silismile: what does R5 (1m ohm res.) do? Some designs don't have it

[paulbarrette]

Hi all,
I am wondering what the 1m ohm res (R5). does in the silismile circuit:

https://docs.pedalpcb.com/project/SiliSmile-PedalPCB.pdf

I have seen a few designs that don't use it, but I think all pedalpcb boards do. A lot of designs don't use the 47uf cap on the power rail. That one make sense to me as a filter.

thanks
Pb

 

[JamieJ]

That is a pull down resistor that try’s to stop popping sounds when switch is engaged.

 

[paulbarrette]

Thanks for the explanation!

Pb

 

[cdwillis]

Sometimes the input capacitor can hold some charge and when you engage the pedal that built up charge causes a popping noise. With the 1m resistor it always has a path to ground to eventually bleed off.

If you use the default 3pdt wiring from the Pedalpcb docs, the input of the circuit is grounded when bypassed so the 1m isn't really needed. Plus some circuits have a resistor to ground that connects to the input cap (like a big muff for example), but they still have the pulldown resistor on there as an option.