[sdiy] Chaotic/lo-fi patching techniques

[Ullrich Peter]

Hi!

>For a more integrated approach, how about using one of these:
>
>http://www.analog.com/en/prod/0%2C2877%2CAD8113%2C00.html
>
>AD8113 16x16 crosspoint switch with a SPI input for controlling the
>selections. Just hook up your favorite microcontroller to randomly
>generate switch configurations. Main downside is that you can't drive
>one output with multiple inputs - it's a 1:1 hookup only. Might not be
>quite as whacky as what randomly shorting outputs together will do...

You can simply turn it into a mixer by adding summing resistors on the
inputs and adding inverting opamps on the outputs.
So each output of the matrix is the summing point of the summing amp
made with the inverting opamp on the output.

Works fine - I built this with the Mitel/Zarlink MT8816 and also with
the MT8812 parts.

The can be used for static signals, MIDI, Audio and up to video signals.

I also used this parts fpr universal MIDI interfaces where these matrix
circuits sit in parallel with the keyboard matrix. Not a cheap solution as
you need I think 4 of the MT8816 because you have to add decoupling
diodes. But for me it was OK because I had a few dozen of these chips...
My Korg Poly61 MIDI interface works with these chips...

For the Casio SK1 I used the MT8812 chip but without the complete
decoupling - so the polyphony via the MIDI interface is limited to 2.
One year after I built it I found a nicer solution someone built where a
microcontroller scanned the keyboard rows and generated the column
signals at the right moment to simulte a keypress. This solution need no
decoupling diodes but has full polyphony...

Ciao
Peter

http://www.ullrich.at.tt