Pedal causes other pedals to Pop

Started by 12StringStratMaker, July 21, 2008, 11:50:31 PM

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12StringStratMaker

I recently did an online trade for a pedal that appears to be wired as true bypass.  When I turn it on and off, there isn't too much of a pop.  However, when I turn other true bypass pedals on in my chain while this pedal is in the chain, there is a HUGE pop noise. 

It happens whether the pedal is on or off and whether powered by the same adapter/T-rex fuel tank or off 9v battery.  I have made sure that it is not the cables.
Is there some sort of grounding problem?  How is this causing the other pedals to do this?

Cardboard Tube Samurai


axg20202

Sounds to me like there is a wiring issue that's putting DC into the signal path.......dunno though...

petemoore

I recently did an online trade for a pedal that appears to be wired as true bypass.
  Why?
   When I turn it on and off, there isn't too much of a pop.
   However, when I turn other true bypass pedals on in my chain while this pedal is in the chain, there is a HUGE pop noise.  
  How many of the relevant input and output capacitors actually have pulldown resistors on them ?
It happens whether the pedal is on or off and whether powered by the same adapter/T-rex fuel tank or off 9v battery.
  Try measuring the DC on the jacktips with nothing plugged in, you may have to trick the input jack to power the circuit.
  I have made sure that it is not the cables.
Is there some sort of grounding problem?
  Yes, there is always some sort of grounding problem, but it's really only a problem if it gets caught. Ie...probably not a grounding problem, does the chain induce hum ?
  How is this causing the other pedals to do this?
  DC charge would be my guess, somehow, DC is leaking into the capacitor of the other effect, prehaps the charge current is faster than whatever it has for a 'drainpipe' [pulldown resistor or other], which is intended to keep that capacitor discharged at 0.0v = Gnd.
  First I'd check for pulldowns on the effect which has the switch popping problem, maybe try bringing them to a lower value, greater than say > 1 meg.
  Then I'd check for DC presence on the signal path, just past the DC blocker caps, on the 'whatever', box you bought.
Convention creates following, following creates convention.

analogmike

Does the pedal have an LED?

Disconnect the LED power wire from the switch, does that fix it?
DIY has unpleasant realities, such as that an operating soldering iron has two ends differing markedly in the degree of comfort with which they can be grasped. - J. Smith

mike  ~^v^~ aNaLoG.MaN ~^v^~   vintage guitar effects

http://www.analogman.com

mdaudet

I had the same problem you have.

I had the same behaviour with other TBP pedals with a IC buffer from GGG. The end of the circuit was open, no pulldown or pot R on there, so I put a "pull down" about 10K and the problem dissapeared.

My guess (as petemoore) is you have DC Charge. There must be an output capacitor without a pulldown R, so I assume your traded effect doesn't have a master level pot at the output (or maybe the TBP is bad performed)

First, check is there is any DC on the line.
If you have DC lectures, try adding a pulldown resistor +/- 1M at the end of the output cap to ground. That would solve your problem, at least it solved mine in the past.



Good luck.