Silent Momentary switch with Pot

[jghfslk]

I'm hoping to be able to switch between two potentiometer settings with a momentary footswitch.  The footswitch would still function like a momentary switch. I will need it to be either a SPDT or DPDT.  A SPST won't work for what I'm going for.  Would something like a coda relay bypass work in this application?  My goal is to have two different resistance settings, each that you can dial in with a pot, and have the ability to go from one normal setting to the other setting while the footswitch is held down.  I have tried it with a DPDT momentary footswitch but it clicked waaaay to loud to be useable.

Any help is appreciated!

[sonnyboy27]

You could build something framed around tge coda bypass. You'd need to tweak the debounce portion of the code to make it a momentary switch rather than latching I believe. But I think there's a variable you can set for just that kind of thing.

[Stomptown]

I would take a look at the TH Customs Uber switch to see if that might work for you.  It's a relay bypass system with mute-while-switching feature which should silence any clicks.

[jghfslk]

I placed an order for the Uber switch.  Thanks for the suggestions!

[WormBoy]

Are you looking for a momentary switch to switch between two settings when you tap it, or a momentary switch that only goes to the other setting as long as you hold the switch down? Since you have tried a momentary DPDT, I would guess the second, but the Uber falls in the first category.

[Boba7]

Also you may want to have a look at mictester relay bypass, its very simple to build and if you used a momentary, it'll be momentary switching. And you have a dpdt relay to switch resistors.

What's the switched pots functions by the way?

[jghfslk]

I'm looking to switch to the other setting only when the switch is held down.

My plan is to use this with a pt2399 delay.  I would use two time pots and wire them to the momentary stomp to switch from one time to another when the stomp is pressed down.  Would the mictester be able to serve this function?

[WormBoy]

I'm looking to switch to the other setting only when the switch is held down.

In that case, I would use the simplest solution, namely a momentary switch (SPDT would suffice). There should not be any clicks or other noise when switching between pots unless the switch is crappy. I don't see how a relay would be less noisy than a manual switch (and I can easily see how it will be more noisy), unless you have a mute in the circuit (which can rapidly become pretty annoying IMO).

[jghfslk]

The switch I tried it with is was a DPDT momentary that clicks when pressing it.  I could not find any soft touch SPDT or DPDT momentary footswitches.  Anything else I can try with the switch i have to make it less noisey when switching between pots?

[WormBoy]

It would be good to figure out why you get switching noise. The pot for delay time is not in the audio path ... you might get some funny echos when switching, but I don't see how you can get noise at the output (that might very well be my limited knowledge  ). If it were my build, I would check how I wired it, try another switch, and if nothing helps try some solution with optocouplers.

[Boba7]

Totally agree with WarmBoy

But are you talking of the mechanical noise of the switch, or noise that you can hear through the amp?

Cause as WormBoy says, you shouldn't hear any noise switching from a time pot to another. If you're talking of external mechanical noise, then I'm pretty sure Mictester relay switching will help.

[jghfslk]

I tried it again using a DPDT momentary switch with a Deathklaw build.  I'll make a video of the noise but unfortunately it won't be for a couple of weeks as I use my brothers camera and I won't see him until then.  What I don't get is that I can have the delays set to the same time, or as close as I can get, and when pressing the switch I get the loud noise.  I was thinking that when the pots are close to the same resistance it would behave like a led/ldr modulation but you would have control of the depth with the second time pot and it would only modulate when pressing the switch down.  If I had to take a guess it would be that there is just a tiny delay when switching from one resistance to another which results in the chip acting crazy.  Could this be causing the noise?

[WormBoy]

I have built two PT2399 with switchable delay times (using a toggle switch), and neither is making any noise to speak of (apart from some modulation of the repeats immediately after switching). Are you switching the ground side of the pot (that seems safest to me)? Are you switching an indicator LED with the same switch (LEDs might induce popping under some conditions)? Have you tried another momentary switch (this one might be dodgy)?

Edit: just tried my switchable pt2399 delay to make sure. When not playing, the switch is completely noiseless. However, when there is sound, I get some weird noises when switching; some sort of short rumble (lower pitch than the one played) when switching to longer delay settings, and some higher-pitched rumble/tone when switching to shorter delays. Is that what you're experiencing?

[jghfslk]

A rumble would be a great way to describe it.  Do you still get the noise if your delays are set to the same speed?
  The pitch changes are exactly what I am going for.  My hope is that I can set the delay times so that when engaging the switch my repeats shift up or down to a specific pitch interval.  For example if I set one delay to 200ms and the one other to 100ms the repeats would shift an octave.  I get the noise even when no signal is going in to the circuit and I press the switch.  I am not using an LED indicator and have tried at least two different switches but both had the noise.

[WormBoy]

When both are set to the same delay time, I also get a modulation of the repeats, and sometimes even a bit of a pop. When there is no sound playing, it is dead quiet. So it could well be that the PT2399 does not like this kind of sudden switching of the resistance when it is working. If you do want to switch between delay times while playing, I guess you need to avoid the sudden switching of a footswitch or toggle, and go for something optical. Maybe the LERA could be useful: http://www.geofex.com/article_folders/lera/lera.htm. You could tune the speed of the transitions with the trim pot(s) and/or the value of the cap ... It would take a bit of experimentation though.

Edit: you can also take a look at the 1776 Multiplex Echo machine that uses an optocoupler to slowly change the value of the delay time resistor, or the 'splode' in the MB Mandroid. Would require some tweaking to get it to morph to a well-defined second value at the required speed. Furthermore, I was thinking that you could also replace the delay pot entirely by an LDR (with very low on-resistance), and switch between two voltage levels (using two pots set up as voltage dividers, probably with an offset as the off-resistance of LDR is usually too high). You need a CLR and LED, and can slow down the response with an additional cap to ground. That way, there is always some resistance for the chip, and no sudden changes in that resistance. Hmm, this could make a nifty mod for all PT2399 delays ... .