Mux/demux CV's?

#1

I have never used but understand control voltage, but so far have only been controlling my axoloti via midi. I am interested in knowing if it is popular to mux/demux CV's. As an example, I have a controller with many analog pots, toggles, and momentary, and would like to have a convenient 'plug in'... with say half a dozen wires that get demuxed and fed to axoloti inputs, instead of a heap of wires. I have some ICs that can do this, both analog/digital, and wonder if it is common (or even do-able)? Just looking for feedback from those more in the know... thx.

#2

Are the CV's you plan on Mux-ing all static CV's? If some are LFOs or moving, you may need to have Track and hold or sample and hold circuits to keep from weird glitches etc.

I went for the more expensive route myself and got a CV to MIDI CC converter and convert the CV's into MIDI continuous controller commands to go to the Axo. I can justify the cost because I control more than the Axo with it. I bought the Doepfer A-192 which turns 16 CV's into MIDI CC commands. There are others out there too of course and also some OEM solutions. Do a Google on Custom MIDI controllers and you will get a bunch of hits. "DJ Battle Controllers" were a big thing once.

#3

thank you for that information... @Ersatzplanet
truth is, all I have done with the axo to date is via midi CC... but read about benefits of CV/'real analog' etc, so thought there might be an end benefit in having a true CV version of my controller

#4

The cool thing with the Axo is that you can of course have both MIDI and CV control if you build it right. The Analog inputs (and of course the CV ins you would have connected to them) are running through A/D conversion at a higher bit depth than the MIDI ins so may be smoother, but you can also add shooting modules to your patches too. I myself am just too lazy to make the PCBs and circuitry to use CVs and have planned all along to tase the Doepfer A-192 in my rig. They are no longer in production but Analogue Haven has some left over. That are limited too of course (only CV in the 0 to +5V range) but useful for what I want to do with it. Those 16 inputs and the full complement of possible knobs/switches directly connected to the Axo are quite a lot of control places. I have a bunch of Vactrols laying around and That is yet another option that needs very little extra circuitry. Some surplus plates like Electronics Goldmine have them in sale often. That is the coolest thing about the Axo - lots of options.

#5

not familiar with 'shooting modules' James but sounds interesting. My controller is currently midi so maybe I could just tap into a bunch of the analog ins for some new pots and whatnot atop the axo enclosure I'm using...The axo pictured here is my concept 'clip on'

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#6

LOL! Autocorrect at work again. Substitute "Smoothing Modules" as in Lag Processors and filters, for "Shooting Modules". The combination of a CV to MIDI CC module and the connections already built into the Axo for pots and such could give you more than 30 controls available. More than the Axo could process probably. The main hurdle with external CV is that it almost always much larger than the 3v range that the Axo wants to see without damage. If you don't ride giving up some accuracy Vactrols are a good solution. Also simple transistor circuits. Seeing your controller, the first thing I thought of was Force Sensing Resistors. We (Synthwerks) make a whole line of modules based on them. I could easily see them on that controller of yours doing modulation duties and more.

#7

There is a force sensing ribbon underneath the position ribbon and it sends velocity based on pressure. Position ribbon sends notes. The 4 brass pads are capacitive touch and also send notes. I may eventually replace them with FSR's.

#8

Typically you can get FSRs in three commercial shapes, small and large circles, large square, and long strips (used under keypads to generate aftertouch). Sparkfun has a bunch of different ones too, many that emulate pots and are position oriented too. The market has expanded a bunch for these.