It's the size of the modules, and their power supply requirements. See
here for more information.
Nice looking synth. What size jacks are you using, 6 mm?
One of the problems with eurorack modules is that the controls are often very closely spaced.
Hi Steve yes 6 (.3) mm jacks.
The modules i'm making started out at 13cm by 25cm.... their size is difined a bit by what scrap wood I find and how much i can be bothered cutting this to size, my next modules will all be 13cm by 21 cm as I found a chest of draws i'm currently cutting up.
I like the idea of 3.5mm jacks, nice to have less bulky wires around. Problem i'd find is because i use found wood i'd probably struggle with the length of jack socket and thickness of wood. I've minly been gettin g around this by threading the panels with a tap and die set.
I'm very early on in build and am deffo a newbee, i'm already thinking this synth will end up huge, but then i've oggled those 60's floor to ceiling synths for a long long time.
Sacking off the above VCA circuit after discussions here and your links. Will build the standard VCA's from MFOS instead on stripboard, fairly straight forward circuit, most of the parts I have to hand anyhow.
Some of your module names are hilarious!!!!!!!!!