The METASONIX TM-3 is the only voltage-controlled oscillator on the market with an all-tube signal path. It consists of two thyratron tube sawtooth oscillators, which are wired in parallel but may be offset with their individual front-panel tuning controls. Furthermore, soft sync is available, to force oscillator 2 to track with oscillator 1.

Extended information

The waveform produced by the 2D21/5727 thyratrons is unique and distinctive--a very imperfect sawtooth. It's the kind of sound that screams "VINTAGE", because the only other instruments that produce it are vintage ones--the Mixtur-Trautonium, the Univox, and some 1950s electronic organs.

Furthermore, there is a suboctave circuit, which adds a square wave one octave below oscillator 2. It includes short pulses an octave above, for a distinctive sound. And you can mess with the STABILITY control to get unique effects--because the suboctave divider is made of two neon lamps, and NOT a transistor flip-flop. Except for the CV driver, the TM-3 is all tubes.

And unlike most other synthesizer VCOs, the TM-3 is so sensitive that it is easily used for FM sound effects--simply by driving either CV input with a line-level audio signal. Both inputs are DC coupled and highly sensitive. The result is a unique, and very extreme, form of signal distortion.

The TM-3 is a Hz/V VCO, meaning it follows a linear characteristic. Each successive octave requires doubling the control voltage. As shipped, the first octave is swept from 0 volts to 0.25 volts, the next from 0.25 to 0.75 volts, etc. Although not standard to the present modular-synth industry, this scheme simplifies the TM-3's use as a signal processor, and avoids the use of an exponential converter circuit, which can drift with temperature or cause other problems. TM-3's CV control is compatible with vintage Korg MS series and Yamaha CS series synthesizers.

Technical specifications

Output signal max approx 10 v p-p. Capable of approximately three octave range with CV control, 66 Hz to 526 Hz. Center pitch setting with tuning knobs and 0.0v input gives approx. low C (66 Hz). Actual range obtained depends upon individual thyratron tubes installed--about 2 1/2 octaves is typical. May be controlled from any MIDI-CV converter having Hz/V capability, including the Synhouse MIDIJACK II, Philip Rees Little MCV, Kenton Pro-Solo and Pro-2000, and Encore Expressionist.
The TM-3 is optionally available with a Synhouse MIDIJACK II MIDI-CV converter built in. This does not affect any of the other functions of the TM-3; the MIDIJACK operates from the TM-3's power supply. A MIDI input plug is installed on the front of the TM-3. This is an extra-cost option, available, only upon original order of a TM-3. Contact Metasonix for pricing and more information.
Power input 10v AC to 12v AC, 50/60 Hz, 1 amp max at idle--derived from an appropriate plug-in AC adapter. Inputs: two 1/4" phone jacks for CV or audio (they mix linearly). Output: 1/4" phone jack, audio, mono, 50k ohm impedance.
All Metasonix TM series modules may be used as standalone effects boxes. Or they may be mounted in 5U-high standard modular synthesizers (MOTM, Synthesizers.com, Moog) using our TM-M kit. Or, they may be mounted in Eurorack-based modular synthesizers (Doepfer, Analogue Systems, Analogue Solutions) using our TM-D kit. Our modules are the only ones in the WORLD capable of this.
Dimensions: 7 1/2" (192mm) x 4 3/8" (112mm) x 3" (77mm). Weight not including accessories approx. 5 pounds (2.2 kg).