Limited Edition TX-2 "Butt Probe" from Metasonix

June 17, 2005

The Metasonix TX-2 is entirely made of vacuum tubes. To be specific, three type 4BN6 beam modulator devices. They were intended for use in crummy TV sets as FM detectors, and were NOT meant for audio processing applications. Its distortion sounds can be strange and extreme.

The TX-2 can accept guitar, mic or line-level signals, though it works best with line level. By utilizing the inherent non-linearity of the 4BN6 tubes, the TX-2 offers a broad range of distortion effects. Carefully adjusting the FIST and REAM controls allows the user to vary the screen-grid voltages of the first two tubes--FIST controls the first (input) tube, REAM the second tube in the string.

This changes each tube's gain and distortion behavior in a very drastic fashion. It can be adjusted from a mild tube-ish warmth, to horrid screaming broken-amp ultra-distortion.

Instability is inherent in a circuit having this much gain, and the third tube provides an extra way of modulating the distortion. Basically, it is wired as a very bad bandpass filter. Filter center frequency is controlled with a "Vactrol" type optical resistor, and swept continuously with a low-frequency oscillator built into the TX-2. The sweep may be disabled by turning down the SCREW knob or by plugging an unassigned 1/4" plug into the CV IN jack. If the latter is done, the SCREW knob will tune the filter manually, giving a vast range of tonal effects not obtainable with any of the existing effect pedals on the market.

Each TX-2 Butt Probe is hand-made and hand-painted in Northern California. Because they're hand-painted, they all vary in appearance, and may include smearings of brown paint and scribbling of epithets on them.

As an extra special "feature", the Butt Probe's front panel has offensive cartoons by comic artist Sarah Combs, and its owner manual contains EXTREMELY offensive cartoons by "Retarded Animal Babies" creator Dave Lovelace. Dave's cartoons are so disgusting, we will NOT make them available anywhere else. (He outdid himself.)


  • Power consumption: 12 volts AC only at 1.0 amps
  • Size: 8x4.5x2.5 inches, weight approx 4 pounds
  • Inputs: one mono audio, one control voltage (sweeps filter), both 1/4" TS. Output: STEREO audio, 1/4" TRS
  • Output is usually >20 dB hotter than input. Not recommended for use with guitar amp input, suggest line level input
For more information, visit their web site at

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