Hi Paul,
Sorry about the slow reply, the notifications were not set up correctly so I missed your post.
Just wondering if the Gecholoop's 3.5mm MIDI jack is wired to the "A" or "B" standard. I'm assuming it's Type-A, but don't want to damage anything...
Yes you're right it is "A" standard, like used by Korg, IKMultimedia, Make Noise and others (I followed
the specification here and decided for that group of devices, so for example the Uno synth can be connected directly with a 2.5mm to 3.5mm Jack cable).
Of course better safe than sorry but the risk of damage should be very low, Gecho definitely won't get damaged even if the other device short-circuited its output. The other way around, if the incoming signal was reversed, it will just do nothing, next to the octocoupler there is a protective diode and a current-limiting resistor. Quite often I mistakenly connected one device's output to another, forgetting changing the I/O selector switch, but nothing happened - the voltages and currents involved are very low.
Also, any update on the CV input capability? I've just got my hands on a Teenage Engineering OP-Z, and hope to start exploring the pair.
It is on the TODO list, I definitely don't want to leave this bit unfinished therefore it's still printed on the front panel, next to that switch. But for the next update I want to finish everything around the MIDI first, and that is almost done. I don't have the OP-Z, but if it has a MIDI output then there is plenty of things you could already do with this combination.
Happy to hear you enjoy the loopsynth, if you record something to share with us, please do not hesitate to do so!

Cheers,
Mario