R-56 Vacuum-Tube Reverb - 28HP

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Item: N13-2266

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R-56 Vacuum-Tube Reverb - 28HP


The R-56 is unique and never before available in any form. It is a limited-issue product.

It uses two 9-pin miniature triode-pentodes, type 12CT8. The design is optimized for maximum sound quality and minimum noise and hum. It is presently the only vacuum-tube spring reverb usable in a Euro-rack modular synthesizer.

The Input Drive level allows adjustment to suit any signal level, from -10dBu to the hottest module audio output. By overdriving the input, tube distortion is added, then solid-state distortion effects, from subtle to extreme. The two Output Level controls allow adjustment of the output mix, between totally "dry" (no reverb effect) to totally "wet" (reverb effect signal only). An added "Wet Only" output jack carries only the Wet signal for experimentation.

A feedback loop allows for direct feedback around the spring. This effect is independent of the input signal and affects any input signal. It can produce feedback oscillations whose frequency is dependent on the spring delay time and the driving signal. An Invert switch allows inversion of the drive signal to the spring input, which can produce drastically different sounds, especially on bass-heavy transients such as bass drums.

The miniature reverb spring "tank" is mounted directly on the front panel. If physical access to the springs is desired, the plastic cover can be easily removed by undoing two snaps.

Two CV inputs are available. One for controlling input preamp gain, from complete cutoff (-2v) to maximum drive to the spring. The other controls the feedback loop around the spring, for a wide range of chaotic distortion effects (the Feedback control knob must be turned up for this effect to operate, as it uses a vactrol to increase feedback around the potentiometer).

If the users wishes to attach a larger (guitar amp style) spring tank assembly, a set of RCA jacks on the rear is provided. The external tank should have an input impedance of 300 ohms or more, and an output impedance of 1000 ohms or more. The internal and external tanks may be operated together in parallel, for very complex reverberation effects.

Because the R-56 is a special limited-issue module, it uses an extremely high-quality custom engraved anodized aluminum front panel, with black paint infill.


  • Audio Input
  • Drive CV In
  • Feedback CV In
  • Mix Output
  • Wet-Only Output
  • Input Level Control
  • Feedback Control
  • Wet Level Control
  • Dry Level Control
  • Drive Signal Invert Switch

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  • Eurorack Module
  • 28 HP Width
  • 1.5' Depth
  • Vacuum Tubes are NOS types from classic American & European manufacturers
  • +12v: 300mA Current Draw
  • -12v: 300 mA Current Draw
  • 800-850 mA cold startup is required for 3-5 seconds

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