ARP Odyssey AR Hacked

[|||| Philip Pilgrim ||||]

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 :)

enjoy!
Philip

-- 
Philip Pilgrim               The Lab
5 Evan's Drive               synth mods, software development
Hammond's Plains             digital audio recording/mastering
Nova Scotia, Canada          music architecture/construction
B4B 1M8
(902) 835-7844

           Home of NovaMod, UP and Microwave tools

           web page: http://www.robotnik.com/the_lab
           email:    mailto:thelab at sprint.ca
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