[sdiy] Velocity Sensitivity Retrofit

[Veronica Merryfield]

They time the breaking of a switch to the making. With a CV based  
keyboard, I would use an extra switch and use that as the timer. You  
could even do this analoguely if you wanted, but it is easier to do it  
digitally.

The transcendent polysynth (Tim Orr) used a logic chp scheme and  
memory - once a contract broke, a corresponding word in a memory was  
preloaded and then decremented each time round an address loop. The  
decing stopped at zero or the contacting making and this value  
outputted to a DAC and S&H to be used in the voice. If you were doing  
a monosynth, you could use a capacitor that is charged initially and  
discharges once the contact is broken until it is made at which point  
the voltage is sampled, thus there would be a cap and parrallel  
resistor per key but the rest happens on the buss bars. Arrange the  
contact to make before the CV contact makes. You'd probably need a  
gate too to cover for a very slow key press and nothing on the cap.

Just my 2pw

Vrnc


On 27-Feb-08, at 10:17 PM, Kyle Stephens wrote:
> Out of idle curiosity, has anyone tried cannibalizing
> an otherwise stock, non-MIDI keyboard and making it a
> CV interface *with* velocity sensitivity?
>
> I'd imagine accelerometers would seem to be the way to
> go for achieving the later bit. I haven't ever poked
> under the hood of a MIDI keyboard with this in mind to
> see exactly how its done there though.
>
>
>       
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