midiDAC firmware... long reply

[Tony Allgood]

>Wonder where he makes them for such a low price...

Thanks Mikko, I'm glad you liked them. They are made in Cockermouth,
Cumbria by a company called 'New Resolution Circuits' Very nice people
to deal with.

>So a MIDI CV converter with 8 outputs could control 8 CV controllable
units, like for VCO only one CV is needed.

A basic voice needs at least gate and CV. But for all my synths I need
velocity as well. And aftertouch is very useful to raise filter freq.
for example. The modulation depth CV is very useful. You can use to
introduce pitch mod, where a software LFO could indeed modulate the
pitch CV directly. But with an open system of multiple CVs, you could
control the pitch of VCO2 only, which in turn is synched to VCO1. A VCO
may also require PWM inputs or even sync depth. A decent midi-CV
convertor should have enough CVs to control all of these. Pitch bend and
pitch addition could be implemented in software but that would need a
16bit DAC. Although these are cheapish, the PIC we used cannot access
that amount of lines. Serial DACs are an option, but to get fast s/h
update times, this would be quite a challenge with a simple PIC. I have
decided to add the analogue CVs from the two sets of 7-bit CVs. This way
you can set the pitch bend depth with one pot. Simple.

The midiDAC is designed for monosynths/modulars only. It is not for
polyphonics, it was never designed to do that. The Kenton Pro-4 is able
to access four polyphonic voices all with velocity. But you need three
signal lines for every synth voice. Its now getting hairy for an
external convertor. In the UK the Pro-4 costs about 500UKP. Ten times
the price of the midiDAC, albeit unbuilt.

As for digital LFOs. Well, I like knobs. I do not want to have to access
some menu to have to double to speed of my LFOs. I want to turn a knob.
Its instant. The LFOs/ADSRs on my Prologue and Kenton never get used,
because its a pain to change them. Perhaps there is a real need for an
analogue interface in a midi-CV convertor, with CV outputs that control
the individual modules of a synth, much like the modulation routings of
a D-50. It would have CV outputs for VCO, VCF and VCA.

But then why not just have separate outputs for velocity, pitch etc and
do the routing by patch cable or internal wiring inside the synth. I
would say that allowing the user to choose patches is better than to
provide complex and expensive convertors, which use features that are
too cumbersome to use.

PS. My spellchecker which I used to check this document said that
'cheapish' should be spelt 'teapot' Well, it made me laugh!

Regards,

Tony Allgood  Penrith, Cumbria, UK

MidiDAC midi-cv, SuperLadder, TB303 clone and Filter Rack

http://www.techrepairs.freeserve.co.uk/projects.htm