Apologies in advance for my lack of technical knowledge.
Situation in a nut-shell.
I want a eurorack trigger signal to start / stop the patterns on a KR-Mini drum buddy.
The drum buddy is clearly not expecting a eurorack trigger signal at its foot-switch input.
What engineering magic (DIY, module, external box, ???) do you believe would be needed to achieve this feat?
I have looked into it some. A friend of mine suggested the traditional foot-switch “shorts out the tip to the sleeve” and causes the drum machine to start / stop.
Not sure if that’s useful.
Hopefully this post / new topic does not run up against the forum rules. If so, mods, please feel free to delete. In my defense, I performed a search before posting and did not find an identical topic.
Thanks in advance for any advice.
hey, good question!
You could describe it as a short but I think that’s confusing. think of it that a footswitch connects the tip and ring of the cable.
in eurorack, the ring is always ground, and no signal is ever passed through it. so you’ll need to do something weird or custom and possibly dangerous for your gear. but it’s totally doable.
you basically need to connect the tip and ring to the in/out on a momentary VC switch, and then send a gate to the CV in
Thanks for your reply and suggestion.
I’m a bit out of my depth still…
Are you saying, in the below diagram, I would connect a eurorack gate to 1 and a lead from 2 to the drum buddy foot-switch “in?”
Seems more like you’d need to interrupt the signal that travels through the cable of a footswitch, perhaps with a breakout cable and some vca’s. Not official advice
If I’m understanding correctly, you’ll want to attach your gate to 1, and your leads to 3 and 4 (or 2 and 4)
sorry, you need a dedicated circuit that will take your +5v or +10v and use it to control an analog switch. (IMO.)
there are CMOS parts specifically for this, such as the venerable 4066:
and you may also be able to get away with a MOSFET, but will require some more design work, e.g.:
i think that is probably safer for your drum machine than hooking up eurorack outputs directly to the FS inputs. (which may or may not be designed to handle whatever output impedance your module happens to have, which can vary a lot, down to a scorching 0Ω.)
as poster below points out, you can also use an electromechanical relay which is conceptually similar. seems like overkill to me for the application when solid-state solutions are smaller, cheaper (by 10x) and can operate at much higher rates if you so desire. (i would use a relay when there are e.g. vast differences in power between the two electrical systems, or actual safety issues - such as controlling lighting or 120V AC power circuits.)
finally a reminder that your first step really should be to measure the voltage produced / expected by the footswitch circuit, so that a truly informed decision can be made.
but if you don’t want to make such decisions then buying a relay module is certainly safe (if expensive.)
this sounds like the difference between a V-Trig and an S-Trig (the Korg MS-20 uses S-Trigs)
I wasn’t able to find any kind of technical info about the KR-mini - but I’m sure there must be info out there.
This might be what you’re looking for:
I found it looking for CV control over the sustain jack of an external synth. Dronetown or bust.
It’s a CV controlled relay built into a Eurorack module. The relay will short dry contacts, as in a sustain pedal. Also has a two input comparator built in with a threshold knob, which will compare your control signal to another dynamic one or a simple static offset.
Can be used for a lot of other stuff, like controlling LED strips or anything that runs off a different voltage level/source.
And it goes ‘ka-chunk’, which is cool. (There’s a real, physically actuating electromagnetic relay inside.)