AW: Keyboard/Midi Frontend (RE: PolyModular Standards)

[Fraser, Colin J]

> -----Original Message-----
> From: jorgen.bergfors at idg.se [mailto:jorgen.bergfors at idg.se]
> Sent: 07 May 1999 14:15
> To: Juergen.Haible at nbgm.siemens.de; synth-diy at mailhost.bpa.nl
> Subject: Re: AW: Keyboard/Midi Frontend (RE: PolyModular Standards)
> 
> I think it should have at least the following outputs:
> 
> Note CVs for 4 or 8 voices
> Gate for 4 or 8 voices
> Velocity CV for 4 or 8 voices
> 
> CVs for the following continous controllers:
> 
> Pitchbend
> Volume
> Modulation wheel
> Channel aftertouch
> Chorus amount
> Reverb amount
> Breath controller
> 
> Digital signals for:
> 
> Sustain pedal
> some other on/off controllers

If I were building a unit for public consumption, I would design it so that
the builder could add as many cv output demux/cap/buffer and gate output
stages as he wished - the processor should have some way of detecting how
many stages are connected - dip switches maybe.

My own cv converter (also 6502 based - what a chip :-) ) has an octal latch
for the demux channel address - the 3 lowest bits go to the ABC lines on the
4051s, and the upper 5 bits drive the inhibit lines. This gives 40 cv output
channels. 
If I used the 5 lines to drive 74138 address decoders, I could have 256 cv
outputs.
With a lot of lines you start to run into problems with refresh rates, but
who wants 256 cv outputs ?

Colin f