This Eurorack module houses two complete synthesizer voices. They’re based on the Business Card Synthesizer with all its 8-bit goodness, but adds CV inputs for most of the controls.
Features (each synth)
- Pulse, square, triangle, and sawtooth waves
- 2 LFOs with pulse, square, saw, triangle and ramp shapes
- Attack / Decay
- Low-pass filter
- Sample and Hold
- Manual gate trigger (can be locked on)
- Course and fine-tune controls
- Power supply: +12VDC (reverse-polarity protected!).
- Width: 18HP
- Depth: 0.83in / 21mm
Notes not stable on some control voltages
Sometimes the control voltage being received by the synth is right on the edge between what it considers to be two different notes, and there’s enough noise in the signal that it switches back and forth between the two notes. Here’s a way you can calibrate the CV input of your synth to your exact hardware (you’ll need to do this for each synthesizer in the module):
- Connect your voltage source (like the Dual Mini Sequencer) to the synth (both CV and Gate)
- Make sure everything has been turned on for a while so the temperature has a chance to stabilize
- Turn the Coarse Tune knob all the way counterclockwise
- Go to the lowest octave on the sequencer and press the lowest (C) note. The sequencer should be sending out ~0V
- Hold down the S/H button on the synth. After a couple seconds, the S/H LED will start to flash. You are now in calibration mode
- Start playing notes on the sequencer, starting from the bottom C, and work your way up (C, C#, D, D#, E…). Go through all the notes in all the octaves. Hold each note for half a second or so. You should hear them stabilize and not wiggle
- Once you’ve programmed all the notes, release the S/H button. The synth will exit calibration mode, the new note map will be saved to non-volatile memory, and you should be able to use the sequencer to play the synth without any wiggly notes.
Notes (the informational kind, not the musical kind):
- If the calibration was too far off to begin with, you may need to run through this procedure a couple of times
- When calibrating, the synth assumes the first note you send it will be a C, but it will detect which octave you are working with, so you don’t always have to start with 0V. For example, if you only want to calibrate the upper octaves, you could start with 3V and the calibration routine will know that you have skipped the 0V, 1V, and 2V octaves.
- During calibration, every time the synth receives a gate, it samples the voltage at the CV input and sets that to be the center voltage for the next note (starting with C of the nearest octave)
- You can calibrate the synth to other sequencers and CV sources too. You just need a way to send it a gate to let it know when it’s time to sample the voltage for the next note.
- If the calibration gets too messed up you can re-load the default note map. Hold the S/H button when powering on the synth. After the version number is displayed on the LFO LEDs, the S/H LED will flash 3 times to let you know that it’s been reset.