/ Register

  1. Win a Broadcaster or one of 3 Teles! The annual Supporting Member Giveaway is on. To enter Click Here. To see all the prizes and full details Click Here. To view the thread about the giveaway Click Here.

What is the function of this .02uf capacitor in tremolo of Princeton Reverb?

Discussion in 'Amp Tech Center' started by doug, Oct 21, 2020.

  1. Oct 21, 2020 #1
    doug

    doug TDPRI Member Silver Supporter

    Posts:
    48
    Joined:
    Apr 25, 2003
    Location:
    Boston,MA USA
    Just wondering what is the purpose of the .02uf capacitor I circled in red in the image I attached.

    Thanks.
     

    Attached Files:

    tubegeek likes this.
  2. Oct 21, 2020 #2
    Phrygian77

    Phrygian77 Friend of Leo's Gold Supporter

    Posts:
    2,469
    Joined:
    Apr 30, 2016
    Location:
    Crawfordville, FL
    Smoothing the output of the tremolo.
     
    D'tar likes this.
  3. Oct 21, 2020 #3
    tubegeek

    tubegeek Friend of Leo's

    Age:
    60
    Posts:
    3,882
    Joined:
    Jan 31, 2020
    Location:
    Brooklyn, NY
    ... by shunting high frequencies to ground and leaving low frequency oscillations to go through the larger (.1) cap to the intensity control. Filters out noise & any "spiky" frequencies in the tremolo oscillator.
     
    LudwigvonBirk and D'tar like this.
  4. Oct 21, 2020 #4
    D'tar

    D'tar Friend of Leo's

    Posts:
    3,167
    Joined:
    Jan 11, 2013
    Location:
    WNY
  5. Oct 21, 2020 #5
    Ten Over

    Ten Over Tele-Holic

    Posts:
    682
    Joined:
    May 13, 2015
    Location:
    Central California
    The .02uF cap in question and the 1M resistor that it is connected to form the high-cut portion of a bandpass filter. The .1uF cap and the 250K Intensity pot form the low-cut portion.

    When the high cut-off frequency gets close to the low cut-off frequency, the signal that passes becomes attenuated as compared to signals with the cut-off frequencies well spaced. The cut-off frequencies with the Princeton tremolo are very close, so the tremolo signal is attenuated in addition to having a limited bandwidth.
     
  6. Oct 22, 2020 #6
    doug

    doug TDPRI Member Silver Supporter

    Posts:
    48
    Joined:
    Apr 25, 2003
    Location:
    Boston,MA USA
    Thanks for all of your answers. I asked the question after reading the following in https://guitar.com/guides/diy-workshop/diy-workshop-rift-amp-mod-part-2/

    Between the 1M resistor and 0.1uF capacitor, there’s a 0.02uF capacitor that’s tied to ground. It’s not there in the brownface trem, and de-soldering one end of the capacitor seemed to give the Rift’s trem a stronger feel. I decided to remove it, but do so carefully because it will come in useful for the next stage.​

    While I supposed I could just lift one end to hear the results, I was wondering what downside might exist by removing the .02 capacitor.
     
  7. Oct 22, 2020 #7
    Ten Over

    Ten Over Tele-Holic

    Posts:
    682
    Joined:
    May 13, 2015
    Location:
    Central California
    See Reply #3.

    Sometimes the LFO will oscillate at higher than tremolo frequencies even when turned off by the footswitch. The .02uF cap will shunt those frequencies to ground so that they don't show up at your bias.

    You can get a little more intensity by removing the .02uF cap, but there are other ways to do it without losing one of the functions of the .02uF cap. Those guys at Fender actually knew what they were doing and they wouldn't have put an additional component in an amplifier unless they had a good reason. But go ahead and try it. That's what the guy that wrote the article does.
     
IMPORTANT: Treat everyone here with respect, no matter how difficult!
No sex, drug, political, religion or hate discussion permitted here.