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Coil Splitting Volume Loss Fix

Discussion in 'Pickups & Electronics [BG]' started by bluefizz, Jul 22, 2017.


  1. bluefizz

    bluefizz

    Aug 8, 2008
    Los Angeles
    MTD, Bartolini Electronics, La Bella Strings
    So, I was looking for a way to keep the volume relatively the same when changing from single coils to humbucker. My experience so far have been the singles are about half the volume (or close to that). I figured, humbucker, twice the coils, twice the volume.
    After looking around online I guess PRS installs resistors, but cant find anything about this issues for bass, or how/which resistors to use.

    I plan on wiring each pickup with an on-off-on DPDT.
    Up - North coil
    Middle - Humbucker
    Down - South Coil.
    Basically, I want the same volume between all three.

    Any idea??
     
  2. Killed_by_Death

    Killed_by_Death Snaggletooth

    Jan 2, 2015
    heart of darkness
    There's basically no way that a single coil can be as loud as two cols, so you'll have to attenuate the output of the humbucker somehow.
     
    David Jayne likes this.
  3. bassbenj

    bassbenj

    Aug 11, 2009
    When you have 2 coils in series it doubles he voltage output.That is about 6 dB. (note 3 dB is about the smallest volume change you can notice)

    To keep the levels the same is not so simple unless you have an active system somewhere where you can change the gain. Basically you have to pad down the humbucker mode to half voltage. Some Old G&Ls had resistors switched in to do this. I wired mine that way too. Bad news is by changing he resistance in the pickup circuit you change the tone. Eventually I took the resistors out for that reason. The other option is to wire the humbucking mode with parallel wired coils. This keeps the volume the same. Bad news is this ALSO changes the tone. For example I put a switch on my PJ so the two P pickups could be series or parallel so that they wouldn't be so much louder than the J bridge pickup. Bad news. I hated the parallel sound and never used it. End result you just have to use the volume control to adjust levels. Sorry.
     
    Killed_by_Death likes this.
  4. bluefizz

    bluefizz

    Aug 8, 2008
    Los Angeles
    MTD, Bartolini Electronics, La Bella Strings
    I kinda figured as much. I have 2 option when wiring that I want to take.
    Its either whats above, or series-single coil-parallel.
     
  5. 4StringTheorist

    4StringTheorist Supporting Member

    There was a thread here in this forum within the last week that discussed this. To do a series/single switch with no volume drop in single It'll take a 4PDT on-on-on switch. You'll lose a little bit of treble in series thanks to the resistors, but for some that's just more of a good thing, right? if you wanted sparkly, you'd have it in single-coil mode.

    I haven't really found any of that kind of switch in a push-pull potentiometer form factor, or I'd pounce on it. I still might. A bit reluctant to drill holes and add two switches to my control layout is all.
     
  6. bluefizz

    bluefizz

    Aug 8, 2008
    Los Angeles
    MTD, Bartolini Electronics, La Bella Strings
    You have the link to the thread?
     
  7. 4StringTheorist

    4StringTheorist Supporting Member

    There's this one where someone was talking about using a trim pot (a variable resistor) on the inside to dial in the gain difference. For a bit less $ you can just get a small set of resistors and use the ones that match the volume most properly.
     
  8. 4StringTheorist

    4StringTheorist Supporting Member

    This one too.

    Note: I think the switches in these threads are "on-on" rather than "on-on-on". My bad.
     
  9. Humbucker to single coil switching is not coil tapping. Tapping is an entirely different thing.

    To even out volume differences between settings, you simply put a resistor in series with the signal path for the loudest setting. Trim pots are ideal, as they allow fine tuning.
     
    David Jayne likes this.
  10. megafiddle

    megafiddle

    May 25, 2011
    If some series resistance is all thats needed to attenuate the series configuration, I believe a DPDT ON-OFF-ON switch will do it.

    This assumes a single resistance between the pickup and volume control.

    -
     
  11. Steve Dallman

    Steve Dallman Supporting Member

    I changed one of my humbucker guitars from coil cut, to the PRS, resistor limited cut and like it. I used a 1.1k on the bridge and 2.2k on the neck. The resistor goes between the switch and ground.

    Another possibility is to put a cap between the switch and ground. This cuts the highs from one coil but the bottom (and volume) remains. I always used .02uF for the cap, but with bass, some experimenting may be necessary. .047uF might be a good place to start. You get the high end of single coil, but the low end of the humbucker, plus the pickup still bucks low frequency hum. The larger the cap, the more highs (and mids) are cut.
     
  12. bluefizz

    bluefizz

    Aug 8, 2008
    Los Angeles
    MTD, Bartolini Electronics, La Bella Strings
    How would you do this at the switch with out effecting the single coils? (Since obviously the humbucker is going to be the loudest)
     
  13. bluefizz

    bluefizz

    Aug 8, 2008
    Los Angeles
    MTD, Bartolini Electronics, La Bella Strings
    How did you choose a resistor size? Would it be the different between the ohm reading of the single coil vs the humbucker?
     
  14. For north coil/series/south coil, you typically use one pole of a DPDT On/Off/On switch. You can use the second pole for the resistor switching. Start by putting a resistor in series with the output of the switch. Then join both throws of the second pole together and wire them to one side of the resistor, and wire the common terminal of the second pole to the other side of the resistor. The result of this is that the resistor will shunt in the single coil positions, but stay in the circuit when you are in the humbucking position.
     
    Killed_by_Death likes this.
  15. Resistance is best chosen by trial and error. Hence, it is usually best to use a trim pot rather than a resistor of fixed value.

    Note that the resistance of your pickups doesn't really tell you anything at all. People just like to toss those numbers around because they are easy to measure.
     
  16. bluefizz

    bluefizz

    Aug 8, 2008
    Los Angeles
    MTD, Bartolini Electronics, La Bella Strings
    I ordered 2 DPDT on/off/on switches and plan on using the wiring from page 3 of the bartolini wiring -
    https://www.bartolini.net/wp-content/uploads/2013/12/4-Conductor-Wiring-Diagram.pdf
    I understand some of what you said to do, but not all. Do you have a wiring diagram written up?
    I also like the idea of a trim pot instead of a fixed resistor, but every trip pot I find has 3 poles (I've never had to wire in a trim pot). Not to sure how to go about that.
     
  17. I'll draw a diagram when I get a chance.

    The third terminal can either be left open, or shunted to the wiper.
     
  18. Killed_by_Death

    Killed_by_Death Snaggletooth

    Jan 2, 2015
    heart of darkness
    The three terminals are pretty simple to understand. There's a wiper in the middle, which is the center terminal.
    As you move the dial, the resistance gets greater on one side (for instance terminals 1 & 2), and less on the other side (terminals 2 & 3).

    main-qimg-e41a6d46e6033c64b92226aa3f382820.

    A trim pot is electrically the same as the pots you use for volume & treble cut, but in a smaller form factor.
     
  19. bluefizz

    bluefizz

    Aug 8, 2008
    Los Angeles
    MTD, Bartolini Electronics, La Bella Strings
    That would great!
    I've seen a lot of people talk about using trim pots, but have yet been able to find any wiring diagrams. The only ones I've found for resistors were for north coil/humbucker.
     
  20. bluefizz

    bluefizz

    Aug 8, 2008
    Los Angeles
    MTD, Bartolini Electronics, La Bella Strings
    So correct me if I'm wrong, but wiring A and B to the output would be in series, and W would go to the open pole of the DPDT switch (like line6man said), or it can be left open if I don't run it to the switch?