trying to make my Arturia Beatstep Pro control my Volca Modular. I've attenuated the GATE signal (13V from the Arturia down to 6.5V) to make it less aggressive on the Volca, and this works fine.
The problem is with pitch. I've made measurments, and the output voltages form the Arturia are perfect, nice clean 1V/octave, with 0V for note C2 to 6V for C8. But the Volca behaves strangely, pitchwise. I've hooked up my oscilloscope to the headphones port of the Volca to check the various frequencies of C notes when pitch is controlled by the Beatstep Pro. Turns out there's a slight base offset plus a non-linear drift.
My test goes like this:
- • I have the Beatstep Pro turned on, and play a test pattern of C notes all tied together to get constant pitch output (again, calibrated digital multimeter shows perfect output voltages here)
• A modified TRS mini jack runs from the CV pitch output of the Beatstep to the CV in on the Volca
• On the Volca front end, a patch cable runs from the CV in GATE to the AR/ENVELOPE GATE input
• On the Volca front end, a patch cable runs from the CV in PITCH to the SOURCE PITCH input
• An oscilloscope is hooked to the headphones output of the Volca
• From the Beatstep, I play one "continuous C" pattern for each octave and scribble the measured frequency my notepad
• I use this chart as a standard to compare with measured values in my test
C2/0V / 67 / 65.4 / +40.87%
C3/1V / 133 / 130.8 / +28.2%
C4/2V / 267 / 261.6 / +34.5%
C5/3V / 556 / 523.3 / +105.2%
C6/4V / 1137 / 1046.5 / +145.4%
C7/5V / 2439 / 2093 / +278%
C8/6V / 4082 / 4186 / -44.3%
The pitch signal, when taken from the CV pitch patch port on the Volca face, is also not very steady, it wobbles a little (and it shows when hearing the note being played). This definitely comes from the Volca, because when I measure the voltages coming from the Beatstep at the end of the cable (on the TRS connector), the values are nice and steady.
Also, pitch from the internal sequencer of the Volca is spot on. So it's got to do with the CV in signal processing, apparently.
Any idea what's going on here? I can describe the setup more if needed.
