Active vs. Passive Multiples In Modular Synthesis

Chris Meyer (Learning Modular) shared this video look at active vs. passive multiple in modular synthesis. 

Video Summary:

There is a lot of debate and confusion among modular synth users about whether or not you need an active, buffered multiple to control multiple VCOs accurately in a modular system.

The answer is “it depends” – on the buffering and output impedance of the module sending the control voltage, and the input impedance of the modules being controlled. Some combinations work fine with a passive multiple. Some most certainly do not, going out of tune within +/- 1 octave.

This video – excerpted from a longer one in my “Learning Modular Synthesis: Moog Mother-32” course – demonstrates a case where passive multiples do not work. As a result, just to be safe, I keep a few good buffered multiples – like the Intellijel BM or Malekko Performance Mult – in my system, just to be safe. (I also have the Xaoc Dvices Warna II and AJH Synth V-Scale arriving soon.)

4 thoughts on “Active vs. Passive Multiples In Modular Synthesis

  1. This would not be an issue at all if manufacturers would stop tacking 100-1K resistors on pitch-critical CV outputs in the name of “protection”. Opamps are more than capable of driving many pitch CV inputs at once with no attenuation and scaling error. And nearly every commonly used opamp has built-in short circuit protection already. It’s a practice that’s been carried over from the 70s (when the opamps of the day actually *were* more sensitive to short circuits), yet tons of modern modules leave it in anyway. And this has nothing to do with The Sound/Vintage Authenticity or anything like that. There are even easy ways to incorporate the protection resistor without raising the effective output impedance, but not everybody does this.

    Funny thing is most of these active mults will also add the ~1k resistor on each output, which actually defeats the entire purpose of buffering in the first place because *those* CV outputs now cannot be passively multed. They are repeating the same mistake that they are supposed to correct!

    It’s a problem rooted in sloppy design, and the consumer ultimately gets screwed because instead of buying a $35 passive mult they have to buy a $80 or more active mult. And it’s one more thing to worry about while patching.

  2. I find I can split pitch CVs from the CV.OCD with just a Stackable and it doesn’t mess up pitch tracking over 7 octaves or so. Can’t do that with the MicroBrute’s pitch CV output.

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