[sdiy] Gate from pitch change

[Fredrik Carlqvist]

Have you tried a pull-down resistor load on the VCA CV output? Maybe
it's an open collector output or something like that. Seems strange to
provide a CV out that cannot be used for anything interesting?


Fredrik C
 

-----Original Message-----
From: owner-synth-diy at dropmix.xs4all.nl
[mailto:owner-synth-diy at dropmix.xs4all.nl] On Behalf Of Karl Ekdahl
Sent: den 3 maj 2006 05:15
To: synth-diy at dropmix.xs4all.nl
Subject: [sdiy] Gate from pitch change

Hi list, i'm hacking up an old Casio and need to get a gate signal to
control an ADSR. 

The keyboard has both VCA CV output (and obviously a
VCA!) and a squarewave output, both which decays a couple of 100 ms
after key release which makes them unusable as direct ADSR gate. The
only feasible way that i can think of to get a working gate out of this
would be to detect pitch changes but i'm not sure on how to implement
this. 

I'm thinking of a Voltage to frequency converter
(LPF?) a S&H and a comparator but that seems unnecessarily complicated. 

Either way a pitch-change detector would only generate a new gate signal
if a new key is pressed but i guess i'll have to live with that.

Any ideas would be appreciated!

Karl