Tuning Your ACXsynth MIDI2CV
In order to achieve accurate CV conversion, it is necessary to tune your MIDI2CV module once you are
finished building it. In order to accurately tune the module, you will need a decent multimeter. A $10
multimeter will not yield perfectly accurate results. Spend $100 on a decent quality meter and you
will be very happy you did (not just for this project, but for others as well).
Tuning the module is quite easy. Just follow these steps:
1.) Plug the module into your system, turn it on and let it warm up for 30 minutes.
2.) Make sure the module is in MIDI learn mode by quickly resetting the power to your system. Don’t
press any keys on your MIDI controller yet or send any SYNC data to the module via MIDI.
3.) Plug your multimeter into each CV output and tune the OPAMP TUNING trim potentiometer for
the CV output you are tuning so that the respective CV output reads as close to 0.000V as possible. If
you cannot get to 0.000V, it’s probably because you did not listen to me and
used CA3140
A
EZ opamps
instead of CA3140EZ
like I said to use in the Bill of Materials!
4.) Now, plug in your MIDI keyboard and tune the CV outputs for V/oct scaling. Plug a CV output into a
VCO in your system and either:
Read the frequency of the VCO and adjust for v/oct
or
Read the voltage out of the CV output of the MIDI2CV module and adjust for v/oct.
I like the second method, myself.
Whatever method you choose, you tune the CV output by stepping up and down octaves on your
keyboard and verifying that the voltage/frequency has doubled each octave you step up.
Whichever method works best for you is the one you should use!
Your MIDI2CV is now setup and ready to use!
