Where it’s att

The idea originally was to go slow, adding a module at a time to my synth setup with months in between. Ha.

Here’s the thing. Suppose you have a perfect synthesizer. What do I mean by perfect? Perfect for you, for one thing. Not perfect for anyone else. But for you it has the features you want and has no features you don’t want. There’s a perfect balance of oscillators and filters and everything else. I also mean perfect for its size. Given, say, a particular number of oscillators, it has the right mix of everything else.

But you want another oscillator, so you add one. Now it’s not perfect any more. The balance is broken.

The new oscillator is one more thing you’d probably like to control with the keyboard control voltage. That is, you now have more destinations you’d like the keyboard CV to go, and that means whatever number of buffered multiples you may have had before, now you should ideally have more.

If, like the Befaco Even VCO, your new oscillator has CV inputs that do not have knobs to adjust the degree to which it responds to those inputs, then you need to attenuate those CVs before sending them to the oscillator. So whatever number of attenuators you may have had before, now you should ideally have more.

Your oscillator has outputs, and what are you going to do with them? Send them to a filter, probably, along with other audio signals. Which means whatever number of mixers you may have had before, now you should ideally have more.

The Mother-32, which is probably not perfect for me but let’s say it’s close, has one buffered multiple, with two outputs. It has one attenuator, if you count putting a signal into the Mix 2 input of the VC mixer and “mixing” it with 0 V from Mix 1’s normal connection. It has two mixers, each with two inputs and one output, which can be combined to mix three signals to one output… unless you’re using one of the mixers as an attenuator, of course. That’s not a huge amount of capacity for multiplying, attenuating, and mixing. And now I’ve added a VCO.

(And the above discussion does not even take into account that, as mentioned, the Befaco VCO can’t use the Mother-32’s keyboard control voltage directly, and the recommended fix is a buffered multiple. But not the M32’s buffered multiple. Whatever impedance mismatch, or whatever, is responsible for the V/Oct tracking problem on the keyboard CV output, the same evidently exists on the buffered multiple output, so you get the same mistracking with the keyboard CV run through the buffer before going to the Even VCO.)

I’ve also added an ADSR, and, as also mentioned, its usefulness is somewhat limited by the inability to use it with the Mother-32’s VCA. And that means now I should ideally have more VCAs. But I can wait on that. The VCO’s needs and especially its need for a better keyboard control voltage spur me to more immediate action. Taking advantage of a 15% off sale going on, I ordered:

  • Mixer from AI Synthesis. A simple active three channel mixer. Low cost, looks like it’ll do the job, and it has good clear build guide and a build video. Also, it matches the ADSR, and the red knob on the Even VCO.
  • MiniAtt from Żłob Modular. Can also serve as a passive two channel mixer. Inexpensive, compact, pretty clear build guide. Red panel. I thought about the AttenuMix, which apparently is discontinued but still in stock, and which seems to be about the same thing but three channels and wider. And blue. Decided two channels are enough for now.
  • Buffered multiple from horstronic. Looks good, though I had to dig to find a schematic and if there’s a build guide online I can’t find it. Should be straightforward though. There’s a cheaper buffered mult from Barton but even though it has four channels to the horstronic.’s two, I like the looks of the latter one better. For one thing, it has buffered outputs as well as inputs. The Barton just has buffered inputs. Also, the Barton is designed so it should be unity gain. The horstronic. has trim pots to calibrate the gain. I guess all my years doing physics experiments have left me feeling that designing something so it should behave correctly, on paper, isn’t as good as designing it so you have control over its behavior and can make it behave correctly. Neither one has any visible red whatsoever, though.

I built the MiniAtt tonight. BOM: 5 jacks, 2 pots, 2 switches, 2 resistors, circuit board, panel, mounting screws. Took me all of about 25 minutes. It works.

MiniAtt from Żłob Modular

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