Jazzmaster wiring with dual coil Gold Foil pickups?

[jb1984]

Humbly asking for idea validation on my newest pickup wiring obsession... once I have the idea locked down, I should be able to work out the wiring, but I was hoping to get feedback before I start buying parts 

I just placed an order for two dual coil Gold Foil pickups.  Each one has one Guyatone-voiced coil, and one Dearmond-voiced coil.  They can be wired to use either/or and both in series.

These are going in a Jazzmaster, as I think the stock control configuration will be able to handle what I'd like to do with these pickups.

Does the following control scheme seem feasible - and better yet, useful - and/or are there are some potholes ahead that I should be aware of?  Or, if it's just plain too much trouble for not enough payoff, a reality check is welcome too!

Requirements:

1. Each pickup to be able to be used as either the Guyatone coil isolated, the Dearmond coil isolated, or both coils in series.
2. Want to have the ability to blend between the two coils in each pickup, with the coils connected in parallel.  Ideally without creating additional load.
3. Should have ability to have different coil blends in each pickup.
4. Need ability to switch to a "series pickup" mode easily.

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The plan:

• Repurpose the Rhythm circuit volume and tone pots to be blend pots for each pickup instead.
• 3-way toggle behaves as expected (N / N+M / B, however the individual pickup coils are connected at that moment)
• Rhythm/Lead slider switch flips between both pickup's coils in parallel, connected in parallel together, or both pickup's coils in series, connected in parallel together.

Two issues I can see arising with this:

1. Adding in two blend/pan pots might create additional load on the pickups, mucking up the tone.  I'm pretty sure I've seen this worked out by using something like a 100k M/N blend pot - is that correct?
2. One combination that won't be available is having, say, the Neck pickup as a single coil or parallel coil mix, and the Bridge pickup in series humbucking.  Not sure if this would be necessary because of the likely volume difference between the two.

If "problem b" is worth trying to accommodate, I could get one of those 6-way Freeway toggle switches, that could have parallel coil N / N+B / B on one side and series coil N / N+B / B on the other side.  That would leave the Rhythm/Lead slider kind of useless.  Maybe that becomes a blower switch?  Strangle switch?


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I appreciate this forum for all of the information shared - so just throwing this out for consensus - what would you do here?  Is it worth trying to accommodate all of these blended parallel and series edge cases, or should I just slap two DP3T slider switches for each pickup on there and call it a day?

Here's a quick diagram of my thoughts for the control layout if that helps cut through the inane verbosity above:

Any insight appreciated!

[newey]

I don't know offhand how many poles are on the stock lead/rhythm slider, but I don't think it'll have the poles needed to do this:

Rhythm/Lead slider switch flips between both pickup's coils in parallel, connected in parallel together, or both pickup's coils in series, connected in parallel together.

Let's let other weigh in, but I'm envisioning a 4-pole slider being needed to do so. Whether you could find a 4-pole slider switch isn't the issue, you probably can. The issue is, can you find one that will fit the stock opening, stock screw spacing, stock cavity size, etc. Not sure about that, it would need to be looked at carefully.

If these pickups are HB-sized (as I suspect), one option might be to use 2 of Seymour Duncan's "Triple Shot" pickup rings to handle the series/parallel/single coil switching for each pickup individually. Not quite sure about how you would integrate the blenders with that, though.

[jb1984]

Thanks, Newey.  You helped me realize that the Rhythm slider switch does need 4 poles to flip both pickups into a series mode.  I found a 4PDT switch on Mouser that has the same mounting dimensions as a standard Jazzmaster switch, but slightly taller, so I ordered it and we'll see if it fits or maybe just needs a little shaving to fit.

That also helped me realize that I probably have been chasing the wrong set of outcomes with this wiring - a humbucker, in parallel, and panning between the two coils probably isn't as useful as a humbucker in series, panning between the coils.  That way, I'd end up with single coil modes for each voicing, and a blend into series humbucking, weighted on either side, with the center position being the normal humbucker sound.

Doing it the way I stated earlier - wired in parallel, and fading out one coil or the other - would be OK, I guess, but probably not real useful in the in-between positions and the middle, if usable, would probably be much less useful than a spin-a-split single.  I guess if parallel really sounded good then I could make a case for working that state into the whole thing, but it's complex enough as it is.  

Those Triple Shot rings look really interesting.  These particular pickups are Novaks and are a custom size, so I'll have to either use his humbucker ring, or mount directly to the pickguard.  I wish there were a way to tap into the wiring of the Triple shots so you could modify phase and splits to be HOOP or partial split instead of 100% one way or the other.  They won't help me here but I have a Les Paul that I could see those being a good solution for - so thanks!

(The Novaks in question, if anyone else is interested: www.curtisnovak.com/shop/m-s-goldfoil-humbucker/)

I guess I'll have to see how it all shakes out when I start wiring the combinations together - my current thought accommodates these possibilities:

• Neck, single coil Guyatone voice
• Neck, single coil DeArmond voice
• Neck, panned somewhere between the two coils, in series (spin-a-split)
• Neck, 100% / 100% in series
• Both pickups combined in parallel, with whatever internal configuration they happen to be set at
• Bridge, single coil Guyatone voice
• Bridge, single coil DeArmond voice
• Bridge, panned somewhere between the two coils, in series (spin-a-split)
• Bridge, 100% / 100% in series
  

I feel like I've read through enough examples of spin-a-split wiring with blend pots to see that I can probably get away with an ungrounded M/N pot - and I can get 100%/0% settings at the extremes of the rotation if I modify the pot like a No-Load tone pot.  Seems like 100k is the area where people have found the sweep of blend to be usable - can anyone confirm whether that seems to shake out or if I've gotten off track with that idea?

