treble bleed volume pot mod question

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by johnmfer, Mar 14, 2005.


  1. johnmfer

    johnmfer Supporting Member

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    I was having hum issues in my heavily modified japanese jazzmaster with two mini-humbuckers, one 500k volume, one tone, 3 way switch. The guitar would hum all the time, humming worse with the volume at zero. A friend and I had the pickguard off this weekend and he suggested replacing the volume pot. I dug around in my spare parts box and found a 500k mini-pot from an '80s Washburn and tried that out. I noticed it already had the treble bypass mod soldered to it, but didn't see values on the cap or resistor (they were very tiny to fit the mini-pot and I was in a big hurry).

    The hum is gone! Whoo-hoo! However, the guitar sounds much much brighter now, bright to a fault. Those of you that have done this treble bypass mod, is it supposed increase the overall brightness of the guitar? Or is it possible that the faulty 500k volume pot was bleeding off my high end while humming like crazy?

    Unfortunately the guitar is now in the back of a van on the way to Texas for an upcoming south by southwest show and I won't be able to work on it until next week.
     
  2. alderbody

    alderbody Member

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    once, i tried the treble bleed mod on a strat and it became much treblier.
    And i couldn't believe why it sounded so bad untill i remembered i had this mod on, so i rushed to rip it off and the tone came back...

    it just don't seem to work for me. others like it.

    tone is really subjective. we all know that. :)
     
  3. rooster

    rooster Member

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    If your volume is on 10, the top of the pot and the wiper are electrically connected, and the resistance ought to be less than a couple of ohms, assuming the pot is functioning correctly. The capacitor is now bypassing a resistor of about 2 ohms or less, and will have NO effect on your signal, ASSUMING your volume pot is functioning correctly. Were I you, I would rip out all the pots and rewire from scratch using CTS pots, I usually get the Fender-packaged ones, because they only cost me $1 more or so. If you have a crappy pot that doesn't short at the end of the turns, than the bypass cap will now affect your tone.

    rooster.
     
  4. johnmfer

    johnmfer Supporting Member

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    Thanks for the advice! After getting back from texas I cracked open the guitar again and removed the bypass. The volume pot wasn't too happy with me parting it from its favorite cap and resistor after 20 years of being together and crapped out completely. So, I dug around and found the tone pot from the same guitar and installed that, only I think this one is linear taper, so still another one is in my future. Being at home I only played the guitar through my practice rig, so I haven't gotten a feel for if removing the bypass had an effect on the tone.

    Thanks for the advice about CTS, I'll probably pick some of those up at the shop here in a couple days and start over from scratch. Also, what I gather you're saying is it doesn't matter what the value of pot is (500, 250, etc) as long as the volume is at 10, because the resistance of the pot is close enough to zero?
     
  5. rooster

    rooster Member

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    Well, I wouldn't say that. The value of the pot can change the "attack" of the pickup. I generally stick to 500K on HB's and 250K on SC's. If you use a lower value pot, the pickup will get softer and warmer, and if you use a higher value pot, it will get brighter and louder.

    rooster.
     
  6. johnmfer

    johnmfer Supporting Member

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    Okay, cool. I'm familiar with the HB 500 / SC 250 rule of thumb, which is why I've been working with the 500s with the humbuckers. However, after reading your post it occurred to me that I had never heard/read whether or not the tonal differences were only at volumes less than 10.
     
  7. rooster

    rooster Member

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    It all depends how you have them hooked up. As you turn the volume knob down, you lose a little treble, which is why you put the capacitor across the pot in the first place. You get a little of that high-end rolloff by reducing the value of the pot. You can experiment with this by soldering a resistor across the pot legs to drop the resistance of the pot.

    rooster.
     
  8. dave251

    dave251 Member

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    Regardless of the pot value, there will always be signal bleeding to ground; ie, a 500K pot has a ground differential of 500K ohms when the pot is wide open, so SOME of the signal is ALWAYS lost to ground...the lower the value, the more signal is lost.

    But a 500K pot on a typical small single coil, lets WAY too much of the highs stay in your signal...TOO bright...that's why Strats and Teles use 250K pots...it sweetens them up quite a bit.

    Regarding the use of the volume pot, you will always lose high end first as you turn the volume down. That is of course the reason for the bypass cap as the high end, if balanced with the correct value pot/cap, should remain relatively even throught the travel of the pot. However, even pots vary wildly in their response, as do caps...a "typical" good component is still + 10% tolerance...so finding an exact match for your pickup system is the key....obviously this is totally impractical in a production environment.
     
  9. burner

    burner Member

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    I wired a .001 to my strat and instead of retaining the high end, it seems like it actually INCREASES it as I turn down.
    Way too bright.
     
  10. skylabfilmpop

    skylabfilmpop Member

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    If your tone cap is connected to the middle lug/output of the volume pot, the treble bleed mod brightens things across the board because its intended for a schematic where the tone circuit connects to the input/first lug of the volume pot and in doing so the tone cap slightly loads the pickups and rolls off som ehigh end. Either move the lead to the tone circuit ot remove the trenle bleed and things should work fine.
     
