Moog Music Forum

Hi,

I’m new to the world of Moog and modular and I’m having an issue with calibrating the VCO of the Mavis.

I’m using a Keystep to gate and provide 1V/Oct to the Mavis, with a digital tuner patched into the audio output of the Mavis.

The Keystep also triggers an audible sine from a second (digital) source.

My issue is that an octave on the Mavis doesn’t appear to be ‘wide’ enough. Where if you tune the Mavis to middle C, an octave above that is a little flat.

If I then adjust the calibration to account for this and dial in the C above middle C, middle C becomes sharp!

Moog documentation says to avoid using the internal calibration and to only calibrate the Mavis when necessary, so I don’t want to mess this up by blindly fiddling around.

For info, the internal calibration is set around its midway point and the Mavis was in an initialized state.

The calibration procedure for the Werkstatt worked the same for the Mavis.

Note: This was done while Mavis was in an initialised setting (pitch knob at 12 o clock).

1. Determine 0 Volts on your controller, for my Keystep it was C-2. This can be confirmed by the pitch remaining constant while you adjust the Pitch Calibration screw.

2. Dial in the correct pitch (C in this case) using a tuner and the pitch control on the front panel.

3. Shift a few/several octaves up on your controller, play the same C and adjust the Pitch Calibration screw until the tuner shows a C.

You can confirm the above steps by playing C’s between those in steps 1 & 3 to finesse your results.

Video description here…
https://youtu.be/vVNI3jibZ4U

Welcome to the world of Moog and Modular! Calibrating a VCO can be a bit tricky, but with a bit of patience and persistence, you should be able to get it working correctly.

It sounds like you're on the right track with using a digital tuner to help with the calibration process. When you say that an octave on the Mavis doesn't appear to be 'wide' enough, it could be an issue with the tuning of the VCO. If the VCO isn't properly tuned, the octave might not sound correct.

gr00veh0lmes wrote: ↑Tue Aug 30, 2022 3:00 am My issue is that an octave on the Mavis doesn’t appear to be ‘wide’ enough. Where if you tune the Mavis to middle C, an octave above that is a little flat.

If I then adjust the calibration to account for this and dial in the C above middle C, middle C becomes sharp!

It sounds like you are on the right track. You may be missing the point that VCO calibration is an iterative process — the two knobs (fine-tuning and scale-tracking) interact with each other. You have to fine-tune a “low-C”, then play a “high-C” and adjust the VCO tracking trimmer. Then, you have to repeat: tune the lower-C with the fine-tuning control and high-C with the scale trimmer. This should be repeated until the process converges and no further adjustments are necessary.