Bear with me a sec.
Grr.
So I've got a distortion pedal. I'd like to have 2 volume controls that you can switch between, kinda working like amp channels I guess. Set one quiet, set one loud and it's sort of an inbuilt boost (almost). I'll also be using a bi-color red/green LED which I've drawn up, but I can't figure out the easiest/safest way to make the 2 pots switch seamlessly without popping etc.
I started off with this:
(https://i.imgur.com/36BkkTJ.jpg)
But was informed that the volumes would be interactive.
Then I thought about a 3pdt. 2 poles for the switches, 1 pole for the LED (wiring not shown here sorry), like this:
(https://i.imgur.com/hepBjtN.jpg)
Then I heard from PedalPCB about just switching the outputs of lug 2 and leaving the inputs conjoined, like this using a DPDT (again the other pole is for the LEDs):
(https://i.imgur.com/H1RqX7x.jpg)
With the pin at the end there being the output pad.
The last method seems the easiest and most painless as one consideration mentioned with the middle method (switch poles before and after the pots) was a dropout as the switch is a break before make style so there'd be no anything for a split second before the connection sorts itself out.
This is going in a distortion pedal btw. Nothing amazingly fancy. Some clipping stages, then an active tone stack, then out through a 10uf cap into the volume pot as a regular voltage divider. I'm just trying to work out how to add a silent, instant switch where each pot is isolated from the other.
Any ideas?
If to use a foot switch to change from one pot to another then I would just do the secon design. It's not the most elegant, I'd call it the brute force method, but it will function exactly as you have said you want it to.
Won't there be a dropout of sound and/or a pop with that method?
I've used the 3rd one multiple times without pop issues.
Quote from: Arcane22 on December 03, 2020, 09:06:23 AM
Won't there be a dropout of sound and/or a pop with that method?
Maybe, I would think it would depend on the quality of the switch though.
I think you run the same risk with the third option as well. Assuming you are doing it with a mechanical switch then the that physical throw from one side to the other still has to happen. I think it's generally not noticeable with one pole switches, fewer moving parts less possible issues I guess, but it can still be there with a crappy single pole switch, I've experienced it.
Basically, whatever method you use just make sure to use a good quality switch.
3rd option will present the previous stage with an impedance of 50k instead of 100k, since 2 x 100k pots in parallel to ground = 50k. Depending on the output impedance of the previous stage, you might lose 1.5 dB or so, not enough to notice.
Aye I did wonder what the effect on volume would be, if any, given the resistance is now halved. But, I've got more than enough volume tk spare with this thing so hopefully nothing drastic will occur. And I can need up the pots to 250k to restore that value if I needed to.
Cheers for the help guys, I'll opt for the third option as it requires 6 lugs being wired rather than 9, and 9 doesn't seemingly offer any obvious benefit that justifies the pain in the hole.
Onwards and upwards.
Check out the schematic for Bean's Mysterioso. It does what you are talking about but also switches between two gain pots. Looks like he uses the third option.
So it does. I should have known there'd be something similar. If there was a Mount Rushmore of DIY pedal builders you know Brian would be on it.
One other option is to use a 4PDT switch and fully switch out all three lugs of each pot, while still utilizing the bicolour LED. Just throwing the idea into the ring.
Jacob
It can be done with a 3PDT abs keep the bicolour LED
https://www.diystompboxes.com/smfforum/index.php?topic=119886.0
Quote from: jkokura on December 05, 2020, 07:23:16 PM
One other option is to use a 4PDT switch and fully switch out all three lugs of each pot, while still utilizing the bicolour LED. Just throwing the idea into the ring.
Jacob
This is what I was going to recommend.