PRS's Coil Split Methodology

Discussion in 'Guitars in General' started by Alpione, Jun 20, 2019.

  1. Alpione

    Alpione Supporting Member

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    Hey all - looking into a variety of PRSs right now and one thing that keeps coming up is that their coil split functionality, at least on newer models, turns off a coil but adds 1500 turns to the remaining coil to keep volume and fullness up. Sounds cool and addresses one of the main issues with splitting.

    Is this unique? I imagine not, but I'm not familiar with it. If one was to swap pickups to non-PRS stock, would he lose that addition of turns and it would go to a traditional one-on, one-off setup?
     
  2. vibrostrat43

    vibrostrat43 Supporting Member

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    Yes, that's something unique to the pickups (possibly some extra electronics wiring is used to pull that off), but most humbuckers have each complete coil tapped off with the wires that go the rest of the guitar's circuit. Essentially, any pickup that wasn't made to what the PRS pickups do would not receive the benefit of the extra 1500 turns (this is a feature that's built into the pickup itself).

    There are some pickups that do a similar thing, but I'm not sure if they use the same method. Something like the Fralin Unbucker for example. It sounds like it's a different method to me (essentially each coil is wound with a separate number of turns so that when you tap the coil with more is similar in turn count to a traditional single coil).
     
  3. 2HBStrat

    2HBStrat Member

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    Where are the extra 1500 turns when the pickup is in humbucking mode? Are they out of the circuit?
     
  4. derekd

    derekd Supporting Member

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    Union rules.
     
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  5. CharAznable

    CharAznable Member

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    I presume the coil is permanently tapped until it gets split.
     
  6. traviswalk

    traviswalk In the Great State Gold Supporting Member

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    Hmmm, I never knew they did something different like that. I do think the single coil tone and loss of volume on PRS humbuckers are some of the best I've ever played. I got one of the Special Semi Hollows a few months ago and keep the neck bucker split and the rear bucker at full and it's works better than other guitars with a SSH setup.

    [​IMG]
     
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  7. sedawkgrep

    sedawkgrep Supporting Member

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    Are you sure they are tapping the coil this way? I've only ever heard of the resistor method used to partially cut one coil, a'la the DGT.
     
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  8. Alpione

    Alpione Supporting Member

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    I'm going by a few reviews I've seen recently from N Stuff Music on YouTube (who do a good job with them.) He covers that "1500 turn" feature when talking about the splits.
     
  9. sedawkgrep

    sedawkgrep Supporting Member

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    That 1500 turn thing gets repeated a lot and all I can find is a mention originally where PRS states something similar.

    Having said that, the CE24, DGT, and McCarty use three separate modern pickups (85/15, DGT, and 58/15 respectively). All have essentially symmetrically wound coils and all use resistors on the coil tap, so I think that's what's going on. Otherwise you'd have different pickups for the models which don't have resistor mods.

    Easy enough to test if someone has a multimeter. But it wouldn't behoove PRS to wind the coils that asymmetrically given how flexible they try to make them. If one coil is 10k and the other is 4k, a 5-way rotary (for example) is going to give you wildly different volumes (even more than usual) on the split settings.
     
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  10. Alpione

    Alpione Supporting Member

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    A note to Customer Service has been fired off! :) We'll see if they cough up the scoop.
     
  11. fr8_trane

    fr8_trane Supporting Member

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    Thats not how it works. Its actually very simple: they put a resistor in series with the coil cut so that not all of the signal from the coil is dumped to ground. Its a "partial cut" and it works great. Much closer to single coil tone, less loss of volume and less noise than a full coil cut. Not sure why everyone isnt doing it this way. Its an elegant solution.
     
    Last edited: Jun 20, 2019
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  12. sonofspy

    sonofspy Member

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    Perhaps this will help:
    Loads of humbucker-equipped electric guitars have coil-split switching options. The majority simply dump one of the humbucker’s coils to ground, leaving just one working. It can result in a rather thin single-coil tone.

    PRS recently started using quite an old idea (first suggested to us by guitar/amp technician Brinsley Schwarz). You simply add, in series, a resistor between the pickup ‘tap’ wire and ground. This mod, “doesn’t completely cancel the slug coil,” explains Smith, “it sort of three-quarters coil cancels. It allows some of the other [slug] coil through. It’s also slightly hum- cancelling.”

    PRS uses a 2.2k ohm resistor on the neck pickup and a 8.8k ohm resistor on the bridge pickup.



    ****Alternately, the late Brit luthier Sid Poole showed us a good one, using a 4.7k ohm variable resistor (sub-miniature fully enclosed carbon preset potentiometers from Maplins, 49p each) mounted onto the control cavity backplate. This enables you to dial in the amount of the ‘dumped’ coil you want to hear. ****

    I did THIS on my Parker PM20 except, I used it to add a small amount of signal from the Neck PU when the bridge is tapped and it is AWESOME. No longer tinny it has all the warmth of a strat.
     
  13. Alpione

    Alpione Supporting Member

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    Good details. Thanks.
     
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  14. David B

    David B Silver Supporting Member

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    I think the partial-split is most likely, and it is correct that this method of "partial-split/partial-humbucking has been around for a long time, it was something we often used in the 80's with HSS setups to make the #2 (bridge/middle) sound right for the "knopfler" sound. I use anything from 1k-4.7k depending on the pickup and the sound desired. PRS also has the "Tuned Capacitance and Inductance", which seems to be something different, and I am not sure if it improves splits of the partial-split method.
     
