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THC 5-band EQ/Fatpants Jr 2 in 1 and Lumen Bypass ... with switch pop!

Started by brucer, March 10, 2017, 07:45:33 AM

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brucer

So, I built a pedal as a thank-you gist for a friend (who likes to use an EQ as a boost).  It's a 2-in-1 with the following signal chain:

Input > GC Lumen/THC 5-band EQ > GC Lumen/MB Fatpants Jr 2:1 > Output

Power goes from the DC jack to the EQ's Lumen board, then from there to the Fatpants Jr's Lumen board.

The Fatpants Lr works great on it's own ... as long as the EQ is off: silent switching and low noise, high output boost.

The EQ is the spanner in the works: the EQ knobs do what they're supposed to, BUT:

     1. horrendous stomp switch pop on when turning the EQ on/off; AND, worse yet,
     2. horrendous switch pop from the Fatpants Jr when the EQ is already on.

Has anyone run into switch pop with this or other EQ circuits even when using an optical bypass?  Can anyone suggest a possible fix?

I'd love to gift this pedal to my friend, but it's not usable as-is.

Thomas_H

Hi, check the output cap of the 5 band eq. It may be leaking dc.
You may waht to add a pull-down resistor at the output of the eq.

Best
Thomas
DIY-PCBs and projects:

brucer

Thanks Thomas.  I really appreciate your response.  Sorry for the newbie questions, but ...
- Is checking for DC leakage at the output cap simply checking for any DC on the negative side of C3? 
- If there is DC leakage at the output cap, then do I replace it and hope for the best or is there a way to test caps for leakage beforehand?
- Can you please let me know exactly where to attach each end of the pull-down resistor at the output of the EQ?  Is it simply from the negative side of C3 to ground?

Again, thanks.  I'd definitely appreciate any suggestions you might have.  Bruce.