Alternative to MIDI-CV

Erik The ViKing E.G.P.Schuijers at stud.tue.nl
Wed Feb 14 19:20:18 CET 1996


In message Wed, 14 Feb 96 09:07:38 PDT, gstopp at fibermux.com  writes:

> Response to all the recent posts...
>
> It's true that a discrete 16-bit R-2R ladder has the LSB "down in the
> mud", both from noise and component tolerance aspects.

You've got to be kidding me: a 16-bit R-2R ladder.... do you know which
tolerance these resistors should have???

> As for my recent 16-bit R-2R ladder for the freq-voltage converter
> experiment - it was just for kicks, really, as long as the bits were
> there I thought I would throw them into the sum just to "sway the
> noise a little". I then took Don Till's advice and tried the
> exponential-discharge capacitor into a sample & hold idea. It looks
> good on the scope, but I had trouble trying to get it to convert at 1
> volt per octave using scope period measurement and a DVM. I probably
> would have had better luck listening to a VCO while tweaking the
> converter gain. Heck, as is it may be better than that goofy Korg
> MS-20 pitch follower...
>

So my Korg isn't broke.... it's just worthless!!

> Next I thought of an "exponentially discharging digital counter", in
> which the 16-bit down-counter modifies its own clock in such a way
> that the frequency division modulo is increased as the count
> decreases. Now when the external input frequency transitions latch in
> the period measurements, they will be at 1 volt per octave already (if
> the counter modulo math is correct). Of course it's always possible to
> have the period measurement value point to an address in a look-up
> table, whose data value goes to the CV DAC. While this may seem
> inelegant it will certainly work, but now we're getting into PROM
> programming again.

I had a simular idea in regard to the (E)PROMming part but I just have one
advice: DON'T!! It's going to get so sloppy you don't even want to think
about it. There are some easier ways of getting more control!!!

Erik The ViKing
ViKingdom Comes



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