Author Topic: stomp box switch pop question  (Read 3008 times)

pjohns0

  • Diode Destroyer
  • *
  • Posts: 2
    • View Profile
stomp box switch pop question
« on: October 07, 2011, 02:58:27 PM »
Hello.
My ThunderPuss clean boost pops when turned on.  I've read the Geofex article about how to fix the pop and think I understand how to apply it, but I had a broader question about this fix on other circuits.

The Geofex article states:  "For mechanical switches, put a 100K to 4.7M (exact value does not matter) resistor from the "outboard" end of both the input and output capacitors to ground. This keeps the ends of the capacitors pulled to the right voltage all the time, and cures the leakage problem. No capacitor clicks."

OK.  So on the ThunderPuss, I take that to mean place the resistor on the output end of both C1 and C4.  Correct me if I'm wrong.

Now, for other circuits, it's my understanding that the input and output caps may not always be the first capacitor and the last capacitor in the circuit, correct?  For example, sometimes there is a very high value cap to filter RF that is the first cap in the circuit.

So how does one determine exactly what cap is the input and output capacitor in all circuits?

I really appreciate the help.  I really, really like the ThunderPuss.

bigmufffuzzwizz

  • Electron Doctor
  • *****
  • Posts: 2626
  • Magic S.
    • View Profile
    • Magic Pedals
Re: stomp box switch pop question
« Reply #1 on: October 08, 2011, 11:40:50 AM »
Yes the Input/Output caps on the Thunderpuss are labeled C1 and C4. I've seen other circuits that don't necessarily use that set-up, but a lot of them do, especially fuzz/distortion. I don't know about a "rule" to determining those 2 caps when its designed different, I don't think I've ever heard mention of that but I could be wrong.
Owner and operator of Magic Pedals

stecykmi

  • Electron Doctor
  • *****
  • Posts: 1021
  • Misha
    • View Profile
Re: stomp box switch pop question
« Reply #2 on: October 09, 2011, 12:38:36 AM »
first off, the input or cap will never go to ground as may be the case with some input filter caps. C1 on the PepperSpray project in an example of an input filter cap. It's quite small so it probably filters frequencies off over 6kHz or 7kHz.

second, many many circuits use a capacitor to block DC bias voltage of an opamp or transistor. these are nearly always in series with the base (on BJTs) or gate (on MOSFETS or JFETS). This is like C2 also on the PeppperSpray project.

melody_guitar

  • Diode Destroyer
  • *
  • Posts: 5
    • View Profile
Re: stomp box switch pop question
« Reply #3 on: November 24, 2011, 03:51:44 AM »
is it the "pulldown resistor" that we are talking??..the switch popping might happen because of the sudden flow of the current to the circuit when switching..

TNblueshawk

  • Electron Doctor
  • *****
  • Posts: 1478
    • View Profile
Re: stomp box switch pop question
« Reply #4 on: November 24, 2011, 07:46:24 AM »
This is one of my go to threads at times. Scroll down, unless it come up right there, and RG Keen comments on it. There is another longer thread on this that he has but I can't locate it at the moment.

http://www.diystompboxes.com/wiki/index.php?title=Frequently_Asked_Questions_(DIY_FAQ)

Here is another good one

http://www.freestompboxes.org/viewtopic.php?t=13053
« Last Edit: November 24, 2011, 07:53:50 AM by TNblueshawk »
John