Here's how Emu did it, as near as I can remember from foggy memory. No
resistor network. Keys activate a diode matrix which gets encoded into an
address, which feeds a DAC. Keyboard range is controlled by the gain into
the DAC. Glide circuit (posted on SynthFool) is added after the DAC. Low
note priority only.
Simple and stable!
You can't tune each note individually, but that should be an external module
anyway, like the Moog Scale Programmer.
Moe
> -----Original Message-----
> From: J. Larry Hendry [mailto:jlarryh@...]
> Sent: Tuesday, May 30, 2000 4:39 PM
> To: motm@egroups.com
> Subject: Re: [motm] CV Keyboards
>
>
> OK, I have some comments on this.
>
> 1. I have a keyboard assembly that is brand new that was manufactured for
> a MicroMoog that has the resistor assemblies already installed
> and ready to
> go. I bought the thing for $25. No, I am not selling it. However, I can
> tell you that the accuracy is not very good. I have compared my MicroMoog
> CV output to the Kenton pro-2000 and the Kenton wins, hands down.
>
> 2. I don't see what the big deal would be to make a CV keyboard with each
> note tunable. I think if I were doing it, I would use BOTH fixed and
> variable resistance. As I see it (and please jump in there if you
> disagree) the problem with fixed resistors is exact accuracy. The problem
> with variable resistors is stability and cost. And, you would not want to
> connect variable resistors so that tuning one, changes the total
> resistance
> of the string.
>
> So, I would make my voltage divider with the a fixed resistor and trimmer
> in parallel. Then, this parallel combination would be connected in series
> with as many as I needed for the number of keys I was planning (and maybe
> trimmers on the ends for range). I would plan the voltage at the resistor
> junctions to be about 1/2 way between the voltages I wanted on the keys so
> that the wipers of the trimmers at 50% would be very close. Then each key
> could be individually tuned without effecting the others. I think I would
> make the trimmers multi-turn and of a higher value than the fixed
> resistors.
>
> What I haven't thought out yet is how the divider would connect
> to the keys
> so that you could have a switch between lowest note or highest note
> priority. Or how to make sure that two notes pressed at the same time
> don't short out part of the divider network. I'll have to look at some
> schematics.
>
> Decent trimmers can be purchased in the ~$2 range. So, I don't see why it
> has to be that expensive.
>
> Stooge Larry (who is probably missing the obvious)
>
>
> ----------
> > From: ivancu@...
> > To: motm@egroups.com
> > Subject: [motm] CV Keyboards
> > Date: Tuesday, May 30, 2000 11:10 AM
> >
> > I know this is somewhat silly, but is anyone out there still making a
> > control-voltage keyboard? No, I don't want to use a MIDI
> keyboard with a
>
> > MIDI-to-CV converter.
> >
> > Ivan
> >
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