Deep Blue Delay Switch Pop

[Ghode]

Hi! I recently bought a deep blue delay (DIY) and I liked the sound of it but I also like the option of having darker repeats so I modded it to being abble of switching parallel capacitors to lower the frequency of the low pass filter at c11, like in the image.

The thing is, when switching from 2 to 1 or 3 (not backwards) it pops.

How can I fix this? Should the switch connect the caps to ground instead of connecting them to C11? Any other trick?

I'll leave the schematic.



Thnx!

[Mark Hammer]

Capacitors do not like having a "free end", with no way to drain off.  The pop you hear is all the stored charge suddenly rushing out when an opportunity to drain finally arrives.

A strategy I've had good success with is to place a high-value resistance (1M is usually good) in series with the cap so that the cap is effectively out of circuit, but still has a means to drain off, since that resistor is connected both to the cap and to somewhere else.  Switching the cap "on" simply consists of using a toggle or whatever to bridge that resistor so that the cap is now directly tied to wherever you had wanted it to go.

Think of it this way.  Right now, you have a switch that selects between zero ohms (cap connected) and infinite resistance (switch open).  The new arrangement will select between zero ohms and high resistance; enough to make the pop go away.

[PRR]

[Ghode]

Thanks a lot for the answers!

What I understood from Mark is to put a resistance in series with the cap (from C11/R13 to GND), but in the schem of PRR they are in "series" with the caps (different arrengements depending on the position of the switch). Wouldn't that setup form another low pass filter with a lower frequency?

[PRR]

Yes, not the same.

Both ways will work. In this circuit, mostly 10K/22K resistors, 10Megs hanging-on won't affect the intended action, but will keep the caps at the right voltage when not in use.

My way *may* be a bit easier to wire. Maybe not. May depend on the situation.

[Ghode]

Yep, that's right, much easier to wire, directly to the switch.

Will try it and I report how it goes!