MRG Onde Tuning Guide

1CV/Octave Fine Tuning

This is a classical CEM 3340 tuning. There are two trimmers in this scheme: SCALE ADJ and HFT ADJ.

SCALE ADJ regulates the overall 1V/O tracking of the IC. HFT ADJ is used to help at high octaves.

We will set a low base frequency. We then tune the first two/three octaves with SCALE ADJ, then switch to higher octaves and trim HFT ADJ.

Step T1: 1V/Oct CV tuning

Set the base frequency of the Onde to a low audible frequency (e.g. 100Hz).

  1. Connect a keyboard to the CV input of the module (most likely through a MIDI to CV module).
  2. Keep going back and forth between the lowest C key of the keyboard and the next C one octave up, adjusting the SCALE ADJ trimmer until the output is tuned: i.e., the higher C has double the frequency of the lower. This can be done through an oscilloscope or by ear.
  3. Then go up one octave, starting from the previous step’s higher C as the lowest and adjust the SCALE ADJ trimmer until the frequency doubles.

Once the Onde can track easily two octaves, you can check the higher octaves. You will notice that after the third or the fourth octave the frequency doubling will become less and less precise.

This will be sorted by working on the HFT ADJ trimmer.

Step T2: High Frequency Tracking

Check that between the fourth and the fifth octave the frequency double. If it doesn’t, change HFT ADJ until it does.

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