p-rails spin-a-split question

mudpuppy

mudpuppy

New member
I was wondering how to wire a set of p-rails with spin-a-splits so that it is the rail coil that is being shorted, giving anything from series HB to P90 on both bridge and neck pickups. Looking at one of the Duncan diagrams, it's not clear to me which coils are being shorted.

The reason I ask is that everybody raves about the humbucker and P90 tones from the p-rails, but there seems to be less enthusiasm for the rail (singel) coils. I'm a huge fan of triple shots (after installing a set today), but if you don't care about the rail single coils, spin-a-splits might be a more versatile option.
 
Re: p-rails spin-a-split question

That's part of the reason I never followed Duncan's diagrams (and wound up wiring stuff wrong anyway :lol: ) - when they show "Up" on the diagram, are they showing "switch lever up" or "upper contacts"?

Looking at the switch in the P-Rail diagram, I'd assume that flipping the switch lever up would activate the middle (R+W) and bottom (Grn+Bare) contacts, thus shorting out the R+W. However, the diagram doesn't clarify which wires are for which coil.

If we assume that the R+W are the Rail, then the diagram shows the Rail being shorted, leaving the 90 active. But, it's time-consuming to rewire it if it doesn't come out right the first time.
 
Re: p-rails spin-a-split question

I think I may have found the info I need from the SD FAQ. The B/W pair is for the Stud/Inner coil and the R/G pair is for Adjustable/Outer coil. I should be able to wire R&W to the spin-a-split pot and simply reverse B&G (black to ground, green as signal out). If B and R/W are both at ground, then the B/W coil = inner = rail should be shorted when the split pot is a zero ohms. I think I got that right, but would appreciate anyone checking my work.

I don't always agree with the diagrams either. I always wire signal-in (from pickup) to the wiper on volume pots, vs. how SD usually wires signal-out (to switch) to the wiper.
 
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Re: p-rails spin-a-split question

On P-Rails, the Rails coils are always red and green, the P90 coils are black and white
 
Re: p-rails spin-a-split question

So if you wire R+W to be shorted out as the split function, you get.....? Rail? 90?
 
Re: p-rails spin-a-split question

frankfalbo said:
On P-Rails, the Rails coils are always red and green, the P90 coils are black and white
Click to expand...

Thanks frank. I guess that means that going with the (unmodified) diagram that I referenced will give you P90 tones when split, since both rails wires will be at ground potential with the split pot at 0 ohms.
 
Re: p-rails spin-a-split question

Just had a thought. You could use a 4PDT switch to swap black & green wires from the pups before going to the vol. pots. That would let you also have access to variable rail/HB splits as well as P90/HB. You could always use two DPDTs, but half of the combinations would have bridge and neck out of phase. I think a 4PDT would be a simpler and better solution. Does anyone make a 4PDT push/pull pot? I'm thinking in terms of standard Gibson contol layout, so using a couple of concentrics and a push/pull or two seems to have the potential of being even more versitile than triple shots in some respects.
 
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