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Thread: Transforming an old Numark mixer to a midi controller

  1. #1
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    Transforming an old Numark mixer to a midi controller

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    Hi there I'm hoping to find someone to guide me because It's not my domain and I'm totally lost. i'm assuming I'll need a custom pcb but how do I design it ?
    Thanks
    Raphael
    Last edited by RS997; 01-24-2020 at 01:34 AM.

  2. #2
    Senior Member oddson's Avatar
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    Are you're sure it's toast...

    A T3.5 should hit the 22 analog signals I see without needing expanders or multiplexers... I think you are one shy for getting them all from the easy edges.

    Do get something working with one pot on a breadboard before you try to wire that up.

    The basics are...

    Potentiometers act as voltage dividers
    ...and provide a DC voltage analog of how far along they are in their range...
    ....which teensy reads as a digital value thousands of times per second....
    ....which isn't as pure and stable as you'd like
    ....so you use some library code to tame it...
    ...and finally scale it to MIDI values and send with another library but this one is but in when you compile as a USB MIDI device.

    There is example code in the Teensyduino download as well as third party libraries that handle most of the details for you.

    You may find your fader-pots are not linear but logarithmic in scale, which is more relevant for audio signals than for MIDI.

    There are workarounds but is it worth it?

    I'm always happy to help but it's not a simple thing.

  3. #3
    Senior Member oddson's Avatar
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    Have you got a gut shot of the controls?

    How they're soldered will tell if you are only using the case.

    If so it could be done with just the Teensy and very careful wiring.
    Last edited by oddson; 01-24-2020 at 03:47 AM.

  4. #4
    A Teensy 3.5 would be exactly what you need to go on without a custom PCB. It has 27 analog inputs, two of them on the two analog outputs, makes 25 analog inputs remaining. One for each pot or fader, plus some extra.
    The analog outputs can be used to control the VU meters.
    The switches go to the digital inputs.
    You will need to cut PCB traces and solder flying wires, but do not exactly need a PCB.

    If the mixer is working, I suggest selling it and buying a ready-made controller. That would make more sense, ecologically and economically, than destroying a working device, so leaving it's footprint but removing it's functionality, and fiddling something without knowledge and uncertain outcome. Also one who buys this thing will not produce another footprint by bying a new one.
    Plus: it is not only the soldering, but also the software, that needs to be worked out.
    Last edited by radias; 01-24-2020 at 06:41 PM. Reason: typo

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