The question is mostly for SS (@BeatBuddy_Support), but others can contribute by telling which models you got working with MM and what are the (three) specs of the exp pedal? See more below.
My knowledge of expression pedals is mostly from this page + I studied a year of electronics in university.
I’m interested in the three aspects:
What wiring is the MM expecting?
Based on other discussions on this forum a TRS plug is to be used. But is the wiper in ring or tip? And how does clockwise and counter clockwise connect to the tip (or ring) and sleeve? If calibration can reverse the order of min/max (toe/heel) then CW and CCW don’t matter, only the wiper matters.
Does it matter which internal resistance the exp pedal has?
I’m sure the calibration gives some pedal options, at least for pedals in the same ballpark. But is it from 5k Ohm to 50K Ohm? What are the limits of resistance that MM supports?
Linear or logarithmic taper?
I’m hoping a linear works with MM, but does it?
The reason why I want to go deep is that I’m trying to see if I can use the same exp pedal with HX Stomp, with minimal re-wiring (or no wiring at all). Stomp uses a TS pedal, but TRS is easy to rewire to TS. Note: I don’t have any exp pedal currently.
FWIW… I took apart my Roland EV-5 Expression pedal to trace out the wiring (not a clue if this works with the Maestro. Suspect it would). I measured the potentiometer values as there were no markings on them. For how it works I don’t think the value of the main potentiometer is too critical as all it does is function as a voltage divider to the voltage applied across the ends of the pot. I don’t know if the pots are linear or log, but would suspect linear.
I’m thinking about building a desktop expression controller with a standard rotary pot in a project box which could be handy at times with a Hotone Ampero Control. If you have some soldering skills it would be cheap and easy to experiment with some potentiometers wired out to a TRS cable.
Both the Maestro and the Aeros have expression pedal inputs. You would almost think Singular might consider manufacturing their own and selling it as an accessory. That way you could be sure it worked with their product line. Or work a deal with another manufacturer and rebrand an exp pedal with the Singular Sound logo.
Is it possible for you to test it with Maestro? Others have guessed that the MM would require wiper to be in the ring, but with EV-5 it’s in the tip. If it would work then that would be good knowledge
P.S. I found the official info for EV-5 and it matches exactly to yours
Edit: Except the colors white and red are swapped, but it shouldn’t matter
Nope, can’t test it with a Maestro. Don’t have one and no plans to get one.
Interesting on the wire colors. Going to pop the back off the EV-5 again and recheck.
Update… Checked and confirmed the wire colors. Roland’s service notes are incorrect . The red wire is indeed connected to the wiper and the white to an end of the pot .
I’ll try to at least gather the pieces of evidence that I have:
I think the Quik Lok Universal had two modes, one where the wiper is in ring and one using tip. Also I believe the resistances are vastly different in these two modes
50 kOhm with both tip and ring modes.
I think it has wiper in ring.
So it might be the case indeed
But, this also has the wiper in ring. So it seems that’s not the case It also has 50 kOhm resistance
Conclusions
So, around 50 kOhm might be a requirement for MM. Wiper in ring works, perhaps also in tip, but can’t be sure. Taper information is nonetheless more difficult to find so hard to say, but if I’d have to guess I’d say linear
Can anyone from SS confirm any of these? (@BeatBuddy_Support? @moderators?) How flexible is the MM with these features?
The point being that we shouldn’t have to try to work any of this out for ourselves!!! Come on Singular Sound. Is it that hard to spec your interfaces?
Just to inform you, I finally got reply for my support request via e-mail:
Hi Aapo,
Thanks for reaching out. We’re currently looking into your questions and conducting some internal testing. We’ll do our best to provide you with the information you need as soon as possible.
Keep Rockin’!
Daniel | Customer Support
When I get the final reply I’ll report the results here
. The red wire is indeed connected to the wiper and the white to an end of the pot 
.