All Midi to CV interface should have a scaling control for each CV output that can control a VCO's pitch.
This is comparable to the scaling trim pots found inside the Fenix VCO's and VCF's. These may be labeled Scale or Tracking. These controls can either be trim pots or software parameters that can be accessed through menu-buttons. These are used to calibrate the tuning and to compensate for voltage loss in certain setups. Most interfaces have a second trim pot or software parameter called Offset. This transposes the entire range of the CV output You don't need to adjust this Offset for now.
If there are no tuning problems, it is best not to make any adjustments to these controls. If you don't execute the tuning procedure correctly, you may make matters worse.This section assumes that the Fenix VCO's are tuned correctly to 1.00 Volt per octave, and the Fenix mixer modules are calibrated correctly. If this is not the case, adjusting the Midi-interface will compensate the Fenix tuning. This makes it out of tune with all other VCO's. If you can, make a note of the interface settings so you can undo them if needed.Your Midi to CV interface user manual may also contain information about scale calibration or tuning.Some software-controlled Midi interfaces also have a self-tune routine. Run this before making any adjustments.
Adjusting the scaling is very much like tuning the scaling of a VCO. You should take the time to carefully execute each step, especially if you do this for the first time. As always, find a draft-free place and let the instruments warm up for 30 minutes before tuning.You can use a fixed-pitch oscillator such as a digital keyboard (A), or a tuner (B).Connect the (first) CV-out of the interface to CV-1 of the CV Mix 2 module.
The mixer out connects to the CV-1 input of VCO-1.
1 - Play the lowest A on the keyboard, tune the Fenix VCO-1 pitch with its tuning controls.
A If you are using a reference oscillator, set it to approximately 110 Hz, and tune VCO-1 to zero beats.
B If you use a tuner, tune VCO-1 to A=110 Hz.2 - Play one octave higher, and tune the pitch with the scale control of the interface.
A If you are using a reference oscillator, to zero beats.
B If you use a tuner, tune VCO-1 to A=220 Hz.3 - Repeat 1 and 2 until the beats is zero beats in both steps.
4 - Play over a wider range to verify. Adjust when needed.
5 - Repeat with any other interface CV-outputs.
If you don't want to calibrate your midi interface because it is calibrated for use with other instruments and you don't want to adjust the VCO's, you can choose to adjust the CV1 mixer input of one of the Fenix mixer modules.
It isn't designed for this but it is a simple work-around..
Readjusting one of the mixing modules is easy if you have a digital multimeter.
For calibrating the CV1 input you must open up the Fenix. You can use the above sequence, but you adjust the CV1 trim pot instead of the scale or tracking control in step 2.