Hi, this video is about how to calibrate the Odyssey’s VCO’s pitch and scaling.
The procedure is from the Original Arp Odyssey service manual,
and is the same for all Arp, Korg and Behringer Odyssey’s.
The trimpots will however have different names depending on who’s the manufacturer.
In this video I’ve used a Behringer Odyssey, and therefore I will be using the Behringer names.
But I will also show the Arp names on the screen.
It would be a good idea to check the voltages in the power supply first, otherwise you’ll have a really hard time calibrating.
The internal voltages in the Odyssey has to be exactly plus and minus 15.00 volts.
I’ve made a video on how to open up the Behringer and adjust the voltages.
There’s a link at the top of the screen and I'll leave a link in the description.
First set the Odyssey’s all front panel sliders at their minimum positions.
Set the VCF FREQUENCY and VCA GAIN at their maximum positions.
Set VCO 1 waveform to Square Wave
Set the VCO 1 Volume to max in the AUDIO MIXER
Put the VCO 1 range switch in the KYBD ON position.
Put the VCO 2 SYNC switch in the OFF position
Make sure the Transpose switch is in the NORMAL position.
Monitor the output of the Odyssey with a frequency counter, like an oscilloscope or a multimeter.
This first step is just to check that the VCO’s are approximately at a correct value at low frequencies.
Put the VCO 1 COURSE slider DOWN fully.
Put the VCO 1 FINE TUNE slider exactly in the MIDDLE.
Press the lowest C on the keyboard.
Your frequency counter should read 20 Hz.
If It’s far off you’ll have to open the synth and adjust the VCO1 OFFSET trimmer to get the 20 Hz.
Mine was good so I didn’t have to do that.
With the lowest key on the keyboard still sounding,
adjust the VCO 1 COURSE FREQUENCY slider for exactly 100 Hz on the frequency counter.
Press the highest C on the keyboard.
Turn VCO 1 SCALE trimmer to adjust the frequency to exactly 800Hz.
Use a small screwdriver.
Repeat the calibration process until you measure exactly 100 Hz on the lowest C and 800 Hz on the highest C.
Mine was bang on at the first go. But I've found that it usually takes several attempts before it's perfect.
When the scaling of the first oscillator is perfect, repeat the process for VCO 2.
I prefer to do it by ear with both the VCO 1 and 2 at the maximum volume in the AUDIO MIXER.
Set VCO 2 waveform to Square Wave.
Press the lowest C on the Keyboard.
Raise the volume of VCO 2, you can now hear both the oscillators.
Adjust VCO 2 COURSE FREQUENCY slider for exactly 100 Hz.
Press the highest C on the keyboard.
Using the VCO 2 SCALE trimmer adjust the frequency of to exactly 800Hz.
Go back and forth until you have a perfect 100 to 800 Hz interval.
Next, make sure that no patch cables are attached to the CV, GATE and TRIG jacks,
and that ODYSSEY is working in Duophonic mode.
Set the VCO 1 to minimum volume and VCO 2 to maximum volume in the AUDIO MIXER.
If you duophonicaly play two notes on the keyboard, only the highest note will sound.
Press and hold the highest C down on the keyboard, then press and release the lowest C, still holding the highest C down.
There should be no change in pitch of VCO 2 when the lowest note is pressed.
Adjust the VCO 2 SCALE 2 trimmer until there is no change in pitch when the lowest note is pressed.
That’s it. Now your Odyssey should play in pitch all over the keyboard.
