Anti pop resistor for gain stages?

david1991ross · August 17, 2020, 08:13:52 AM

When I use a DPDT on-on-on switch I noticed that I'm getting a popping sound when I try to go from soft clipping to hard clipping. I was wondering if I could place an resistor and possibly a capacitor somewhere which would remove the popping noise that I'm getting from the switch. Any ideas? Here is the schematic I'm looking at, I included a visual of the DPDT on-on-on switching layout.

merlinb · August 17, 2020, 08:24:40 AM

You need to keep C8 charged up to the same voltage as everything else even when it's not selected. Try connecting a large resistance (e.g. 1Meg) from the wiper of the switch to R8.

david1991ross · August 17, 2020, 08:37:56 AM

So something like this?

merlinb · August 17, 2020, 08:38:14 AM

Yes exactly

david1991ross · August 17, 2020, 08:45:08 AM

So in your estimation this will eliminate the popping completely? Or just partially? Also, after doing some research I've seen people suggest putting a capacitor in line the the resistor, is this necessary? Also, would it be necessary to also put a 1meg resistor on pin 5 give that it's switching from open to diodes?

teemuk · August 17, 2020, 09:35:24 AM

You probably need a steady reference for C9 and C10 as well. (Just put a high-ish resistance in parallel to those "hard clipping" diodes. Naturally do not switch it on or off while you switch diodes. Just keep solid connection to GND).

r080 · August 17, 2020, 10:21:46 AM

I am just curious - with this circuit, are you getting much of a difference in character/sound between hard clipping only and hard clipping plus soft clipping. If not, you might be able to simplify it. Although, it looks like you are giving it more bass in the hard clipping configuration, so maybe that switch is an important part.

david1991ross · August 17, 2020, 10:26:19 AM

Quote from: r080 on August 17, 2020, 10:21:46 AM
I am just curious - with this circuit, are you getting much of a difference in character/sound between hard clipping only and hard clipping plus soft clipping. If not, you might be able to simplify it. Although, it looks like you are giving it more bass in the hard clipping configuration, so maybe that switch is an important part.

I will experiment with different hard clipping diodes, maybe some germaniums similar to a Distortion +. This will likely alter the sound between soft and hard clipping to where it's worthwhile having the switch.

david1991ross · August 17, 2020, 10:36:24 AM

Quote from: teemuk on August 17, 2020, 09:35:24 AM
You probably need a steady reference for C9 and C10 as well. (Just put a high-ish resistance in parallel to those "hard clipping" diodes. Naturally do not switch it on or off while you switch diodes. Just keep solid connection to GND).

Would you suggest this:

r080 · August 17, 2020, 10:43:22 AM

LEDs in the soft clipping stage might also do the trick. If your hard clipping diodes dominate the effect when turned on, there should be a way to keep the soft clipping diodes on when in the hard clipping mode, possibly reducing the likelihood of popping when switching between modes.

Steben · August 17, 2020, 12:46:11 PM

Quote from: r080 on August 17, 2020, 10:43:22 AM
LEDs in the soft clipping stage might also do the trick. If your hard clipping diodes dominate the effect when turned on, there should be a way to keep the soft clipping diodes on when in the hard clipping mode, possibly reducing the likelihood of popping when switching between modes.

Yes, but soft clipping "on" means the opamp will probably not clip. This is important in overal sound, even with diodes to GND. It is a kinda "gentler" way of designing distortion devices. (used in ODR-1 a.o. as recently mentioned)
A Rat for instance sounds different big time with such soft clippers.

Hard clippers in inverting feedback loop don't have opamp clipping (at least with normal signals and supply voltages).

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Anti pop resistor for gain stages?