Dual Mini Synthesizer Operating Instructions

Connections

CV IN: Accepts a 1 volt/octave control voltage to control the pitch of the oscillator.  It responds from about 0-5V, but voltages outside of this range won’t cause damage.  The CV input is quantized, so only valid (western scale) notes are played.  This input is ignored when Sample & Hold is enabled.

GATE IN: A voltage greater than about 2.5V will turn on the gate and allow audio to come out the output of the synth.  

VCO SHAPE IN: Adjusts the wave shape of the main oscillator. Responds to 0-5V. A plug in this jack disables the corresponding pot.

GLIDE IN: Adjusts glide time. Responds to 0-5V. A plug in this jack disables the corresponding pot.

LFO1 SHAPE IN: Adjusts the wave shape of LFO1. Responds to 0-5V. A plug in this jack disables the corresponding pot.

LFO1 RATE IN: Adjusts the rate of LFO1. Responds to 0-5V. A plug in this jack disables the corresponding pot.

VCO SHAPE IN: Adjusts the wave shape of the main oscillator. Responds to 0-5V. A plug in this jack disables the corresponding pot.

LFO->VCO: Adjusts which LFO(s) modulate the pitch of the main oscillator and how much (see below for further details). Responds to 0-5V (~2.5V should give you no modulation, the same as if the pot for this control were in the 12:00 position). A plug in this jack disables the corresponding pot.

LFO->VCA: Adjusts which LFO(s) modulate the amplitude of the main oscillator and how much (see below for further details). Responds to 0-5V (~2.5V should give you no modulation, the same as if the pot for this control were in the 12:00 position). A plug in this jack disables the corresponding pot.

LFO2 SHAPE IN: Adjusts the wave shape of LFO2. Responds to 0-5V. A plug in this jack disables the corresponding pot.

LFO2 RATE IN: Adjusts the rate of LFO2. Responds to 0-5V. A plug in this jack disables the corresponding pot.

Attack IN: Adjusts attack time. Responds to 0-5V. A plug in this jack disables the corresponding pot.

Release IN: Adjusts release time. Responds to 0-5V. A plug in this jack disables the corresponding pot.

AUDIO OUT: Connect to an amplifier or another module.

Controls

S&H Button: Enables Sample & Hold, which disables the external CV IN jack and uses LFO1 and LFO2 to determine oscillator pitch.  LFO1 sets the sample rate (SHAPE is ignored for this), and LFO2 is the wave that gets sampled.

GATE Button: Manually turns on the gate so sound comes out of the synth.  This control is momentary, but you can latch it on by tapping the S&H button while holding the GATE button down.

COARSE TUNE: Adjusts the pitch of the oscillator up or down in large increments

FINE TUNE: Adjusts the pitch of the oscillator up or down in fine increments

SHAPE: Changes the shape of the wave produced by the main oscillator (VCO).  Turning this control fully CW gives you a triangle wave.  Start turning it CCW takes you through sawtooth/ramp, then at about the 12:00 position you get a square wave.  Continue turning it CCW and you get several higher duty cycle square waves.

GLIDE: Adjusts the rate at which the pitch of the VCO takes to go between pitches (whether changed by the COARSE TUNE knob or CV IN).  Fully CCW causes the pitch to react almost instantly, while fully CW makes it take its sweet time.

LFO 1 / LFO 2 SHAPE: Changes the shape of the waves produced by the low-frequency oscillators (LFOs).  The shapes are similar to those of the VCO, except that the LFOs have sawtooth/ramp waves that go both up and down (since you can actually hear the difference at LFO rates).

LFO 1 / LFO 2 RATE: Controls how fast the LFOs go.

LFO -> VCO: Routes the two LFOs to control the pitch of the main oscillator.  The 12:00 position is basically “off”, and the LFOs have no effect on pitch.  Start turning the control CCW and LFO1 starts changing the pitch of the VCO.  Maximum effect is at about 10:00.  Continuing to turn the control starts to bring in LFO2 as well.  All the way CCW gives you full effect from both LFO1 and LFO2. 

Turning the control CW from 12:00 does essentially the same thing, but brings in LFO2 first, then LFO1.

This might seem like kind of a weird control, but it gives you quite a bit of routing flexibility with one knob.  You can have no pitch modulation, LFO1, LFO2, LFO1 with a little LFO2, or LFO2 with a little LFO1.

LFO -> VCA: Routes the two LFOs to control the amplitude of the oscillator.  (See LFO -> VCO control description above for more information about how the control works.)

ATTACK: Controls how fast the audio amplitude fades in when the gate is triggered.  CCW is fast and CW is slow.

DECAY: Controls how fast the audio amplitude fades out when the gate is released.  CCW is fast and CW is slow.

FILTER: Changes the cutoff frequency of an analog low-pass filter.  Turn the knob fully CW and all frequencies (that you can hear) are let through.  Start turning it CCW and the high frequencies start getting cut off, until the sound becomes muddy / muffled.  Use in conjunction with the SHAPE control to get the tonal quality you are looking for.

Calibration

Here’s a way you can calibrate the CV input of your synths to match the voltages generated by your exact hardware (needs to be done for each synth 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

Restore Default Note Map

If the calibration gets too far off or you mess it up, you can reload 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

 

Dual Mini Synthesizer Documentation
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