0v vs. Gnd in Elektor formant.

[talkboxert]

I'm bringing back to life an old Formant, powering it from a doepfer 12v PSU. The tracking on the VCO's is ok, and one of the VCF's works as well.

As this is a semi modular design, I want to hook up the internal signal path next. This flows from the vcf where all VCO's are internally conected to the VCA and is output on a "COM" module, that has EQ and output sockets.

What i run into is the com pcb, opossed to all other modules has no clear ground connection. In stead it has a connection named 0v.... All the othe modules have the symbol, something like: https://www.mica.co.za/wp-content/uploads/2019/09/TEXT-INSERT-IF-NEEDED-EARTH-GROUND-SYMBOL.jpg

I'm not very good at electronics so apologies if this makes no sense.
But it looks to me like the 0v is derrived from the +/-15v (or in my case 12v) lines by c11,c12.
Do I also connect ground here or leave the 0v unconnected to the rest of the case. I've posted a pic of the schematic that does show a ground symbol on the far left...... The other modules are connected to the ground connection on DC end the doepfer supply (DIY 1 supply). The case is made of wood.

Links, I cant get the image to show up here somehow
https://im.ge/i/QOGzOD
https://im.ge/i/QOGnUp

[blue hell]

0 is ground there - in the last link you gave.