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Expression pedal modding question

Messages
767
I got a custom made Dual ME ("Mini Expression" pedal with two knobs and a footswitch toggling between the two of them ... see pics below) from T1M some years ago. Worked perfectly with my EP-2 phaser, also with my Strymon Timeline.

Now I recently got a DvK Goldtop, a dual fuzz + vibe pedal with expression control jack for vibe speed. I'm currently rearranging my pedal board and I would like to control the DvK speed with the Dual ME.

Problem: The Dual ME won't go down to the slowest possible speed. Setting either of the knobs fully CCW will give me about the speed of the DvK speed knob set to 10:00. Turning the Dual ME fully CW however will give the same maximum speed as the DvK speed knob maxed.

Now I would like to mod the Dual ME to reach the slowest possible speed on the DvK. Of course exchanging a pot might do the trick, but I would prefer a simpler solution, like adding a fixed resistor to the left pot. This way the left knob probably wouldn't go up to full speed anymore, but that's okay ... I would use the left knob for the slower speed range and the right one for the higher speed range then.

Questions:
1. Would this work?
2. What resistor should I use?
3. How and where should I connect it? TRS expression pedals are a mystery to me anyway, why are there three poles when two would be enough? ;-)



 

wrightdude

Member
Messages
4,274
You might want to confirm with DVK but sounds like they are wiring the pot as a rheostat rather than a votage divider and expecting the exp pedal to "replace" the pot in the box?


You can probably add a resistor to the end of the pot in the exp pedal at the end opposite of where the wiper is when you want the extra load... to equal the value of the pot in the box. I.E:

[added resistor] = [pot in box] minus [pot in exp pedal]


Probably a worthy experiment... but wouldnt hurt to check with DVK to verify their exp implimentation?
 
Messages
767
You might want to confirm with DVK but sounds like they are wiring the pot as a rheostat rather than a votage divider and expecting the exp pedal to "replace" the pot in the box?


You can probably add a resistor to the end of the pot in the exp pedal at the end opposite of where the wiper is when you want the extra load... to equal the value of the pot in the box. I.E:

[added resistor] = [pot in box] minus [pot in exp pedal]


Probably a worthy experiment... but wouldnt hurt to check with DVK to verify their exp implimentation?
Thanks ... before buying the Goldtop, I sent another technical question (whether or not the Goldtop uses an LDR circuit) to DvK through their website contact form. It's like 3 weeks ago and I didn't get an answer to that question yet ... that's why I decided to try here first with my new question :)

I have no big knowlegde of electronics and can't tell a rheostat from a voltage divider :)
But yes, putting a cable into the DvK Goldtop expression jack "replaces" the on-board speed knob. Putting in a mono patch cable sets speed to max. Connecting the T1M Dual ME w/ a TRS patch cable deactivates the on-board speed knob and "hands over" speed control to the Dual ME.
 
Messages
767
Actually, I am not sure what value is in the exp pedal? Do you have an ohm meter?
Yep, I do. Just measured:
Tip to Ring: 10,8 kOhm CCW / 0 kOhm CW
Tip to Sleeve: 10,8 kOhm CW / 0 kOhm CCW

So it should be a 10k pot, like in a Roland EV-5, right?

Can you open up the DVK and see what value the pot is?
Just opened it up. There's two layers of PCBs in there, impossible to see the pots. I don't want to take everything apart, I fear that I might destroy something or wouldn't be able to re-assemble correctly.
 






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