Seems to work (found one stupid mistake already, had to swap two pins on the opamp on the ctrl board)! But I think something is still wrong with the envelope, it stays constant a little too long at the beginning, I think. I will measure and show a few pictures (and sound)…
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Oh, that was just from the triggering with the button, it made the envelope too long, because I can not push the button for just a millisecond, so the sound did not really kick 
via trigger in it just sounds awesome!
It’s a really nice kick with lots of options and sounds (especially v/oct!!) but if you really only need a great sounding kick with no frills, I would recommend the one by @Krakenpine , Way less complicated! 
Huh. I’m very surprised there isn’t a pulse shortener on the input. Like the Barton Analog Drum for instance:
I’d say it’s needed especially with a push button trigger.
Yes, for the button I agree, but you can use the module as a bass voice and for that it is nice to be able to have a kind of gate in for longer notes!
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Did you get everything working on this thing? I am preparing an order for jlc…
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Mostly yes, and I also asked Befaco if I might share it and they are happy with it So, I will upload the project on GitHub very soon. I had to fix one opamp where I mixed up the inputs and one resistor value for the button was wrong, but I think that was all. Buuut: Accent is not yet working! It might be because I have not installed the capacitor (C16, 4.7uF, I currently don’t have that value), but I suspect it’s something else. So maybe you all might want to have a look?
The behavior I have is that the output volume is always the same, independent of what I put in the accent jack or where I put the jumper… I have not yet measured anything, did not have the time
original:
edit:
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If I am understanding this correctly, which I may not be as I have not designed any circuits using the LM13700, the accent is used to control the gain of a second VCA. In the original circuit, the buffer opamp is fed 9v and the input accent cv is added to this to increase the gain. In your circuit, you have a comparator giving negative voltage, then flipped with an inverting opamp with gain of 1. That will give the same voltage no matter what you supply to the accent. The voltage out of either of these circuits is converted into a current with the transistor and fed into the LM13700 VCA.
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I suspect what you intended to do and left out was a 100k resistor from U3C pin 8 to pin 9. That would turn it from a comparator into a unity gain inverting summer.
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Exactly! That’s what I wanted! At least it should be an easy fix
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In theory, yes, an easy fix! But where do I place that additional resistor? 
At least on the boards that I have it will be easy…
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I made some space and placed the missing resistor! I also fixed the opamp on the ctrl board and I made the slot for the slide pot on the panel slightly wider (0.2mm) because with my slide pot it was a bit tight and I had to sand the edges slightly. So, I think it’s perfect now, @BenRufenacht
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In the first pcb version I ordered there are two things to fix. I post this here for the people I sent some boards to. I am sorry for the inconvenience
The version on GitHub has these fixed!
First: on the opamp on the ctrl board one input is reversed, so you need to bend legs 5 and 6. 5 needs to be inserted into the hole of pin 6 (I know it’s ugly! And 6 needs to be connected via wire to the right leg of R29.
Second: for the accent to work properly you need to add a 100k resistor between the right leg of R75 and the left leg of R77.
I also added another 10k parallel to R73 to lower the „default“ accent level to make the accents more noticeable, but that is down to Taste I would say.
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That C102 4.7uF capacitor to ground right on the output of IC100A seems very strange to me, all it does is seriously load the opamp’a output.
Should a resistor be in front of the capacitor? Maybe R26?
Edit: C16, U3A and R63, respectively in your “untested” schematic.
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Does anyone see any issue with replacing the 100k slider with a 50k? It seems to just be a voltage divider, so I should get the same result, right?
Should be no problem, but you need to adjust R25 as well to get the „correct“ nonlinear response. If you use 50k instead of 100k then I guess you want 1/2 of R25 as well. But don’t take my word for it
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Maybe first I should ask where you got your pot with the green led? I want to switch to 50k because that is all I can find in stock of the green led version of the slider. That or settle for red or orange led. But, that green led would really tie the room together.
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I wanted red leds and could not find them xD
I got those sliders from RS-components, I can check the link later, but you will find them if you search for ptl60 or similar. I made the footprint such that also the standard sliders without led from tayda would fit, but then you don’t have any led. Should have made a spot for a separate one maybe on the pcb…
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Looks like RS doesn’t have any 100k in stock, at least on their US site. Mouser and Digikey both have the reds and oranges. I may go with no led to simplify things.
If it’s 100k (I don’t see the value on either the Befaco schematics or Sebastian’s) then it’s complicated — there’s not only a 15k to +12 V but a 120k to virtual ground and 220k to -12 V, all of which will modify the slider response. And you can’t modify the 120k without also modifying the 100k on the jack and the 27k feedback. However the effects of the 120k and 100k are small and probably you could leave them alone.
Green is 100k slider + 15k resistor, blue is 50k + 7.5k.
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I think I can live with that change.