No reason! Thank you for spotting that!
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Speaking of VCAs, any idea why I have these little spikes in the (simulated) VCA output? Green is input, red is out. I do not have them if I put the signal through a filter.
I too want to start putting diodes on my power supplies, and I had a look at how befaco do theirs:
There’s a BOM file where it says D1,D2 are 1N5817 - which are Schottky diodes with low Vf, the datasheet quotes they are intended for polarity protection among other things.
I have’t built or tried mine yet, but I figured if it doesn’t work I can just short them out on the board and just continue to live life on the edge with unprotected supplies.
Cheers
I’m just guessing, but there is probably some input capacitance inside the model of your VCA. If you drive those caps with instantaneous edges, like in your square wave, perhaps the simulation will have them overshoot. Try with a square wave that has some non-zero rise time, even a couple of ns might make a difference.
Cheers
That’s the “series diodes” option here:
(I prefer diodes to ground myself, but that assumes that you only use power supplies that can deal with a short.)
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I use series 1N5817 like that all the time. No problems. Then again I use shrouded headers and I don’t think I’ve ever connected power backwards on an assembled module. (On an IC on a breadboard, not so much.)
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Interesting, i will try it, thanks! 
Something else: is it enough to use a single pin for +12V -12V and 0V/GND each for the interconnection?
I tend to put GND on all the connectors I can. Nothing empirical behind it, but I figure you want your ground plane connected in as many places as possible:
I don’t need -12V on my latest front panel, but here’s what I did. Front Panel:
Which connects to the Back Panel (Brains!):
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I am making progress! Noise circuit works, oscillator works! Still missing parts for the mixer and the filter. I made a stupid mistake in kicad and swapped +12V and -12V for one of the TL074 (postet in the litany thread already), but let’s see if I can fix it! 
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Looks great! I want it!
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I will of course make the files available, but I would rather wait till I have tested it I already found that I mixed up the power on one Tl074 and the pots for mixing, decay and probably the attenuverters are the wrong way 
I am still waiting for parts to test the filter and vca and all together.
Who has two thumbs and does this on a regular basis?
(Of course I checked them before having the PCBs made. And they were right. For certain values of right. Namely wrong.)
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Aargh dammit! You had me thinking - I checked and sure enough the pots on the Superspreader are the wrong way.
That is wrong isn’t it?
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I’d say… it depends
It’s called CV ATT(enuation), so the more you turn it to the right, the more it attenuates…
Seems right to me, even if I find it more natural the wrong way
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I have fixed a few issues now, but more remain. One is that I have a bleed of the envelope in the output. So, I always have a click sound even when I turn down vco and noise completely 
It’s around 1V , the envelope max is around 10V I think. Anyone got an idea what can cause this bleed?
Sounds like what happens with the k25 EG, although a bit worse. Which envelope circuit are you using now?
I am using this one, which is from Barton
bmc018:
Edit:
Not Barton, it’s Barton + electricdruid (Design a Eurorack “Vintage VCA” with the LM13700 – Electric Druid)
I will look for the k25 EG thread. Could you solve it there?
Sorry I noticed that I did not describe that well! The envelope itself seems okay, it goes back to zero as expected. the problem is that it somehow gets into the (audio) output. So I suspect the VCA (that’s why I posted the circuit of that and not of the envelope).
Even when there is no (audio) input at the VCA, as soon as the envelope comes in (at the VCA CV), it comes out of the output (scaled down to 1V max, but still). It is as if there was a 1V constant signal at the VCA input, but I measure 0V there…