Installing Syntaur's Arp Odyssey Sub-Oscillator Kit

Important Disclaimer: You are solely responsible for any damages, problems, or injuries resulting from opening up and working on your equipment. Unless otherwise indicated, the equipment should be powered off and unplugged while these procedures are being done; otherwise, you can be exposed to potentially fatal voltages. If you do not feel comfortable or competent in performing these tasks, we strongly recommend taking your equipment to a qualified service center.

Limitation of Remedies: Syntaur Productions is not liable for any direct, indirect, consequential or incidental damages arising out of the use or inability to use this product. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages, so the above limitations may not apply.

Tools needed:
Phillips-head screwdriver
¼-inch nut driver
Drill with 1/8-inch and 9/32-inch bits
Soldering iron and solder

The wiring from the sub-oscillator board is color-coded as follows:
Red: 15-volt input to sub-oscillator board
Green: Ground
Brown: Signal from Osc 1
Purple: Signal from Osc 2
Black: Output from sub-oscillators


1. Remove slider caps from both VCO sections, and the LFO and S/H section. You may want to take a photo of the unit first, to get the colored caps back in their original configuration once you are putting everything back together.

2. With the synthesizer unplugged, remove all of the screws that go through the plastic tray that forms the bottom and sides of the synth. These consist of three screws on each side, four screws on the bottom panel, and four rubber feet with screws on the bottom panel.

3. With these screws removed, the entire synthesizer and keybed will come free from the plastic tray. You can now lay the synth face-down on a padded work surface, with the keys facing you, and set the plastic tray aside.

PCBs 4. It is a good idea at this point to mark the wiring connectors and the circuit board they plug into with a Sharpie, to avoid any confusion as to what wiring plugs where, and in what direction the connector should be. A reference photo of the inside of the unit can be helpful as well. There are three circuit boards secured to the top panel. From left to right, they are Board C, Board B, and Board A, and the Interconnect Board connects the three together.
Interconnect Board 5. Remove the Interconnect Board (see photo at left), by pulling it upward, away from the circuit boards underneath it. It will simply slide up and off of the connector pins.
Remove Keybed 6. Remove the keybed, first by unplugging the wiring connector that runs to Board A, then by removing the four screws that secure the keybed (two on each end) with a ¼-inch nut driver. Set the keybed aside, being careful not to bend any of the J-wires underneath each key.


7. Slide off the two wiring connectors from Board B (the center board), then remove the 5 screws that secure that board to the top panel (one screw in each corner, plus one in the middle). Remove Board B and set it aside.


Mark Holes 8. On the inside of the metal panel, mark the position of the holes to be drilled for the potentiometers. Use the two rectangular slide switch holes (the Audio and Sync switches) at the top of each VCO section for reference. With a sharp pencil, first draw a line extending from the center of each of these holes, as pictured. Then, place a cross mark on each of these lines 1.25 inch from the edge of the slide switch hole.
Pilot Holes 9. Drill a pilot hole at each cross mark with an 1/8-inch drill bit. Be careful to keep the bit exactly on the cross mark when starting to drill – don’t let it ‘walk’ off target, or your potentiometers will not end up perfectly aligned.


10. Once the pilot holes are drilled, drill the holes out larger using the 9/32-inch bit.

Standoff 11. Remove the mounting screw from the back right corner of Board C, and replace it with the standoff from the kit (see photo).
Pots Mounted 12. Mount the potentiometers onto the front panel now. Leave one nut on each potentiometer (screwed all the way down), then position the pot in the hole, and secure the pot with a washer and nut on the top side of the panel. Make sure that the pots are positioned so that the wires point toward the keybed. The pot with the longest wiring (blue, yellow, and green wires) goes into the hole for VCO1, the pot with the shorter wiring is for VCO2.


13. Reinstall Board B back into the Odyssey. Make sure the wiring to the pots does not interfere with the sliders or switches; the wiring can be taped to the metal panel if necessary.

PCB Mounted 14. With a single screw, mount the sub-oscillator circuit board onto the standoff installed in Board C (from Step 11).
Black Wire 15. Solder the black wire from the sub-oscillator board to Board C as shown here; this is the sub-oscillator output.
Overall Wiring 16. The remaining wires attach to Board B as shown. Solder the green ground wire to trim pot R104 on Board B, as shown at left and in the next photo.
Red and Green Wires 17. Solder the red wire (voltage feed to the sub-oscillator board) to R38 on Board B.
Purple and Brown Wires 18. Solder the purple and brown wires (oscillator signals to the sub-oscillator board) to the points shown around chip Z4 on Board B. The brown wire connects to pin 3 (which also connects to pin 5), and the purple wire connects to pin 11 (which also connects to pin 8).


19. Reinstall the interconnect board, making sure that every pin goes into its socket – it is easy to get it misaligned, with pins missing the connectors.


20. Turn the Odyssey back over, plug it in, and turn on the power. Be very careful, as the power supply wiring will be exposed and can be dangerous or fatal to touch! Turn up the VCA Gain slider, and you should be able to hear each sub-oscillator by turning up the new pots. Once the circuit is confirmed working, unplug the power, and turn the Odyssey back over.

Finished Odyssey 21. Replace the keybed – and don’t forget to plug the wiring harness back to Board A!


22. Replace the bottom plastic tray of the synthesizer, reinstalling the rubber feet, the bottom screws, and the side panel screws.


23. Press the knobs onto the sub-oscillator pots, and replace the slider caps, and you are ready to start wobbling the windows with low end!