Rare Waves LLC
Grendel RA-9 Grenadier
User Guide 1.3
© 2015
r a r e w a v e s . n e t
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SEQ DRONE FADE
REPEAT PROG
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VDC
VCO Tuning Method # 3 - Using a voltmeter, MIDI-CV converter, and A-440 tone source
This is a fast and accurate way to tune the VCO when you have a MIDI workstation and MIDI-CV
converter. It requires a digital voltmeter and a tuner with A440 tone output. The results will be in tune
regardless of any 1V/octave scale inaccuracy within your MIDI-CV converter.
Getting ready
Ÿ
Power on the Grenadier for 30 minutes before beginning the procedure.
Ÿ
Locate a small screwdriver suitable for adjusting the Grenadier’s TUNE and VCO trimmers.
Ÿ
Locate a digital volt meter (DMM) with 3.5 digits precision or better. Connect the DMM to the
MIDI-CV converter’s CV output. You can use a pair of alligator clips to make connection between
the DMM’s test probes and a patch cable. Connect the DMM’s red probe to the patch cable’s tip,
and the black probe to the patch cable sleeve.
Ÿ
Turn DRONE on. All other switches should be off, including PITCH ENV. Set LFO DEPTH to
zero (12 o’clock). The Grenadier should be sounding a steady tone without modulation.
Ÿ
Give the Grenadier’s TUNE and VCO trimmers some exercise for cleaning purposes. Do this by
rotating them from one end to the other two or three times. These are single turn trimmers.
Procedure
1. Find the key on your MIDI controller which produces an reading of 2.270 volts DC on the
voltmeter.
If it doesn’t read exactly 2.270 volts, select the key that is approximately closest.
Remember this key - it is your reference note.
2. Disconnect the voltmeter from the MIDI-CV converter.
3. Patch the MIDI-CV converter to the Grenadier’s CV IN. Play the reference note on the MIDI
controller.
4. Listen to the A-440 tone from your tuner and compare it to the Grenadier’s pitch.
5. Adjust the TUNE trimmer so the Grenadier’s pitch sounds exactly 2 octaves below A-440 Hz.
6. On your MIDI controller, now play the key that is located 2 octaves above the reference note.
7. Adjust the VCO trimmer so the Grenadier’s pitch is in unison with the A-440 tone.
Note that this procedure works because at 2.270 volts, the VCO’s pitch is independent of the
VCO trimmer setting.
If you have a frequency counter in your modular setup, you can skip listening to the A440 tone
reference. Connect OSC OUT to the frequency counter’s input. Use the frequency counter to
find your target of 110 Hz at step 5, and 440 Hz in step 7... fast, silent, accurate tuning.
Final adjustment
8. Play an “A” note on your MIDI controller. Compare the Grenadier’s pitch to the A-440 tone.
9. Adjust the TUNE trimmer so the Grenadier is playing a pitch of A in unison (or perfect octave
interval).
If you practice this procedure several times it will become a painless and intuitive way to put the
Grenadier in tune with your other instruments at the beginning of a session.
Hint: If you remember the reference note for 2.270 volts output from your MIDI-CV converter, you
can begin at step 3 next time - and you won’t need the voltmeter any more.
SET TO 440 HZ
SET TO 110 Hz
MIDI-CV
CONVERTER
CV OUT
VDC
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