting the roller knobs to fit unless you order 6mm ones or try to get the knurdled ones and cram the imperial-sized ones on there (if it works, can't recall). F.e Eyguitarmusic should have the knobs and such, but it'll take a while to arrive.

In any case, I'd suggest trying it out with whatever you can get your hands on quickly before committing to routing. You can probably MacGyver the pots into place on the outside of the control plate with double-sided tape, for example. Another idea would be to attach a parallel resistor across the pots, which will bring the resistance value into the desired range, but this also affects the taper.

[MrBaens]

Just as an update. All working well. It was a massive stress to take the drill and chisel to the body to extend the cavity out to fit the pots in the top control pocket. But worth it. I now have two pick up switches and the third activates the coil blend circuit. Still need to get the nice low resistance pots but I’m generally very happy. With the sound (and look)