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  15. bgalizio

    bgalizio Member

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    This is interesting to me. I have a guitar with the humbuckers wired to individual mini toggles (no 3 or 5 way switch). I have those set to humbucker-off-coil split. Is it possible to rewire the coil split part with a resistor to achieve this type of sound?
     
  16. Bussman

    Bussman Member

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    You can achieve a controlled version of this partial split with Seymour Duncan's Spin-a-Split circuit.
     
  17. GreatGreen

    GreatGreen Member

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    Yes. Electricity takes the path of least resistance.

    Let's say you wind a pickup with, I don't know, 1 inch of wound up coil. If you route one wire to the top of the coil and the other at the .75 inch mark, the pickup will behave as if there's only .75 inches of coil wind because it can't flow through that extra .25 inches.

    PRS pickups get even single coil volume by overwinding one of the coils in that humbucker but not using all those winds until in single coil mode. The main thing they do that nobody else does for this pickup is that in "full humbucking" mode, that overwound coil is actually wired use only like 80% of its coil by tapping a wire into that point in the wind. Flipping to single coil mode means:

    A. turning off the other underwound coil
    B. routing an additional wire into the overwound single coil and using that wire as the wire that completes the circuit.


    Humbucker routing:
    Lead 1 hot, Lead 2 ground
    red = active winds

    [​IMG]

    Single coil routing
    Lead 1 hot, Lead 3 ground
    red = active winds

    [​IMG]



    Sorry for the horrendous "art" there lol, just banged it out in Paint to make it easier to visualize.
     
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  18. 2HBStrat

    2HBStrat Member

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    So, a tapped pickup basically like Schecter used to do back in the late 1970's? I have a PRS SE Custom 24 that has split pickups. I don't know if they're wired up the way you describe it, but I honestly don't know that ,if so, it's really an improvement over a regular split humbucker, which I what I use on other guitars. I supposed on a 2HB guitar it's more important that the "split" sound has comparable volume to the full humbucker volume, but on an HSS guitar there will already be a volume discrepancy between the humbuckers and the single coils, so when the humbucker is split it's actually more in line volume wise with the single coils.
     
  19. GreatGreen

    GreatGreen Member

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    There is a technical difference between "coil tap" and "coil split."


    A "coil tap" is what I described above where the wire is "tapped into" the middle of the winding.

    A "coil split" is when one of the coils in the humbucker is removed from the circuit entirely, making the pickup into a true single coil.


    Plenty of humbucker companies offer a "coil tapping" option which is where they tap into the entire humbucker with another wire somewhere in the middle of the winding. At "full humbucker" mode, the entire winding of the humbucker is used. Then when the humbucker is in "coil tapped" it means both coils are evenly tapped into somewhere in the middle of the winding, effectively giving you simply the same humbucker but with less windings, which typically results in less output and a higher resonant peak for a more "single coil-like" characteristic.

    The PRS system (that is, on that one pickup talked about in the opening post) does it a bit differently though because what they call "full humbucking" mode doesn't use 100% of the winding of both coils like most pickups use. Instead, they cut back on that one overwound coil in full humbucking mode so that when flipped to single coil mode, they can add those extra windings back into the circuit and minimize the volume drop. It's a really smart solution, actually.

    With you get into HSS sets all designed to go together though, designers then have the freedom to overwind the single coils or underwind the humbuckers as much as they want to make each pickup as close in volume as they can be. It's all a balancing act though. You can't increase or decrease the volume of a passive pickup without affecting its tonal characteristics and resonant peak, so there's only so much you can do per coil really.

    There's no clear "best" answer here though as each method sounds different and different people prefer different wiring. I personally like coil splitting, but that also comes with its own challenges, like that you really need to put an extra resistor in the circuit when you coil split to emulate a 250K pot system, otherwise they can get a bit ice-picky.
     
    Last edited: Jun 21, 2019
  20. xmd5a

    xmd5a Member

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    A common misconception about coil tapping is that if you take an 8,000 turn single coil, and tap it down to 6,000 turns, that it's electrically the same as a 6,000 turn coil, but in fact the 2,000 "leftover" turns act as an inductive load upon the the remaining 6,000 turns, which makes those 6,000 turns produce a darker sound than a pickup that has only the 6,000 turns, without those leftover turns. As a result, tapped coils tend to sound especially thin and weak, and that's why a seemingly very good idea has never been very popular.

    I don't know what PRS actually does, but I know that using a trim pot to dial in 4k - 8k resistance across the split to ground does make for a better sounding split humbucker. It pretty much solves the problem of splitting sounding too weak. The catch is that the precise resistance can be tricky to hit, you should use a trim pot, and make it accessible to that you can tweak it after the guitar is strung up and plugged in. The reason being that not only is it a matter of preference, but it's interactive with the particular impedance of the pickup, hence you'll arrive at different optimal values for the neck and the bridge pickups. A 20k trim pot gives you plenty of room to work with. I prefer this to a "spin a split", because the "spin" transition is not linear, and so that mod usually amounts to an "on off" switch in knob form.
     
    Last edited: Jun 21, 2019
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