Treble Bleed off mod for PRS Custom 22, Help

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by NOVA70, Sep 13, 2004.


  1. NOVA70

    NOVA70 Supporting Member

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    Hi,
    I just got a new PRS Custom 22 Artist that I would like to install a treble bleed off mod. I noticed that there is a capicitor on the volume control already. It has the 5 way rotary switch. I tried installing an 100 ohm resistor but I found it to be to bright. Does anyone know the value of the cap PRS installs or have any recommendations on how to do this?
    Thanks,
    Pat
     
  2. Clorenzo

    Clorenzo Member

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    As you said PRSs already have a treble bleed circuit, consisting on a single 180 pF cap accross the in and out lugs of the volume pot. Another typical circuit is a 150 kOhm and a 680 pF cap in parallel.

    The single cap moves the pickup resonant peak up in frequency as you turn the volume down, so not only does it prevent the usual treble roll-off, but also gives a different flavour (more single-coilish) to the pickup tone.

    The cap + resistor basically keeps the frequency response constant so the tone doesn't change noticeably.

    To see the effect of these two options or others you may want to try, you can use my volume and tone simulation spreadsheet available here:

    http://harryjguitar.com/voltone.xls

    Please read the first page for instructions. As explained, if you want to simulate just a capacitor in the bleed circuit, give the resistor a very high value such as 1000000 kOhm.
     
  3. NOVA70

    NOVA70 Supporting Member

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    Thanks for the help Carlos, I'll try the 1000000k resistor.
    regards,
    Pat
     
  4. Clorenzo

    Clorenzo Member

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    Sorry, I think I wasn't clear: The 1000000k resistor (that would be 1 Gigaohm! :eek: ) is just the value you have to enter in the spreadsheet to simulate that there's no resistor. You are not supposed to put an actual 1Gohm resistor accross the pot. I don't even think such a thing exists!
     
  5. NOVA70

    NOVA70 Supporting Member

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    Hi Carlos,
    I went to Radio Shack and got a 1 megohm resistor and a 10 megohm. Which should I use?
    Regards,
    Pat
     
  6. Clorenzo

    Clorenzo Member

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    Hi Pat,

    Let me try to explain this again: the cap that you have now in the volume pot IS a tone bleed circuit itself, you don't need to, and you shouldn't, add a resistor. If you like the way it works, just leave it like that.

    If you don't like it because it makes the sound too trebly when you turn down the volume but you still want to avoid the treble roll-off, you can remove the existing cap and replace it with a 680 pF cap and a 150 kOhm resistor in parallel, i.e. both soldered between the pot lugs where the current cap is soldered. This will give you a more linear effect.

    Hope this makes it clear,
     
  7. NOVA70

    NOVA70 Supporting Member

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    Yes it does , thank you. I have added This type of mod on 2 of my other PRS Single Cuts from a schematic I got from Seymor Duncan, but those guitars did not have any caps at all on the volumn control. What confused me was the exsising cap by PRS. I thought I could add the resistor and accomplish the same. I use tube amps (Komet) so the volume control is in use alot. I noticed with this guitar when you roll it down it tends to get bassey sounding that's why I thought I was missing something by not having a resistor on the volumn control. Thanks for your help.
    Pat
     
  8. Lewguitar

    Lewguitar Member

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    My 2002 PRS Custom 22 that I just traded an EJ Strat for yesterday also has the 180 pf cap across the volume control.

    I was wondering why the Dragon II pickups were so bright and clear so I took a look inside.

    I kind of like the sound of the guitar as is, but I might remove the cap or experiment with it eventually.

    I generally get tired of that extra sizzle...but for the time being it's kind of cool.
     

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