I salvadged 32 units of THAT2159 VCA chips from an old Behringer digital mixer. Been planning to build Eurorack VCA's from them and successfully breadboarded a very simple design based on the datasheet and the GMSN Pure VCA (that uses 2181 if I recall correctly).

Breadboarded and works fine!

So I this is a very simple VCA schematic with only two knobs for cv attenuation and bias. It's always exponential (that's the VCA chip). I'm not particularly fond of 2hp designs so it really doesn't make much sense to do a single unit one. I'm aiming for a dual now, but also toying with quad, dunno.

So this time I'm really going with ui first approach which will decide the pcb layout. I feel I have two options:

A 4HP version would make me have to do a panel pcb and a back pcb, I really can't imagine I'll fit 2 soic8 and 2 sip-8 as well as euro header there. Maybe the 6HP version here would allow me to do just one PCB?