antilog

[Paul Maddox]

Paul,

> yeah, this is the 'exponential' cell.
>

thought so, but thought Id best check before I speant ages playing with
taylor siers and lookup tables
and then discovering started off totally wrong!

> I've been interested for a while in the possibility of making an
exponential
> convertor using a micro, and multiplexing it, so that all the problems of
stability in
> the expo cells would be a thing of the past.
> But, i'm not a programmer.

Im hopeing to use this for converting PITCHwheel information via midi.
But have plans for a wavetables VCO using a phase accumulator oscillator
and an AD and doing the log function in the micro.

> I know 12 bits would be enough, though 16 bit serial D to A convertors are
> cheapest.
> (Though not guaranteed for DC, I have never had trouble with them).
>

12bits for AD would be more than enough.. 4bits at the top for the octave
(16 octaves) and 8 bits for spread over 1v for resolution of octave, which
should be fine.

I also have a realy nice thought for a fully programmable digital modular
synth.
Basically each module has a micro, with a few ADs and some DAs.

now the module itself is analog (VCF, VCA, ring mod, etc) but the signals
being passed
to it are in digital format, they're converted to Analog, processed then
converted back.
A common BUS system between all the modules and a main CPU module
controlling the whole
thing.. VGA display output and heres the really sexy part, instead of patch
sockets you use
momentary switchs.. when you hold down a switch (say VCO output) you then
press another
switch whilst holding the source switch down and select which input it goes
to (say VCF input).
Then when you want to see which is connected to whihc you hold down either
of the switchs
and the LED on the other end of the virtual lead (next to the switch) lights
up and the same
happens on the VGA display. The CPU module would route all the Digital
signals between the
modules and enable the modules to be fully prgammable.
To add more modules, simply power off, plug in your new module and power on.
the CPU will scan
the modules and show a picture on the display of what modules you have.

What do you reckon?
This is a back burner project at the moment, I'll start it in earnest when
Ive done my polywave.

Paul MADdox
________________________________________
Modulus Synthesiser Website;-
    Http://www.noxons.ision.co.uk/