The TM-1 is a tube-based signal-processing device hand-made in California and housed in a heavy, yellow, Hammond-style case. It has five comfortable knobs and five jacks and runs on an AC power adapter. I wanted to open it up to check out the interior construction, but there's a warning sticker across the seam telling me not to do this. (Perhaps the 60 V plate voltage inside might fry a lawyer or two.) The TM-1 sports a bright LED pilot light and a stomp switch that I was surprised to see was made of plastic. This is the only remotely cheesy-feeling thing about this sturdy box. Inside are three NOS tubes, which you can make out by peering through the little porthole on the control panel.

Metasonix recommends sending a robust signal through the TM-1, such as a synthesizer or preamped guitar. I did try some guitar, but got the most interesting results out of my synths. The TM-1 worked fine with a Yamaha CS01, and things really got cooking when I plugged in my SCI Pro-One, which has a very hot output.

The first section on this pedal is the preamp, which is controlled by a single knob. It does not offer clean, transparent gain. Even with everything else turned down, it colors the signal significantly and interestingly, offering a nice, fuzzy distortion. (This was less true with the CS01 and its quieter output. Oddly, the preamp actually attenuated the Pro-One's signal; the bypassed audio was always louder than the TM-1's output, regardless of which controls were engaged.) Next, the signal passes through the pulser, a tube which deforms the waveform, and the beam switcher, a tube which to my ear seems to add strange harmonics. The manual also says it's responsible for the ring modulation, which is the last thing your audio has to endure; here, the TM-1 generates a solid-state carrier signal which interacts with the oscillation of the beam switcher. This ring mod is pretty odd-extremely thick and blurry around the edges. A great sound, in my opinion.

The controls are interactive, especially the pulser stability and beam tube screen knobs. You can use these to bring your sound right to the edge of chaos and beyond, introducing all manner of humming, spitting, and squealing. The most exciting sounds this thing makes come right on that edge, just before everything seems about to flop over into wild self-oscillation.

The ring mod, unfortunately, has no gate, so when it's on, it's just on, droning away in the background. If you're just using the audio in and out, this limits its use. Its two controls are for tuning the pitch and dialing in the amount of effect. I did enjoy tuning it to a particular note-C for instance-then playing around in that key, returning to the tonic with a barrage of thick, detuned oscillation. But the sound is way out of control and never shuts off. This feature makes me think that the place this unit really belongs is in a modular synth setup-after the oscillator and before the filter and amplitude envelope. And indeed, you can buy a rackmount kit for several different modular systems.

There are three other jacks: CV inputs for the beam switcher and VCA, and an audio input for the ring mod carrier. These offer an additional amount of control which you'll want to experiment with if you have a modular system. I patched the Pro-One's CV output into everything for the hell of it, and even stuck the CS01's audio in all the jacks as well. The results were pleasingly strange and unpredictable. This circuit tracks audio signals in a semi-intuitive way, but it's kind of like teaching a cat to fetch. If you have a preconceived idea of what your result should be, you'll probably be disappointed.

Overall, this is an esoteric piece of equipment that sounds genuinely unique. The closest thing I've heard is the Sherman Filterbank, though the TM-1 has a meatier, thicker sound overall, if less control. If you want something to plug your guitar into on stage and stomp with abandon, this may not be your cup of tea-and the bypass switch won't thank you, either. But if you have a sophisticated setup that will allow you to tweak this device and explore its inputs and outputs, you'll find something to use it for. It's weird, cool, and could kill you if you open it. What's not to like? ($439 MSRP;

Tape Op is a bi-monthly magazine devoted to the art of record making.

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