Odyssey, breakout box

Moving on with the Odyssey mods..

I wanted to add CV/Gate I/O to the Odyssey without drilling the enclosure (reversible modding FTW). No choice but to make the mods external, maybe route some other signals as well.. As you probably guessed already, here’s where my Breakout Box comes into play!

Looking around the net I found some old posts where Gene Stopp had provided his solution, so I took that as a starting point. For the interconnect between the box and Odyssey, I cut up a old 25-pin DSUB extension cable. No need to solder connectors and the cable fit neatly through one of the jack holes on the rear. Who needs a sustain pedal anyway ;).. Here’s the schematic for the Breakout Box:

Can't see shit? Click image to download pdf.

For the casing I picked this old plastic project box I had lying around. It somewhat matched the main colors of a whiteface Odyssey so in that sense it was a rather obvious choice.

The gate-to-trigger converter is a near-direct copy from the Odyssey schematics (MKII & MKIII models), except that some irrelevant parts (not needed in my application) are omitted and the PNP transistors have been replaced with generic BC557s. Since these are used in switching configuration, I figured the resistor values don’t need to be re-calculated. Probably sth like 2N3906 would do just as fine. However, BC557 seemed to somewhat match at least some of the values of 2N6076, so I went with that.

All inputs have a zener diode guarding against overvoltage conditions; I’m not sure how sensitive the Odyssey might be to overvoltage, but given the fact that zeners are a really cheap way of adding safe-guard, it’s not like you go bankrupt at least for tossing a few of them into the circuit. They could be replaced with slightly higher (max. +15VDC) or lower values, or also just left out.

Outputs are impedance buffered with opamp followers. LFO / Noise output signals (triangle/sine and pink/whitenoise respectively) have to be selected with a toggle switch. They’re there just because the enclosure I chose couldn’t fit more than nine output jacks. As there are a few unused opamps in the design, these switched signals could’ve been routed to individual outs had there been more room. Maybe I could’ve also used 1/8″ jacks..

How many 1/4" jacks can you squeeze in..

I also added a Gate Out voltage selection switch and a button for triggering gate. The voltage selection switch toggles between +12V and whatever is the onboard trimmer R9 is calibrated to (I set it for +5V gate). R10 is calibrated for 12V.

Just in case you’re wondering about a few things on the schematic.. For some reason unknown, the design program wants to add a “-12” label to the negative voltage rail although the net has been defined as “-15” in the settings. Don’t know why, it just does that.

Also, the program doesn’t have a proper decal for switched jacks in its default library. Knowing I’m not going to etch a board for this project, I didn’t bother drawing one either. So, S3 simply represents the switching option of the jack. It’s there because I wasn’t sure whether the Odyssey can handle two sources driving the CV bus. Adding a summing CV mixer would’ve been one option, but constructing the stripboard was just easier this way.

All wired up and ready for testing.

If the Breakout Box is not connected, the ODY_GATE_BUS and ODY_GATE_OUT pins need to be short-circuited from the connector on the Odyssey-side for normal operation. If you built this box for yourself without reading this far, I hope you installed the female connector on the Odyssey side ;).

Questions / comment / improvements welcome, just leave a comment!


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One response to “Odyssey, breakout box”

  1. arto says :

    Come to think of it, maybe there should be a picture of what the box looks like on the outside.. :)


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