Dave Peck wrote: ↑Thu Nov 01, 2018 7:41 pm
DISCLAIMER - If you somehow misunderstand these instructions, it won't break anything, but you COULD make it worse, and then you'll need to have someone else do the calibration anyway.
Here's what you do:
In the OSC1 section there is a small round trim pot near the top, to the right of the two frequency sliders. In the OSC 2 section, there are two if these. They may be under small plastic caps. You'll need to remove these caps and access the small trim pots located below the caps, recessed into the metal front panel. These trim pots are tiny 'knobs' that you turn, using a small screwdriver like a jeweler's screwdriver. The purpose of these is to adjust how the osc pitch tracks the keyboard.
1. Turn the synth on and let it warm up for about 20 minutes.
3. Odyssey VCF freq slider all the way up, High pass filter cutoff all the way down, VCA initial gain up, VCO1 sawtooth osc in audio mixer up. Set the octave switch to the middle. Set the VCO1 frequency sliders both to the middle. You should hear a constantly droning sawtooth from osc1, on a mid-range pitch. You should not hear anything else.
4. Play the bottom 'C' on the keyboard and make a note of the exact frequency displayed in your digital tuner.
5. Now play up one octave and note the frequency again. You WANT it to be exactly double the first frequency. That's what you're about to adjust.
6. Make a note of whether this higher octave note is sharp or flat, and then use a small screwdriver to turn the small OCS1 trim pot a little bit. Make a note of which direction you turned it.
Don't try to get the pitch correct at this point, just turn the trim pot a bit (maybe a quarter turn).
7. Now play the bottom key again and note the frequency (it may be a little different now), and play up one octave again and see if the jump is closer to the exact double you are trying to achieve.
8. If it is closer, but still off in the same direction as before (still sharp), turn the trim pot a bit more in the same direction you turned it previously. If it is off, but now it's off in the other direction (i.e. was sharp, is now flat) it means you turned it too much on the previous try and you should turn it part way back again.
9. Go back to step 4 and repeat.
After a couple of tries, you'll have it adjusted so it plays exact octave pitches when you play octaves on the keyboard.
Then shut off the blue OSC1 slider in the audio mixer and turn up the OSC2 slider and do the same, using the OSC2 trim pot.
Note that there is an additional trim pot in OSC2, which is a secondary adjustment for OSC2's tracking when you play two notes at the same time (pressing two keys simultaneously on the Odyseey keyboard causes OSC1 to play the low note and OSC2 to play the high note). Don't adjust this unless you have to.
Let me know how it works!
BTW - you should let the synth warm up for several minutes whenever you turn it on, because the pitch WILL drift during this warm-up period, and the keyboard tracking can be off during this warm up period. This is normal. But after that, it should stay quite stable and you should not have to re-calibrate the trim pots again for a long time, if ever.
as if Korg reproduced it so accurately. 
