METASONIX TS-21 Hellfire Modulator

Redefining the word "distortion."Sometimes the simplest devices yield the richest results. Such is the case with the TS-21 Hellfire Modulator, which Metasonix

Redefining the word "distortion."

Sometimes the simplest devices yield the richest results. Such is the case with the TS-21 Hellfire Modulator, which Metasonix touts as "the world's most aggressive and complex distortion generator." The TS-21 is the first in the company's line of tube-based synth modules.

Metasonix has put its knowledge of tube circuitry to good use in the design of the TS-21. The unit is made up of three stages, each with its own tube: a preamp with a VCA, a pulse-width modulator (PWM), and an LFO-controlled waveshaper. Vacuum tubes are also used for the LFO and for powering additional circuits, giving you a total of five tubes in the device. Despite the tube count, however, the TS-21 has very low self-noise and gets only slightly warm to the touch.

Because of the type and configuration of the TS-21's five tubes, Metasonix states that the Hellfire Modulator works best with edgy signals, such as square and sawtooth waves from synthesizers. In fact, the company says that the device was created primarily for use with analog modular synthesizers. I accepted the challenge and mated the unit with my Buchla, Moog, Oberheim, and Technosaurus gear. In addition, I ran other sound sources through the TS-21, including electric guitar, theremin, drum loops, and a variety of samples.

GO WITH THE FLOWThe TS-21 is housed in a rugged 2U box that has the look and feel of military surplus gear. The front panel's symmetrical layout makes it easy to visualize the signal path through the unit. Because the I/O jacks are on the front panel, interfacing the unit with your modular-synth gear is a straightforward matter.

In the center of the front panel is a darkened, circular window through which you can view the dimly glowing tubes inside. To the left of the window is an unbalanced 11/44-inch TS audio input, a 11/44-inch CV input to the VCA, controls for input level and pulse-width shape (PWM/Manual), and switches marked PWM/Bypass and Range. On the right are the Beam Screen, L1, L2, and Speed knobs; a 11/44-inch jack for the Beam/PWM CV input; and a 11/44-inch TRS stereo jack for audio output. What I found handy is that both CV inputs gladly accept the output of an LFO and envelope generator, as well as control voltages.

From the input, the signal flows first to a pentode tube preamp, then through a PWM tube, and finally through a waveshaper circuit, allowing you to shape the sound at each of these stages. The CV VCA input affects only the input signal (though Metasonix will wire the VCA to the output by request); its effectiveness is controlled by the position of the PWM knob. Having a VCA at the input stage seemed a little strange to me at first, but I quickly discovered the potential of this configuration. For instance, modifying the loudness contour of the source material before it goes to the next stage in the system is very useful if you're looking for radical sound modification.

The next stage is the PWM circuit. When the PWM/Bypass switch is in the PWM position, the PWM/Manual knob controls the switch point of the circuit by changing the width of the pulses. The PWM circuit uses positive feedback, and you can easily set it into self-oscillation by turning the PWM knob past 9 o'clock.

The Range switch adds further unpredictability to the processing by sending the signal to different electrodes on the beam tube. However, the sonic results are dependent on the other front-panel settings. For example, sometimes the Range switch has no audible effect; at other times it pushes the signal to a new level of distortion. Occasionally it will cause the output level to drop a bit, although you can correct this by adjusting the L1 and L2 controls.

ON THE BEAMThe unit's Beam Screen knob controls the beam-modulator stage. Metasonix claims that the balanced modulator tube in this stage (6AR8/ME8/JH8) was intended to be a chroma detector in television sets, and that it has never been used in audio equipment before. When you hear how it treats an audio signal, you will understand why Metasonix chose to use it in the TS-21.

As the Beam Screen knob passes the 12 o'clock position, the gain increases, causing the waveform to fold over on itself in unpredictable ways. Turning the knob clockwise as far as possible results in a hum, which further intensifies the output with some source material (particularly harmonic-rich synth signals). On source material (such as samples and loops), it merely sounds annoying.

At this point in the signal path, you can process your source material in ways that render it unrecognizable. But the fun doesn't stop here.

THE JOY OF PANNINGTo go the extra distance, Metasonix wired an LFO to the beam modulator. In conjunction with the L1 and L2 knobs, the LFO controls how the beam switches between two anodes of the tube. The result is a panning effect when you use a TRS insert plug in the output jack.

The positions of L1 and L2 determine how evenly the panning occurs, while Speed controls the panning rate. You can set the TS-21 to pan in strange, limping rhythms that are unique to this device. Such rhythms can sometimes make the panning effect seem unstable, but in a musically interesting way. Additionally, the sound sent to each channel is noticeably different both in sound quality and volume, yet both channels share elements of the source material.

Finally, the Beam/PWM CV input affects the settings of both the Beam Screen and PWM/Manual controls. Again, you can use an LFO or high-gain audio signal to drive it.

The only unwanted noise I detected from the TS-21 was a quiet ticking from both outputs when the input was turned completely off. Metasonix says this is a result of the LFO. Newer TS-21 models have a switch that lets you turn the LFO (and the ticking sound) off.

GENTLE MANIPULATIONSTo get the most out of this device, you must take care in setting the controls, because the slightest adjustment can have a profound effect on the sound. Make a large move with one of the knobs, and you may pass over something amazing.

Occasionally, after working on a particular sound for a time, I found that the PWM was in self-oscillation and the source signal was no longer present at the output: the device itself had become the unintended source instrument. This is not necessarily a bad thing. The fact that the TS-21 can be used as an oscillator (in more ways than one) is another interesting feature.

ONE OF A KINDMetasonix intended for the TS-21 to be used with modular synthesizers. However, I found myself treating the device itself as a voltage-controlled synth module. After I'd spent just a few moments with the TS-21, it seemed to take on a life of its own. Hours later, I gained an awareness and appreciation of its many subtleties.

Considering that the TS-21 is a single-channel processor, the biggest drawback for some will be its $749 list price. However, the TS-21 is unique in that it uses tubes to do the processing. The resulting sound quality speaks for itself, and serious synthesists and sound designers will appreciate this aspect of the unit. If the words grainy, saturated, and mangled appeal to you, or if you thought there were only a few ways to distort a sound, you're in for a treat with the TS-21.