Boss FRV-1 '63 Fender Reverb is a discontinued compact guitar pedal that digitally recreates the sound of a vintage tube-driven 1963 Fender spring reverb unit using COSM (Composite Object Sound Modeling) technology.

The form factor is the Boss pedal norm, and the controls are those of the original — Mixer, Tone and Dwell.  The FRV-1's knobs accurately emulate the actions of the originals, and the resulting reverb is a very close approximation of the Fender's warm, all-encompassing, twangy tonality, and its range, which can go from the subtlest of background jazz shimmers to the total wet madness of full‑on surf, via all points in between and beyond.

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I’m not a guitar player but tested this effects device with recorded music in and out to audio amplifier.  With a 9V battery installed, all controls work and the sound is altered as expected.

In very good cosmetic condition.  The previous owner fastened Velcro pads to the bottom.