  11. teleking36

    teleking36 Supporting Member

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    Glad to see this thread has been resurrected.

    I've got a HB and a single coil in my tele. I had the standard 250k volume pot on the tele swapped out for an RS 500k superpot to accommodate the humbucker, but kept the 250k tone pot. the 500k works perfectly for the humbucker, but it seems like it opens up the single coil bridge pickup too much. is there any way to 'show' a different value to the bridge pickup when it's engaged?
     
  12. fumbler

    fumbler Member

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    Yeah, you can solder in a 500k resistor so that it's in parallel with the volume pot but only when the SC pickup is switched on. It'll sum to a 250k resistance which the SC will be happy with.

    But the "both pickups on" position will see 250 which might be too dark for you. The right way to do it is to use a super switch and have each position wired separately (I mostly work on strats) but I don't know if they make such a beast for tele's.
     
  13. teleking36

    teleking36 Supporting Member

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    there's a 5-way superswitch in there right now. i'll talk to my tech and see if he can work something out for me. thanks!
     
  14. Mike9

    Mike9 Supporting Member

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    Here's a H/S/S diagram showing a 500k volume pot and 470k resistors for the single coils. I've been using 220k resistors as my connection from switch to volume pot on Strats and Teles since all I can get from RS these days are 500k volume pots. This value was recomended to me by RS and I like this setup more than the 470k one, but you may like a different value - resistors are cheap and plentiful at radio shack and Teles are so easy to work on.

    [​IMG]
     
  15. Chazz

    Chazz Member

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    Kickin it straight outta jersey man!!!!
    i dont really have anything cool or exciting to answer any questions about treeble bleed circuits and caps or pentiometers or anythin like that but i do have somethin to say... TREEBLE BLEED CIRCUITS KICK BUTT!!! ...i recently (yesterday) soldered a treeble bleed 2 my fender starcaster that i modded and omg its amazing lol ...i have a red with black burst fender starcaster (pretty much a strat but with a different name) that i got for 180 like 11 months ago and i hand scalloped the neck and polyurethaned it even tho it was a rosewood fretboard and it wasnt really needed but i like the look of a gloss finish over satin, and then i put an all new black pickguard, whole entire tremolo, locking tuners, a graphite nut, output jack (now a switchcraft) and graphtech string trees so its now pretty much a completely different looking guitar with better playability and sustain which also never goes outta tune i might add =) ...then since the appeal of the guitar was increased i decided time to make the tone match its visual beauty but do so electronically so i replaced ALL the electronics with amazing quality parts and GFS 64 vintage staggered pickups (which by the way are the best deal ever cause they have AMAZING crisp, jangly, and warm tones with real gray fiber bobbins, staggered alnico 5 magnets, and vintage cloth wire leads and they are only like $65!!!), CTS pots and a CRL 5 way switch and vintage cloth wire... a orange drop .022 cap and two CTS 250k pots for the tone and a CTS 500k for the volume and WOW such a big difference over the crappy electronics that came stock!! Now my starcaster sounds like a stratocaster deluxe no doubt about it!! ...and i mean the guitar was great before the treeble bleed was installed but once i turned the volume past 8 it got very bassy and muffled and it shot so lown in volume u couldnt even hear the guitar at 6 and it was like 5-1 were pointlessly there since they did nothing and that bothered me cause i felt the electronics were to greatly set up and good of quality 2 have such a flaw with them so i figured a treeble bleed circuit would solve the problem quite efficiently, so yesterday i went to radioshack and got a simple ceramic disk .001 cap (which im kindda upset about cause i would rather an orange drop but its still amazing) with a 220k resistor and i soldered it in place in series cause i read that if u solder it in parallel it will actually CHAGE the taper of the pot and i didnt want that at all cause 500k pots for volume kick butt cause they give a high ouput when cranked at 10!! all i have to say now is WOAHH this treeble bleed circuit is awesome!!... my volume now works from 10 all the way to 2 and thats a good enough difference to me and if thats not enough my treeble is NEVER lost so there are NEVER times where it gets bassy or muffled and it just sounds more natural when turnin down the guitars volume and it remains jangly and warm all the way down the volume even down to 2 and i also decided since the pickguard was off i might as well well hook up the bridge pickup to the 2nd tone pot for more tonal diverse options and after those 2 simple mods (treeble bleed circuit and bridge to 2nd tone) my guitar is GREATT and i couldnt be happier =) ...but my main point is the treeble bleed circuit is an amazing mod 2 do to any guitar that becomes muffled or bassy as u turn the volume down!! and if u have a 500k pot i would suggest a 220k resistor with a .001 cap and if u have a 250k pot i would suggest a 150k resistor with a .001 cap... i mean its whatever u pefer cause its all ur own taste but i used a 220k resistor in SERIES with a .001 cap and the results are simply amazing and i really couldnt be happier!! ROCK ON PEOPLE!! =)
     

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