How to add SPST switch to delay pedal

[sethwitz]

Hi all, first post here! I tried my best to research this question (checked Tagboard Effects, Free Stomp Boxes, Reddit, etc.) but I haven't come across any resources that have fully cleared up my confusion on this.

Tl;dr is: I'm hoping someone can help me learn how to add a momentary switch to a delay pedal so that I can immediately shorten the delay time to create a pitch shift effect.

Full story time: The inspiration for this idea is twofold. First, I came across this video some number of years ago:

Ever since seeing this video, I have been DESPERATE to learn how to create a similar delay pedal featured on this guy's board because I LOVE the momentary switch that creates the pitch shift effect. The second bit of inspiration for this is, of course, the DOD Rubberneck. (The crazy thing is I already own the Rubberneck, but of course I won't be satisfied til I learn how to build this thing.)

My best (and very uneducated) guess is that I could send a wire from lug 1 of the Delay/Time potentiometer to lug 1 of an SPST switch and then connect lug 2 of the SPST to lug 3 of the Delay/Time potentiometer. Maybe a trimpot goes somewhere in the middle?

Any advice would be super appreciated—thank you!

 

[Bricksnbeatles]

depends on the particular delay circuit and whether the delay time increases or decreases with maximum resistance of the pot. Also depends on how much you want to to decrease the delay time. Should be pretty easy though in most applications. Can you share with us which delay circuit you’d like to do this in? I could take a look at the schematic and point you in the right direction when I get a chance (or someone else will beat me to it)

 

[sethwitz]

Wow, thanks for such a quick reply! I was thinking of making this circuit (EQD Space Spiral) and adding this momentary switch. Or perhaps the Keeley Magnetic Echo.

 

[sethwitz]

Hi there @Bricksnbeatles, any chance this would be doable with the circuits above? If not, no worries!

 

[jwin615]

May need to experiment with the pot value. Not sure there but guessing 100k-250k.
That *should* give you a ramp up or down depending on pot position.
Use a normaly open footswitch. Carling is a good brand.

Edit.
Could start with a B1M pot and see if there is any usability in the last half of the pot. If not, 500k.
If it's only usable in the first 1/4, 25pk. If only the first bit, 100k.
Can add series resistance to the pot as well. I'd probably add at least a 500 ohm resistor to be safe.

 

[sethwitz]

Thank you for adding this, I think I get it!

So in this configuration, the setting of that (100k-250k) potentiometer would determine how quickly or slowly it ramps the rate up or down?

And does the SPST go between lug 3 of that pot you've drawn and the stripboard?

 

[jwin615]

Note, the "chaos pot" for lack of better term, will have a different behavior depending on the setting of the delay time pot.

This is a semi "tunable" version.
You can also jumper the pot via footswitch with a fixed resistance. That's the other option and will always sound the same, regardless of delay time pot position.

 

[jwin615]

Thank you for adding this, I think I get it!

So in this configuration, the setting of that (100k-250k) potentiometer would determine how quickly or slowly it ramps the rate up or down?

And does the SPST go between lug 3 of that pot you've drawn and the stripboard?

I'd put it between lug 1 and the strip board. Mirror the other pot so it operates in the same direction.
You are basically manipulating the resistance of the original time pot by adding a parallel resistance.
So as you change it, it alters the overall resistance seen by the circuit.
I would do this on a breadboard first.
Just run 2 wires over to it from the stripboard. Could use alligator clips as well.
Also, disregard the adding a resistor comment. That already exists in the circuit.

 

[jwin615]

And yes, the setting would determine the change. Same as yanking the time pot quickly.
If you just want a single setting, you need to put a momentary footswitch (dpdt) between lug 1 of the time pot and the board and lug 23 and the board with a resistor in the momentary spot. So that you are switching between either the pot or the fixed resistors in place of the pot.

 

[sethwitz]

Double thank you, I'm very excited to try this out! Good call on breadboarding it first.

 

[jwin615]

No prob. Hope you find what you're after and maybe learn a bit along the way.
I'm pretty sure this concept would apply to any/most pt2399 delay
You could also run this circuit off of the time put.
As long as you're switching in/out a resistance to the pot(which is being used as a variable resistor), same difference. That may be a cleaner solution for wiring.