Using 250K pots on Humbuckers

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by Scott Peterson, Dec 13, 2005.

  1. Scott Peterson

    Scott Peterson Staff Member

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    I have owned my main guitar - a Melancon Custom Artist - since the summer of 2004. The thing is a monster. Nothing I have ever owned comes close, IMHO, to the tone of this thing.

    I have Wagner SR/SR/Goodwood pickups. (S/S/H). The electronics are stock from Gerard. The SR's are fantastic single coils, but what gets me about this particular guitar has always been the richness of the Goodwood humbucker.

    I was inside the electronics looking at it, honestly trying to find out why it sounds so damn rich. Nothing fancy in there - even a ceramic cap.

    But then I noticed the volume pot is a 250K pot.

    Now I have fiddled with guitar electronics since I was a teenager, but it never struck me to use a 250K pot with a humbucker. I always just assumed 500K was it when using a humbucker and you use 250K with single coils.

    My question then to those who know - what effect is this pot having on my humbucker?

    And, since I dig this sound so much, should I just get 250K pots for all my humbucker loaded guitars to see if it sounds better? Does it make them brighter, darker, louder or what?
     
  2. scottl

    scottl Member

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    I use 250k pots on my hums.... Gene Baker was doing this for most of the hum guitars he made. The 250k pot loads the circuit more. The tone is usually less gainy and it may move the pickups frequency peak lower or down a bit. The pickup also stays clearer when rolling off. That is a big one. Gainiacs may prefer 500k or even 1M as you do get a brighter and gainier tone with the larger value pots.

    All you need to do is add a 500k resistor across your pots outer lugs to simulate the effect. You want to try 750k or even 1M to get in between pot values per taste.

    Scott
     
  3. sundaypunch

    sundaypunch Member

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    IIRC, the larger value will give you more high end. Using a 250k with a humbucker rolls off some of the high end. Single coils generally have a 250k pot since they are a bit brighter to start with.

    I actually like most of my humbucker guitars with a 250k or 300k pot.
     
  4. Scott Peterson

    Scott Peterson Staff Member

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    Fascinating. I am hoping this thread really schools me on this - I feel a round of mod'ing coming on. Warm up the soldering iron!
     
    James likes this.
  5. Jim Collins

    Jim Collins Member

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    As the value of the volume pot increases, you will see more highs when the volume control is on full, but you will also see more highs rolled off when the volume is backed off. In other words, if you were to use a 500K pot in a Strat, where you would normally see a 250K volume pot, the guitar would be brighter with the volume pot full on, but would lose quite a bit of the highs as you backed off on the volume. With a 1Meg pot, both of those effects would be more pronounced. (That is why you frequently see a treble bypass cap, or a bypass cap/resistor in a single coil guitar with a 500K or 1Meg volume pot.)

    The same holds true for humbuckers, but humbuckers are better able to withstand it. Using a 250K volume pot with a humbucker is not all that unusual. As scottl pointed out, Gene Baker did it with many guitars. Gibson has been using 300K volume pots in their production guitars (not the Historics) for quite a few years. Vintage guitars used 500K for both volume and tone. I believe modern Gibsons still use a 500K pot for tone. The net effect of using a 250K or 300K volume pot with a humbucker is a meatier sounding tone, with less treble rolloff as you back off on the volume.
     
  6. Zexcoil

    Zexcoil Vendor

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  7. AaeCee

    AaeCee Member

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    I've been contemplating these complexities for years, but never really experimented enough with altering my combinations. But this begs the question...how many of us have made the simple-minded (and yes, I include myself in 'us') decision to swap pickups, a potentially easy and apparent fix, when we should have taken the time and effort to consider the relations of all electronics first. My guess is that many of us would still be using our original pups had we tried different pot values first. I've done this a few times and eventually dialed in a great tone w/o pickup changes, but have changed pickups more often when looking to alter the tone, maybe mistakenly. IMO, if your pickups are already close to that ideal you're searching for, altering pot values is the most likely route to getting you all the way there. AC
     
  8. Clorenzo

    Clorenzo Member

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    Frequency response of a typical PAF with 500k volume and tone pots:

    [​IMG]

    250k volume and tone pots:

    [​IMG]

    As you can see, the value of the pots determines the amplitude of the resonant peak.

    I produced those plots with my guitar volume and tone circuit simulation spreadsheet which you can download here:

    www.harryj.net/voltone.xls

    Note that it only works if you activate a couple of Excel Add-Ins. Go to Tools -> Add-Ins... and check "Analysis ToolPak" and "AnalysisToolPak - VBA".

    This article:

    http://www.buildyourguitar.com/resources/lemme/

    explains the behaviour of a pickup from the point of view of its equivalent electrical circuit. Very interesting reading.
     
  9. Scott Peterson

    Scott Peterson Staff Member

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    Wow - ask and ye shall receive.

    Thanks guys!
     
  10. RL in Fla

    RL in Fla Member

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    Good (or bad) example : I got 8 "stock" CTS jobs in the mail today .


    Four 500's - 465, 512, 525, 530
    Four 250's - 207, 235, 240, 255


    Had on hand CTS -

    2 250's - 269, 270
    1 500 - 482




    With P90's try the 525/530 for the tones and 269/270 for the volumes ??
     
  11. Scott Peterson

    Scott Peterson Staff Member

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    Just as a follow through, I dropped a 300K volume pot in my Thorn and lordy, you guys are so right.

    Smoother, much more usable through the entire range of the pot. That big treble falloff you can get with out a bright cap on the volume pot.... MUCH smoother. Nice!

    I think I have found the path to my happy place now. Thanks so much!
     
  12. aleclee

    aleclee TGP Tech Wrangler Staff Member

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    Joe Driskill shipped (ships?) his guitars with 250K pots. I've been happier since replacing them with 500K units.

    Different strokes . . .
     
  13. TheArchitect

    TheArchitect Guest

    I have used 250k on virtually everything with the exception of my Les Pauls and PRS. The 2000 Paul has 300k which work nicely. I have been trying to work with the 500k in the PRS and for clean sounds they are fine but when I hit the gain channel it gets painful. I just picked up some 250k CTS pots today to make the switch on those guitars. I've never found 250k to be dull or contrained personally. I can see how a tele player might see it that way given all of the natural highs in that style of instruments but I don't find it to be the case.
     
  14. TheArchitect

    TheArchitect Guest

    So you removed the bright cap? I have been pondering whether to keep it on the PRSi when I make the switch on them.
     
  15. whoofnagle

    whoofnagle Member

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    Scott,

    I too dig 300 K pots. I have them in a tele with 2 P90's and in a tele with a P90 in the neck and an HD S90 (or whatever they call it) in the bridge.

    They both are smooth!!

    Bill
     
  16. axpro

    axpro Member

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    +111 on using 250's with HB's, makes em a little chunkier on the low down.
     
  17. 1959burst

    1959burst boogieman

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    my ears love 500k for humbuckers of the paf variety.
     
  18. ChrisB

    ChrisB Member

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    I changed to a 250k on a guitar with a Duncan JB and Bardens and much prefer the sound. The guitar is quite bright naturally though.....
     
  19. cswolfe

    cswolfe Guest

    Killer thread. Thanks, guys.
     
  20. cswolfe

    cswolfe Guest

    A line I don't understand from the article Carlos refers to: For some reason, I cannot seem to cut and paste it.

    It says some single coils are equipped with a coil tap switch. Alright, me confused. If you have a single coil, with a coil tap switch, isn't that called an "off" switch? ;)

    What am I missing here?
     

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