Diode ladder VCF

Filter based on the EMS diode ladder filter.

Well, here is another classical and very special filter based on the EMS diode ladder filter!
This filter has a sound of its own and is the signature of the classical Pink Floyd's song "On the run".

My aim here was to design a quite faithful copy of this mythic filter while using components that minimize the burden of selecting a great number of matched transistors. This is why I used transistor arrays (CA3046, CA3096). However, because the CA3096 has become a rare part and is now overpriced, I have also designed a PCB with discrete trannies to replace it. As for all the other filters of my YUSYNTH project, I have added an input and an output buffer to adapt this filter to the input and output levels of my modular system.
I also added an input for voltage control of the resonance : everything was there in the original module but was not made available, probably because of the limited size of the patch pin matrix of the AKS/VCS3...
Because, my power supply standard is +15/-15V, I have included a power regulator IC (78L12) to convert +15V to +12V and a single transitor voltage regulator -15V to -9V (I wanted to use a 79L09 but changed my mind when I realized that this voltage regulator is quite a rare part and is difficult to source).