PAF Pro Dimarzio's TOO bright

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by rockon1, Oct 17, 2005.


  1. rockon1

    rockon1 Member

    Messages:
    11,456
    Joined:
    Aug 12, 2005
    Location:
    Stamford CT
    Ive got a beautiful Ibanez RGT3120 with PAF Pro pickups. Problem is that they are WAY bright for my tastes. Thinking of putting a capaciter right from input to ground to roll off some treble. Kind of like having the tone turned down 1/3 but without the pot in the circuit and the bother of making sure its where I want it every time I pick it up. Anybody have a rough idea of what value caps to use? Something in the ball park. Ill go to radioshack and get a few around the suggested size. TIA Bob
     
  2. EADGBE

    EADGBE Member

    Messages:
    12,384
    Joined:
    Sep 23, 2005
    I'm thinking a .01 mf.
     
  3. rockon1

    rockon1 Member

    Messages:
    11,456
    Joined:
    Aug 12, 2005
    Location:
    Stamford CT
    Thanks Ill give it a try along with a couple of others in that range. :)
     
  4. Clorenzo

    Clorenzo Member

    Messages:
    1,940
    Joined:
    Jun 16, 2004
    Location:
    Munich / Madrid
    That won't work. It won't be like a tone control turned down 1/3, it will be like a tone control on 0 with a smaller cap, which for a 0.01 uF cap means a very large midrange peak at about 600 Hz and a sharp rolloff down from there.

    The best way of taming the brightness of a pickup is actually a resistor, not a cap, between hot and ground. You can try several values between say 100k and 500k, or better still, install temporarily a 500 k pot (middle lug to hot and one of the other two lugs to ground), adjust to taste, measure it and then replace with a resistor with the right value.

    This spreadsheet:

    www.harryj.net/voltone.xls

    simulates the response of the volume and tone control circuit in an electric guitar. Read the instructions carefully and see what happens when you put just a cap (make the tone pot value = 0) compared to a resistor (make the tone cap = 10000000 and play with the value of the tone pot).
     
  5. rockon1

    rockon1 Member

    Messages:
    11,456
    Joined:
    Aug 12, 2005
    Location:
    Stamford CT
    Found a "weaker" cap than .01 in my junk bin. Seems to work nice. Just the highest frequecies cut off. Dont know the value. Guess I should try the resistor bleed off thing as the cap isnt the correct way to do it? :confused: BTW- Why does a cap cut off high frequencies in tone circuit and LOW frequencies in a speaker crossover? :confused:
     
  6. Clorenzo

    Clorenzo Member

    Messages:
    1,940
    Joined:
    Jun 16, 2004
    Location:
    Munich / Madrid
    Well, it's not that the cap isn't "correct", it depends what you want to do: the resistor lowers the resonant peak, which is usually the culprit of "trebliness", the cap actually increases its amplitude but lowers its frequency, so it changes more the overall character of the sound, but if you like the result, then it's perfectly ok to do it that way.

    In fact, the most accurate way of simulating a tone control turned down would be to put both a resistor and cap in series. Again, you can just find the position of the tone pot that you like, measure the pot at that position and then put a resistor of that value and a cap of the same value as the one in the tone circuit.

    As for the last question, think of a cap as a frequency dependent resistor: the higher the frequency, the lower the resistance. If you put it in parallel, as in the tone circuit of an electric guitar, its lower resistance at high frequencies means that those high frequencies are short-circuited to ground, so it's the lows and mids that go through. If you put it in series, as in the high pass section of a loudspeaker crossover, the high resistance at low frequencies means that only the highs go through.
     
  7. rockon1

    rockon1 Member

    Messages:
    11,456
    Joined:
    Aug 12, 2005
    Location:
    Stamford CT
    Thanks guys for the elucidation!:dude
     
  8. rockon1

    rockon1 Member

    Messages:
    11,456
    Joined:
    Aug 12, 2005
    Location:
    Stamford CT
    So I tried some 100K resistors . Hooked up 100,200,300 values but didnt like it. Sounded like it was robbing power from my pick up. Tried the different value resistor and caps in series and ended up back where I started- with what I figured out to be an .001 uF cap by itself. Anybody know what the rolloff on that is for curiosity sake?
     
  9. Clorenzo

    Clorenzo Member

    Messages:
    1,940
    Joined:
    Jun 16, 2004
    Location:
    Munich / Madrid
    For a typical, PAF type humbucker with 500k pots, this is what a 0.001 cap does to its frequency response (green with cap, blue without cap):

    [​IMG]

    As you can see, the resonant peak goes up in amplitude but down in frequency, from around 2.7 kHz to around 1.8 kHz.
     
  10. rockon1

    rockon1 Member

    Messages:
    11,456
    Joined:
    Aug 12, 2005
    Location:
    Stamford CT
    Thanks for the info. :) I couldnt open the spreadsheet you posted earlier... At any rate its way better but different pickups are still necessary for my tastes. I think Ill try some Dimarzio "Breeds". They are some of the warmest they make according to thier tone guide. The PAF Pro's are just to treble heavy. Even with the caps they sound a bit too thin for me. Its a bummer Ibanez choose them(of all the Dimarzios available)to use.
     

Share This Page