Welcome to the strange new world. The R-54 is the most radical, revolutionary module we've ever made. It will change the way you do music synthesis. There has never been an electronic-music product like this before. Even the oddest things that Buchla And Associates or Serge Modular ever made are prosaic and dull compared to the R-54.
It uses a triode-pentode in a unique Wien-bridge circuit, to provide clean sine-wave oscillation. Using a Vactrol, the pitch of the R-54 is sweepable from less than 20 Hz to more than 5 kHz, continuously, via front-panel control or a CV input. By adjusting the waveshape/resonance control, the sinewave signal produced by the R-54 can be trimmed to less than 10% THD (depending on operating pitch)---with NONE of the problems inherent in solid-state oscillators and sine waveshapers. Because the Wien bridge contains no piecewise sine shaper or amplitude-control circuit or component. The tube itself performs that job. So the distortion products are entirely low-order, unlike the "sine waves" that solid-state VCOs or samplers produce.
Turn up the overdrive control, and the oscillator output clips the output amplifier pentode tube, for a unique soft-clipped square-wave sound. The simplicity of the R-54 will fool you--its behavior is odd and radical, and it will take you months or years to fully explore all of its quirks.
Now for the special trick. Plug an audio signal into the audio input. Instantly, the R-54 transforms from a VCO into a bandpass resonant voltage-controlled filter, with the same range as in VCO operation -- 20 Hz to 5 kHz. Its behavior and sound are unique. Again, you will be kept busy for years exploring all of its strangeness.
And now, it's got two new tricks. A VCA CV input allows you to control the output level of the R-54 as well as the amount of clipping in the output tube. Plus, a HARSH switch introduces a feedback loop into the CV control. Turn up the output level and the R-54 does very strange things.
CV response: Hz/v. Use a suitable MIDI/CV interface, or use our R-60 interface to obtain perfect equal-tempered tuning every time. Maximum output signal, 12 v p-p. Power requirement: +-12v dc, approx 150 mA. (All specifications are approximate and may vary from sample to sample.) Tubes used: 19KG8, 6AK5.
The Metasonix R-series of vacuum-tube modules is intended for use in any "Eurorack" standard modular synthesizer system. All R-series modules are 22HP (112mm) wide and fit in any Doepfer(tm), Analogue Systems(tm), or other compatible cabinet. They are powered entirely from the cabinet's internal +-12v dc power supplies, using Doepfer compatible 16-pin power connectors. Their circuits protrude behind the panel less than 25mm (1 inch). All vacuum tubes are NOS (new old stock) types from classic American and European manufacturers that are run very conservatively for long life, and are readily available from distributors. The tubes protrude from the panel for visibility and cooling, less than 38mm (1.5 inches), and should fit inside a Doepfer A-100 suitcase cabinet lid or into a Doepfer mini case. All audio inputs and outputs and CV inputs/outputs are 100% compatible with other synthesizer modules. Plate voltage is provided by a tiny switching supply producing clean 48v regulated at low current, which is very safe and will not injure the user. Potentiometers are top-quality Alpha RK12L types, and 3.5mm phone jacks are special Kobiconn vertical-mount types, much better quality than the cheap ones usually seen in Euro modules. Each R-module is fully protected against reverse supply voltage, overvoltage, undervoltage, or incorrect hookup to external equipment. As with all our products, the R series is totally handcrafted in Northern California, USA.