Mix It, Baby!

Multiples I have no use for in my small modular system any longer.

Multiples I have no use for in my small modular system any longer.

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.

So, out with the Multiple! The lower bus board on my Doepfer PB case is hard to reach, so you always have to take out more modules than you wish

So, out with the Multiple! The lower bus board on my Doepfer PB case is hard to reach, so you always have to take out more modules than you wish

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:

A Doepfer A-138u dual micro mixer took the place of the Multiples.

A Doepfer A-138u dual micro mixer took the place of the Multiples.

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.

Here it is fully used. I'm mixing the VCO signals before the filter in the lower section and the filtered audio, audio from the laptop and audio from the sampler in the upper section. The green wire takes it to the headphone amplifier

Here it is fully used. I’m mixing the VCO signals before the filter in the lower section and the filtered audio, audio from the laptop and audio from the sampler in the upper section. The green wire takes it to the headphone amplifier

And here’s the whole shebang:

Hearing das music, watchen das blinkenlichten!

Hearing das music, watchen das blinkenlichten!

Modular synthesizers are very immersive, can’t you tell?

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