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Electro-Harmonix Holy Grail

Digital Reverb Processor By Paul White
Published August 2002

The Electro-Harmonix Holy Grail is probably the simplest digital reverb unit on the planet. Designed for guitar, the pedal will work with any instrument-level source, including -10dBu line signals. It has a high input impedance to suit electric guitars, but only a single, unbalanced mono output. By way of controls, there's a three-way slide switch and a wet/dry mix knob, plus a bypass footswitch. Power comes from an included 9V adaptor.

Electro-harmonix Holy Grail reverb pedal.Three reverb options are available via the slide switch: Spring, Hall and Flerb. The first, Spring, is modelled on the spring reverbs found in typical guitar combos, right down to the rhythmic flutter, though there's no 'sproing' when you kick the unit! As with the real thing, the only variable is how much you dial in, but I thought it was actually pretty good. Next is 'Hall', and though it may be a little on the generous side for some types of music, it's absolutely perfect for doing cover versions of Peter Green's 'Albatross' or that type of blues that sounds as though it was recorded at a large venue when nobody turned up! As for Flerb, the manual (actually a piece of blue paper) says that it is 'a beautiful reverb like nothing you have heard before and may help you to play your instrument in new ways'. To me, though, it sounds like a flanged reverb, a bit like the guitar effect on the intro to 'Shine On' by Pink Floyd, though the modulation was preset a little too deep for my taste.

Of course, the weakness of any pedal reverb is that you're not actually adding reverb at the best place in the signal chain, unless you're playing clean guitar. Ideally it should come after the preamp (where most of the distortion happens in a modern guitar amp) so that clean reverb can be added to the distorted sound. Placed at the front of the signal chain, anything more than mild overdrive will mess up the reverb, so the main beneficiaries are clean players or those who get their distortion from a pedal before the reverb unit. The quality is good though, other than a hint of background hiss which, after all, is an Electro-Harmonix tradition. Even so, I'm not sure the title Holy Grail can be honestly applied, though Damned Fine Coffee Mug wouldn't be stretching things too far.


  • No learning curve at all!
  • Two more reverbs than most guitar amps provide.


  • A little noisy.
  • Mono output limits usefulness in recording.


A no-frills digital reverb in stomp-box format.


£104.76 including VAT.$136.

Electro-Harmonix +1 718 937 8300.