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Post by flateric on Jan 21, 2010 18:41:10 GMT -5
Having converted a few homebrew pedals to 9vdc to rig onto my gigging pedalboard I find the distortion pedals in particular pop really loudly when i turn them on/off. I think theres a simple remedy involving a 100uf electrolytic cap across input abd ground to eliminate this but wanted to check with the gurus here first....  |
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Post by ashcatlt on Jan 21, 2010 19:42:20 GMT -5
This just started after you converted them? What did you change?
It was my understanding that these pops are often caused by the AC-coupling caps on either end of the circuit which store a voltage when disconnected and then discharge rapidly when connected. This is usually fixed with a largish pull-down resistor (to ground) between said cap and the switch.
Sometimes it can also be more or less "mechanical" noise called bouncing from the switch itself. which can be helped with with a cap-to-ground type LPF. Keep in mind that the frequencies removed from the pop via this route will also be removed from your signal. You can probably get rid of the "clicky" part without much trouble, but seems like you'd be left with the "thump" part.
'Course, I've never tried it either way, so...
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Post by JohnH on Jan 21, 2010 20:24:28 GMT -5
I get the same pops with my OD circuits, and I do two things to fix them:
A large pull down resistor to ground, as Ash describes, on the input (really large, say 3.3M or greater), and on the output (can be smaller, about 1M is good)
But there is also a pop induced by switching the LED, which for my circuits, usually uses much more power than the circuit itself. A 100uF or greater cap across the power supply can help, but it works best if this cap is put across the + and - on the board, with a resistor from board + to the power supply+ , calculated to drop about 1/4V. Then I get the LED power directly from the supply, before this resistor. This way, power transients causes by switching the LED are separated from the circuit supply by the resistor, and smoothed by the cap.
John
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Post by flateric on Feb 1, 2010 7:05:17 GMT -5
3.3M pull down resistor on the input solved this one for me, thanks guys!
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