TRS jacks for adding expression options

[Hollytron]

Hi,

I would like to add an expression jack to a DOD fx 90 delay pedal to control the mix pot. I recently purchased some TRS jacks but they are not switched jacks and upon doing a bit more research it looks like switched jacks are usually called for in such an endeavor.

I do wonder if the regular jacks would still work but perhaps only if there is a trs plug in the jack.

Any illumination on this subject is greatly appreciated

 

[Robert]

You need a switched jack to make the pot in the pedal active when nothing is plugged into the TRS jack.

Depending on where it is in the circuit, you might (will most likely) need an insulated jack.


You need a switched TRS jack to make the pot in the pedal active again when nothing is plugged into the expression jack.

If you absolutely must use a regular non-switched TRS jack you have two options:

1) Disconnect the pot in the pedal entirely. It will no longer function at all and the pedal won't function properly without an expression pedal connected.

2) Connect the the jack in parallel with the existing pot. The knob on the pedal and the expression jack will simultaneously be active (and be highly interactive with each other), and the range of the expression control might be affected, but the pedal will still work as normal without an expression pedal.

 

[Hollytron]

2) Connect the the jack in parallel with the existing pot. The knob on the pedal and the expression jack will simultaneously be active (and be highly interactive with each other), and the range of the expression control might be affected, but the pedal will still work as normal without an expression pedal.

Thanks for the very informative reply. I am running a Moog expression pedal and do not have to use the non TRS switched jack but I am intrigued by the idea above about running the jack in parallel with the pot. The Moog pedal has two modes (normal and standard) as well as a knob on the side that in my experience running it with a glitchy boss dd7 changes the amount of the in this case mix getting through. The important thing for me is to be able to use the pedal to go completly dry and then swell in the wet signal.

I can probably just try the parallel idea with alligator clips but I wonder if you have any further insight on this set up. Thanks!

 

[jwin615]

Thanks for the very informative reply. I am running a Moog expression pedal and do not have to use the non TRS switched jack but I am intrigued by the idea above about running the jack in parallel with the pot. The Moog pedal has two modes (normal and standard) as well as a knob on the side that in my experience running it with a glitchy boss dd7 changes the amount of the in this case mix getting through. The important thing for me is to be able to use the pedal to go completly dry and then swell in the wet signal.

I can probably just try the parallel idea with alligator clips but I wonder if you have any further insight on this set up. Thanks!

Is this for a already incorporate wet/dry control on a digital circuit?
As in, what are we controlling? Analog audio or 5V/3.3V DC?