Multiples seem like such a good idea when you’re building a small modular synthesizer that has, well, multiple sound sources. They’re not. Here’s why:
They take no current from the bus board, don’t even have a cable. So, they’re not active. What you plug into them is essentially switched in parallel. Control voltages are NOT added, but interact in mysterious ways. Gate signals suffer a fate depending on when they arrive. Again, unpredictable. For gates, you need an “OR” gate (“If you get my meaning, Mr. Frodo.”).
Total chaos reigns if you try to join audio signals with a Multiples module. The sum audio signal gets very low-volume but when some sources have a pause, the sum volume suddenly jumps up. And sometimes not.
What you need is a mixer. I already have one in my system, a Doepfer A-132-4 Quad Exponential VCA Mixer. It is fine for mixing VCO signals before sending the sum through a filter. It takes two individual control voltages per VCO signal, one for loudness / aftertouch and one envelope CV for shaping the note. But it is no use for mixing different finished, filtered audio signals. This is:
The upper output is normalized to the top socket of the lower three inputs, meaning: if you don’t use that socket, you’ve got yourself a mixer with five inputs. The top three inputs have attenuating potentiometers on them but they’re on the backside, on the circuit board. Apparently, Doepfer doesn’t do micro potentiometers. Anyway, I’ve yet to use those hidden settings, mixing audio signals or control voltages works fine without them.
And here’s the whole shebang:
Modular synthesizers are very immersive, can’t you tell?