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Macbeth Micromac-D MIDI controlled VCF cutoff
Old 20th October 2013
Macbeth Micromac-D MIDI controlled VCF cutoff

I wired up my Micromac to allow MIDI control of the VCF cutoff frequency through the MSRK MIDI-CV interface. The MSRK has 4 unused auxiliary CV outputs. As outlined in the Kenton MSRK information sheet, I located the summing point of the filter cutoff and connected the MSRK CV Aux 1 to that, using a wire with a 100k resistor attached. I soldered the resistor in between the wire and a piece of shrink tubing. I was informed later that the preferred method is to solder one lead of the resistor to the summing point and the other to the wire and then connect the wire to the MSRK. Once connected, I programmed the MSRK to enable Aux 1 control via key velocity and set my minimum/maximum values. Here are a couple picture I took of where to connect the wire to.

The solder point is towards the upper part of the synth board, just below LFO2.
Macbeth Micromac-D MIDI controlled VCF cutoff-micromac1.jpg

Close up view
Macbeth Micromac-D MIDI controlled VCF cutoff-micromac2.jpg

Connection to the MSRK
Macbeth Micromac-D MIDI controlled VCF cutoff-micromac3.jpg

Sysex to configure Aux 1:
F0 00 20 13 10 00 20 00 10 01 7B F7 - Aux 1 controller off
F0 00 20 13 10 00 20 00 10 01 7D F7 - Aux 1 controller pitchbend
F0 00 20 13 10 00 20 00 10 01 7E F7 - Aux 1 controller velocity
F0 00 20 13 10 00 20 00 10 01 7F F7 - Aux 1 controller aftertouch
F0 00 20 13 10 00 20 00 11 00 xx F7 - Aux 1 controller min value where xx = 00h-7Fh (0-127)
F0 00 20 13 10 00 20 00 12 00 xx F7 - Aux 1 controller max value where xx = 00h-7Fh (0-127)

You can also use the Learn Function to set a knob/slider to control Aux 1 by pressing the learn button, move the desired knob, press note C3 on the keyboard and then note C5 to save. When I tried this with my controller, it froze up the Micromac, but upon powering it off and on, it was fine and I could use the slider to control the filter. Not sure what happened.

As you can see, the modification is quite easy. If I can get the schematic information, I would like to wire up the three other aux CV outputs to VCO1/2 pulse width and the VCA.
Old 28th September 2014
I looked at the Kenton info that Macbeth provides. On page 4, where it says cutoff to CC 16.......that's simply for controlling cutoff via MIDI controller, correct? What you've done here would allow for filter automation via MIDI CC, for instance within a DAW, right?
Old 29th September 2014
Yep. Just wire up Aux1 with a 100k resistor to the solder point in the image and you will be able to control the filter cutoff from any MIDI controller.
Old 11th October 2014
I'd love to gather opinions about the best circuit points to patch into. Filter cutoff seems like a great place to start. I wonder if there are some less orthodox CC modulation inputs that people have tried, that would be worth a go. There are several aux cv outputs on that Kenton and I'd love to make use of all of them in the most interesting ways possible! Who's got ideas?
Old 31st October 2014
Also, is it possible to patch two Aux outputs from the Kenton into the same point, using these directions? I'd like to rout velocity to the filter, while also having an additional CC for it, as well. Does anybody know for sure if the 100k resistors are adequate for summing CV from two outputs on the Kenton, along with the other CVs that sum at that point? Is there danger of damaging the Kenton, for instance?
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