ARP Odyssey AR Hacked

[Rob]

|||| Philip Pilgrim |||| wrote:
> 
> Hi all,
> 
> I used the simple Arp AR envelope from the Odyssey in my SH-101 NovaMod
> upgrade (due to it's simplicity) but was never really satisfied with it.
> The main problem was that the envelope could not be re-triggered by a
> new key press thus it had a portamento-ish amplitude slurring.
> 
> A few people on this list requested that I update them if I ever figured
> out how to re-trigger the env....well here it is:
> 
> I finally had a chance to hack the circuit in my typical crude but
> usually functional fashion and found that by adding a resistor and
> transistor, the circuit could now accept a re-trigger signal. I never
> checked to see if the odyssey had an available trigger signal however
> the SH-101 has a hi to low transition trigger which I used (found at R36
> on synth board btw).
> 
> The attached AR circuit (re-annotated from the Odyssey values) has the
> two new parts R7 and Q3 added. It is obvious that the negative
> trigger-in switches the transistor Q3 and drains the charge on the cap
> C2 thus resetting the output to 0V.
> 
> For positive pulse triggers simply use a NPN (2N5172).
> 
> Finally the attack and decay times can be increased by increasing the
> value of C2. I experimented last evening and found 4.7uf very useful.
> 
> All of these improvements should be easy to do on an odyssey from the
> solder side of the board :)
> 
hohoooo! nifty! The Oddy always sounded less that crisp due to this
non-retriggerability..
Rob