E:pp:ik wrote:Thanks Teach! I'll have to dig around and find a way to convert this. I think the Octave Cat is a similar situation.
E:pp:ik, I think this is the circuit you want, it will certainly do the job:
It's a common CV mixer circuit that appears just about anywhere there are multiple CV inputs into a circuit. Build the portion inside the red box, with a couple changes.
It MUST be powered from the ARP, or with an external power supply, using the +15V and -15V rails (±12V may work fine as well) to power the opamp. Obviously, using the ARP power supply will be cheaper. The KOV/ECV switch is not necessary, just use whichever input jack you favor. At any rate, that input is the one to use coming from the x0x. The bottom of the pot marked P8 (Frequency) in the schematic MUST be connected to the -15V rail, not ground. The circuit will not be able to take the x0x CV out to 0V otherwise. P8 can be a normal pot, or a trimpot, your choice. This pot will now function as your "zero adjust" pot. Have the x0x output its CV for its lowest note, and adjust P8 until the output of A3 is 0V.
The V/Oct trimpot (P3) and R17 are optional, and probably redundant. You can just take the output off the opamp. You should be able to use just about any dual-supply opamp you like in this circuit, as TL074 would be a waste of 3 other opamps.
All this could be built in a small box. I would still recommend running wires out of the Odyssey to power it, ±15V is all you'll need, the signal cables will take care of ground.
If you don't mind modifying the Odyssey, you should be able to build this circuit on a tiny "daughter board", and connect the CV input directly to the Odyssey's CV input jack. The the wire formerly connected to the "tip" contact of the Odyssey's CV input jack and connect it to the output of the opamp. If you choose to use a trimpot for P8, you will not need to drill any holes in the Odyssey's case. WARNING: Doing this will make it difficult to use any other analog synth's CV out to control the Odyssey, as it will need to be re-tuned for the output of the opamp to equal 0V. You may be able to get by with using the tuning knob on the Odyssey, or you can add a normal pot to the back of the synth for P8. You could also add an additional CV input jack for this circuit and, via a switch, connect the output to the "tip" connection of the factory CV input jack. The switch will allow you to turn the "x0x CV in" input off, so that no knob twiddling is necessary when not using the x0x.
I hope you find this useful!
Don Taylor, a.k.a. Brassteacher
"Jack of all trades, master of none, proficient at even fewer..."