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Capacitor Help

Discussion in 'Just Pickups' started by Trow, Jul 29, 2019.

  1. Trow

    Trow Tele-Holic

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    Hey guys, I need help determining what capacitor I need. I recently wired a good buddy’s acoustic with two piezo’s in series stuck on the soundboard close to under the bridge running to an end pin jack. It sounds great, but the highs are a little much. I was hoping a putting a capacitor in there would help it out some. My problem is that I don’t know what value to use. What would filter out a lot of the highs and maybe some mids?
     
  2. Dacious

    Dacious Poster Extraordinaire

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    I'd be inclined to try from .047mfd down to .022. the .047 would still let some of the percussive sound through and probably be about right.
     
  3. Derek Kiernan

    Derek Kiernan Friend of Leo's

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    We can't really make a suggestion without knowing what products you're working with. The capacitor value would be entirely dependent on the inductance of the system. If there a tone control as part of a circuit on the guitar?
     
  4. Zepfan

    Zepfan Doctor of Teleocity Gold Supporter

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    Piezopassivetonewiring (1).jpg I've heard that this works well. I haven't installed any round piezo's in a guitar for awhile so I haven't been able to test it. The 1meg pots are usually recommended due to the high impedance.
     
  5. Teleterr

    Teleterr Friend of Leo's

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    Isn t that set up as a high pass filter ?
     
  6. Trow

    Trow Tele-Holic

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    8948781B-E81C-425B-96BB-35FF04E5005F.jpeg I wired it straight to the jack, just Piezo's and wires. I attached the wiring diagram I used.
     

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  7. Antigua Tele

    Antigua Tele Friend of Leo's

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    Buy a box of assorted caps and aligator clips on Amazon, then expose the connections of the guitar cable at the end pin, and using the aligator clips, test various caps across the cable connection until you find a value that works to your liking, and solder that across the end pin jack.
     
  8. Derek Kiernan

    Derek Kiernan Friend of Leo's

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    What's the pickup you're using?
     
  9. tele_savales

    tele_savales Tele-Holic Platinum Supporter

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    I just threw 25 bucks down on a capacitor substitution box and the thing is awesome. Paid for itself in one weekend. Real handy.
     
  10. rigatele

    rigatele Tele-Afflicted

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    Capacitors won't work the same way with a piezo as with a magnetic pickup, because they are themselves capacitive in nature. If you put one in parallel with the piezo, you are creating a capacitive voltage divider that will mostly change the gain, instead of the tone. Here is a Spice simulation showing the response with different parallel capacitive loads:
    piezo_response.png
    The response is mostly flat, and an increase in load capacitance lowers the low frequency cutoff, and decreases the gain.
     
  11. Zepfan

    Zepfan Doctor of Teleocity Gold Supporter

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    I just realized that you(the OP) said that you wired the 2 piezo in series. You should never wire 2 piezo in series because you just made the impedance problem twice as bad. Wire them in parallel and it will reduce the impedance problem and work better with passive electronics.
     
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