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Theremax Controls

old image (Pitch and Volume Trim control locations are reversed)


  • Pitch & Volume Trim – these control provide a vernier null of the reference and variable heterodyneing oscillators in the Pitch and Volume control circuitry.
  • Pitch CV – controls the range of control voltage produced in response to hand proximity to the vertical pitch antenna on the right side of the instrument.  Clockwise rotation increases range up to a maximum of 6 Volts.  This control does not effect the sensitivity of the internal pitch circuitry.
  • Timbre – controls the brightness of the internal tone generator. At full counter-clockwise rotation the output is pure sine wave.  At full clockwise rotation the output is a square wave.  Intermediate settings produce a mix of the two.
  • Velocity – controls sensitivity to rate of change of volume level.  At min, there will be no velocity response no matter how fast volume is changed.  Rotation toward max produces increasing response.  At max, the Velocity Control Voltage output will produce a 4 Volt change in response to the quickest possible hand gestures.  This CV is a transient with a time constant on the order of a second.  Internally, this CV biases the VCA for asymmetrical distortion, with no distortion at the min setting (asymmetrical, transient distortions are responsible for some of the perceived “punch” in natural instrument).  This control also sets Gate/Trigger sensitivity, at max sensitivity the gate will respond to very slow movements of the Volume hand.
  • Volume – adjusts the sensitivity of both the internal VCA and external Volume CV output to hand movement relative to the Volume antenna.  Output level is adjusted here, but more importantly this control is capable of driving the VCA into symmetrical distortion (symmetrical distortions are responsible for much of the “loudness” of instrument when played fortissimo).


  • Mute – a foot switch, or S-trigger to this jack mutes the internal pitch producing circuitry.  CVs are not effected.
  • Pitch CV – Control Voltage proportional to hand proximity to the Pitch antenna as ranged by Pitch CV control.
  • Volume CV – Control Voltage proportional to hand proximity to the Volume antenna as ranged by Volume CV control.
  • Velo. CV – Control Voltage proportional to how fast a hand is moved in proximity to the Volume antenna as ranged by Pitch CV control.
  • Gate/Trigger – This TRS jack provides a 5 V. gate signal at the “tip” when Velocity exceeds a threshold.  The “ring” connection is an S-Trigger compatible closure to ground.  The LED lights to indicate a triggered condition (note that the gate responds to change in volume, i.e. how quickly the volume control hand is moved, not the static location of the hand).
  • Audio Out – Output level is adjustable with the volume control but is nominally -10 dB.
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