For posterity, I'll post the wiring diagrams of whatever I land on when I sort them out for anyone looking to pursue the same kind of wiring scheme, 

and also for sanity check.  

[jb1984]

Wanted to post an update here to track progress for posterity in case anyone ends up looking to do something similar in the future.

I realized I hadn't been considering something: my original plan was to switch between a Series coil configuration (humbuckers), and a Parallel coil configuration that had a blend control to sweep between 100%/0% and 0%/100% of the coils, with 100%/100% in the middle.  What I wanted, outside of wiring jargon, was to be able to have one coil by itself as a single coil, the other by itself as a single coil, or both.

Wiring this in parallel, as I originally intended, would have given me the single coil settings on a blend pot, but everything in the middle would be pretty subtle shadings of the parallel coil sound.

A series configuration with one coil at 100% and fading the other from 0 to 100% seemed like a better solution.  The effect would be having a base single coil sound on the ends of the pot travel, and goosing it with a variable amount of the other coil until you reach full humbucker in the middle.

Instead of a traditional "spin-a-split", my plan was to use dual-ganged MN blend pots as replacements for the Jazzmaster roller volume and tone pots so that at either end, each coil could be had independently, and the blend could vary between favoring either coil.  What I didn't consider was that dual-ganged blend pots are a little larger than a standard 16mm pot, and the roller section is pretty jammed up for real estate as it is, with a lot of variation in the sizing for the pots/rollers/holes in the mounting bracket between USA and import Jazzmasters.  Mine (60th anniversary MIM JM) had the freakishly small mini-mini import pots, so I had to take a reamer to the bracket to widen the hole for 16mm pots, and order new rollers with a 6mm opening.

There's a thread on TalkBass regarding ungrounded blend pots with no-load modifications to avoid loading the pickups with additional resistance on top of the main volume and tone pots, and to remove any resistance in the 100% position - this was also a fairly easy modification to make, although, I'd suggest not trying to get the 2nd wafer out of the assembly - one was sacrificed to the solder gods in my first attempt.  It's do-able by removing the first wafer, cutting the trace, and then cutting the trace on the 2nd wafer through the housing.

Essentially, the blend pots become a 3-way switch at the ends and middle of travel, with variable coil-splitting between middle and end.  Since the pots do not have a connection to ground, a high resistance isn't necessary.  Most of the coil blend seems to happen between around 0-25k, but I wanted to start with 100k just to be sure, and since I had a few handy.

Fitting the MN pots was a different story.  The blend pot casing is larger to accommodate the two wafers, and the 100k MN taper blend pots I had were knurled shaft instead of solid shaft.

I thought I could get around this with a brass sleeve adapter, but because the spacing at the mounting bracket is so specific, I ended up having to shim washers on the pot to get the shaft positioned over the pickguard roller cut-out, and even still, it was a tight fit, and the rollers were getting a lot of friction after the pickguard was placed on the guitar.  I monkeyed with this for a couple evenings, and ultimately decided to pivot to a simpler spin-a-split configuration, with one coil permanently wired to hot, and the other coil wired to a linear potentiometer, with the same ungrounded/no-load treatment.

Since the Guyatone coil had less output, I figured that parking that on hot and bringing up amounts of the hotter DeArmond coil would provide the widest range of tones, rather than shading a hot coil with a weaker one.

The 4PDT slide switch from Mouser fits perfectly in a Jazzmaster rhythm/lead selector location. It's a little larger but didn't require any additional routing.  I also realized that by eschewing the "parallel" option, I probably didn't need 4 poles anymore.  They did come in handy, though...

After tinkering with this circuit and playing through it, a few issues arose.

• The "series" setting was on the woofy side.  This might be because the focus is on each coil individually, rather than generally as both combined.
• The in-between settings had a great spectrum of variation, but I saw the merit in being able to favor one or the other coil as the "fixed" hot coil.  The single coil setting was really great - not just a concession for something single-coil-like in a humbucker package, so being able to run both coils like this on a whim would be a useful option to have.
• The in-between settings also seemed pretty dark for an augmented single coil tone, especially compared to the full series mode with the spin-a-splits removed from the circuit.  Since the split ground was out of the equation, I also considered what happens when you remove resistance to ground in a normal volume pot configuration - you lose high end.  Maybe a treble bleed is needed.

To address the "woof", I added in some bass-cut caps in the Series configuration.  I landed on .047uf on the neck, and .082uf on the bridge.  These values seemed off from would be used for something like a "strangle" switch, but I needed a very gentle and low-end specific cut.  Having the extra poles on the Series/Blend switch helped to keep these bass cut caps from being involved in the blend circuit.

For the spin-a-split pots, I started with linear mini 500k pots that I had available, but the blend happens in the first 15% of the sweep, so it seems like 50k would be a much better option.  I faked this by adding a 47k resistor across the pots, but I'm sure the taper would be much better with a lower valued pot, considering the added treble bleed.

As far as the treble bleed goes, I suppose determining the best values will have to wait until I get the 50k pots installed.  I'm guessing something around 1.5nf with a series Kinman resistor would probably work well.

Ultimately, I feel like this is a good feature arrangement - and adding in a way to lock either the Guyatone or the DeArmond coil as the main platform tone would be the only thing I feel like I'm missing for this guitar.

The remaining issue to solve is finding a way to accommodate switching the stationary coil.  Finding a way to make the blend pots work in that constrained space would be a great option that wouldn't require adding any more external controls to the guitar, but keeping the simple coil-fader arrangement and adding a switch for each pickup to select the "fixed" coil would leave the roller pots open, which could then be used for an independent volume/tone control - so both the Series and Blended modes had their own.

I'll update with a wiring diagram once I've locked this down.