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What audible effect does the resistor have on a treble bleed mod?

Discussion in 'Tele-Technical' started by 3-Chord-Genius, Apr 13, 2018.

  1. 3-Chord-Genius

    3-Chord-Genius Friend of Leo's

    Apr 3, 2015
    Winchester, VA
    I have one guitar that only has the capacitor (no resistor), and one that has both. Since they are two completely different types of guitars, I cannot compare them and draw any reasonable conclusion. In both cases, high-end is retained when the volume pot is rolled off, so they are both working. But I did the first mod without knowing that there is supposed to be a resistor in there also; the second one was done "properly". What effect does that resistor supposed to have on the tone?
     

  2. Smiff

    Smiff Tele-Holic

    582
    Oct 1, 2017
    UK
    Don’t know for sure; but there’s people who say a resistor value one quarter of the pot value produces a better taper on the pot. I guess this would be more noticeable with a 500K or 1 Meg audio taper pot than it would be on a 250K.
     
    Last edited: Apr 13, 2018

  3. JD0x0

    JD0x0 Poster Extraordinaire

    Age:
    28
    Feb 22, 2009
    New York
    A little vague. A resistor can be wired in parallel or series with a treble bleed, or not used at all, and they will have slightly different effects on the control.
     

  4. 3-Chord-Genius

    3-Chord-Genius Friend of Leo's

    Apr 3, 2015
    Winchester, VA
    Parallel in this case.
     

  5. luckett

    luckett Friend of Leo's

    Jun 14, 2011
    .
    With just a cap, it's a high pass filter with the lows being rolled off at 6db/octave all the way down. Adding a resistor in parallel creates a shelf and lets the lower frequencies pass through below a certain frequency. The frequencies at which it's happening are dependent on the values and interaction of all the specific components in your guitar. There is not much difference between the two as you just start to roll off the volume and the difference gets bigger the more you roll off.
     

  6. 3-Chord-Genius

    3-Chord-Genius Friend of Leo's

    Apr 3, 2015
    Winchester, VA
    Thanks. That's precisely the information I was looking for.
     

  7. Old Tele man

    Old Tele man Friend of Leo's

    May 10, 2017
    Tucson, AZ
    It "shifts" the point where higher frequencies are passed; changing C can do exactly the same thing.
     

  8. maj34

    maj34 Tele-Meister

    266
    Nov 19, 2013
    Calgary
    I think the more common configuration is to put both the resistor and capacitor in parallel. In this case, you can consider the effect of both components individually in order to understand what they'll do together.

    Adding a capacitor alone is the normal (simple) treble bypass circuit. As you know probably know, at 10 the capacitor is effectively eliminated out of the circuit. As you turn down the volume the capacitor allows more and more highs through. Some people like this, but some people find that now it gets too bright as you roll down the volume. In a sense this changes the taper of the pot as well. Most people don't think of it this way, but hey, the guitar is now louder at 8 than it was before due to all those highs getting through - to me that's changing the taper.

    If you were to add a resistor alone it allows all frequencies through. So as you turn down the volume it gets quieter, but not as quickly as it did before, since some signal can now pass through the resistor. Unlike the capacitor alone, the resistor alone is allowing the full frequency range to pass through.

    A finer point of this setup is that you will now have a variable resonant frequency on your pickup. This effect will be pretty subtle I think, but it is a part of the equation. At 10 your pickup will see an impedance of 250k (standard fender impedance). As you roll down that added resistor will be in parallel with part of the pot, lowering the impedance seen by the pickup and shifting the resonant frequency of the pickup to a lower frequency. You can pick the verbiage you prefer, but people generally call this either darker or muddier. I'd suggest ignoring this finer point for the moment, so:

    ... with the resistor alone your guitar *largely* behaves as it always had - turn it down and the guitar gets quieter and you start to lose the high end. So all that has happened is you've changed the taper on your pot a bit; I have experimented and I highly doubt anyone can hear the difference for the normally suggested values of resistance for R/C treble bypass.

    Add both those effects together and you get (what some people would say) is the ideal scenario: turn the volume down and the tone stays almost perfectly the same throughout the whole range of the volume pot. I spent hours experimenting one night with a bag of ceramic caps and resistors and with alligator clips hanging out of my guitar and I thought I achieved this effect precisely.

    In my usual long-drawn-out fashion, here's a post that describes the effect of resistor configurations on pots:
    http://www.tdpri.com/threads/graphs...-wiring-options-for-pots.816458/#post-8266175

    .. and then there's this guy who makes me look concise:
    http://guitarnuts2.proboards.com/thread/5317/treble-bleed-circuit
    (Great work by this guy)
     
    jrblue and muudcat like this.

  9. schmee

    schmee Friend of Leo's

    Jun 2, 2003
    northwest
    I tried some Treble Bleed schemes on my G3161 today. I normally dont like them, but for the way I use this guitar I would like to have the tone stay the same up and down the volume dial. I wasn't very successful:
    Kinman style: I didnt have the 130k resistor so tried a 150k. Frankly, I hear very little difference than with no treble bleed. Still a big treble jump when you dime the volume.
    Duncan Style: maybe a touch better than Kinman but still not a solution to tone change with volume change. Still a big treble jump when you dime the volume. I tried this right after getting the guitar though and not today. Maybe I need to revisit.
    Simple: Well, I like it better I think, but still doesnt solve the problem. Still a big treble jump when you dime the volume. But it seems the tone works smoother rather than with a fast jump in tone.

    I'm really surprised at my results. I dont think I've done anything wrong, pretty simple, it goes across the two lugs with wires on the Volume pot and not to the lug that is grounded. Maybe I need to analyze the Gretsch circuit on the 3161, it's just a volume and tone though. I've done the Duncan style on Teles and Strats and it seemed to work.



    [​IMG]
     

  10. dan40

    dan40 Tele-Holic

    924
    Aug 19, 2015
    Richmond Va
    I have had good results with using a smaller cap (200-300pf) without the resistor. I do notice that I loose a bit of the low end the further I turn the pot down though.
     

  11. The Ballzz

    The Ballzz Tele-Afflicted

    Age:
    63
    Apr 11, 2016
    Las Vegas, NV
    Another one to add to the list. This is the one used on the American Professional Teles and it works pretty darned well:



    AM PRO Treble Bleed.jpg


    Personally, I don't often see the need for a treble bleed on a regular style Tele, as that treble roll-off achieved when turning the volume down can be kind useful. On the other hand, with the weaker pickups on a standard type Strat, a good treble bleed is a Godsend!

    Just Sayin'
    Gene
     

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