I just ran into a problem were I used a Tiptop Audio Buchla 281t (the Quad Function Generator) to control an Intellijel Quad VCA and the 281t locked up and produced a constant hum. As it turned out I had to use a buffered multiple in between, which is related to the impedance not matching.

It would be awesome to add some information about module parameters, like the impedance, voltage range, trigger width and so on, this would make it much easier to figure out which modules are compatible and which might need some tools like the aforementioned multiple or an offset/attenuator to make them work together smoothly.