Sunday, January 09, 2011

A-178 Theremin Control Voltage Source

The Theremin, invented in the late 1920's by Léon Theremin was one of the earliest electronic instruments.
The instrument is known for it's distinctive ( spooky ) sound, but most of all for it's playing method; Instead of playing it with a keyboard, the Theremin has antennas that sense the movement of the players hand, without touching the instrument.
Best known for playing the Theremin is Clara Rockmore, one of Theremins finest students.

Most theremins use two antennas, usually one for pitch and one for volume, so with two Doepfer A-178 Theremin Voltage Source modules, an oscillator (VCO) and an amplifier (VCA) module, it is quite easy to re-create the sound of a 'real' Theremin. You can even easily extend that sound by patching in filters or other modules.

And again, that is what makes the A-100 modular so versatile. 
Instead of just recreating the original Theremin you can use the module as a control voltage source for other modules. 

The voltages can be used for controlling any voltage controlled parameter of the A-100, e.g. pitch or pulsewidth (VCO A-110/111), loudness (VCA A-130/131/132), panning (A-134), filter frequency or resonance from all of the filter modules, phasing (A-125), frequency shift (A-126), resonance peaks (A-127), envelope parameters (A-141/142), and tempo (A-147), to name just a few ;-)

The Gate-output with adjustable threshold (not available on the original Theremin) is a nice extra output. I often use this for (re-) triggering notes or filter effects, but it can also be used for starting sequences (A-155) or for reset or switching functions (A-152).

Doepfer recommends if two or more A-178 are used the distance between the modules/antennas should be at least 30 cm to avoid interference.


  1. Very interesting. How difficult is it to play this module though? I've always understood that the original theremin is very difficult in that respect.

    Marc JX8P

  2. @Marc Good question. Playing the instrument takes practice, as most instruments do. The antennas are very sensitive so little movement can have large effects. For controlling volume or filtering the voltage doesn't have to be too precise though.
    For pitch control this is different; together with the Theremin module i always use an A-156 Quantizer Module, just to make sure i hit the right (whole) notes (or other scales that the A-156 provides). That, together with atouch of the A-170 Slew Limiter to add a 'glide' effect will make playing the Theremin a lot easier and sounds quite natural. It's the same trick i use for playing the A-198 Ribbon Controller.

  3. I've been thinking about these too Pierre, It looks like a great way of playing and adding expression. I like the ribbon controller too (I have the R2M version which has an in-built quantizer). I have just taken delivery of the Analogue Systems RS-35 which has a pitch to voltage function - I will use it with my guitar (when I actually get some free time that is!).