arp trig/gate idea problem..

[Stopp,Gene]

Rob,

I think your first approach is OK and something was wrong somewhere....
the PS in the Odyssey should power a couple extra op-amps no problem.
Heaven knows I've hacked up a few before. The gate input may even handle
5 volts as it is (I can't remember) and if not, the noninverting op-amp
with a gain of 2 should work there. As for the trigger, I think you can
just stick a cap (like 0.1 uF) from the gate to the trigger. I take it
you're adding external control to an Odyssey that does not have input
jacks? Maybe I can dredge up my old schematics. Might take a while. Or,
if somebody knows where the schemos are on the web, I can take a look
there. I could tell you in a minute if the drawings were in front of me.

 - Gene

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From: cyborg0 at GlobalEyes.net
To: synth-diy
Subject: arp trig/gate idea problem..
Date: Tuesday, February 17, 1998 10:13PM

Hi all..
Ok, as we all know, the arp trig/gate is somewhat troublesome to us
individuals who have single channel 5V midi/cv gates... Heres what I was
trying to do, and I thought perhaps maybe someone came up with a mod or
something for the Arp Odyssey to solve this dillemma..
Ok, I tried to use a noninverting opamp to change the voltage from 5v to
10v, then, I took the 10v output and used a differentiator opamp
configuration to get the trigger pulse. The normal 10v pulse went to the
gate, and the differentiator went to the trig..
All was fine, until I realized that the internal PS in the Odyssey
couldnt supply the current for the two opamps! The supply line voltage
went from 15+- to about 10v+-!!.
So, for now, that rules out using this configuration and being able to
keep the whole mod internal..

Next, i thought that perhaps I could put the input of the 5v gate signal
to the base of a jfet, optoisolator, or a 4066 bilateral switch which is
across the gate/trig contacts and trick the Oddy into thinking i was
pressing a key to trigger the gate/adsr. I think this may be the easiest
way, but..
when i tried this trick, it seemed like the CV wants to drift!
Anyone know of a way around this??
Another thing: anyone know what the on state resistance is in a 4066??

rob