The Electro-Harmonix Holy Grail is a compact digital reverb pedal with three modes selected by a toggle: Spring, Hall and Flerb. Vintage Guitar reviewed it in June 2002 as "their new digital Holy Grail Reverb pedal," made in the U.S.1 It grew out of a prototype completed around 2002, and the family later expanded into the Holy Grail Nano, Holy Grail Plus, Holy Grail Neo and Holy Grail Max.
Its appeal is simplicity. As JHS Pedals' Nick Loux put it in a buying guide, "It literally has one knob that says reverb, and when you turn it up, it adds more reverb."2 MusicRadar's reviewer wrote that "the Holy Grail's single control takes it from the ambience of a small room to a huge concert hall."3
What it does: spring, hall and flerb
The pedal has three modes, spring, hall and flerb3. Spring is the sound most players associate with the Holy Grail: Electro-Harmonix calls the Nano version's Spring mode "simply the finest 'spring' reverb available"4, and on the JHS Pedals history video Josh said, "I think in the spring setting, this thing is unbeatable," calling it "the first ever to my knowledge digital spring reverb unit"5.
Flerb is the odd one. Electro-Harmonix describes it as combining "flanging with spatial reverb for a unique ethereal sound"4. Guitar Interactive's press release glossed it as "reverb+flanging"6. Not everyone loves it: JHS Pedals wrote of the Holy Grail, "I love the Holy Grail reverb, it's legendary, but the Flerb setting is a monstrosity"7, and the company built its 3 Series Pherb pedal around fixing it7. Josh also recounted that Flerb was chosen over a room mode deliberately: "Mike Matthews, I have the note. Weird electroharmonics. Flurb. Because it's weird."5
When it appeared, the pedal had little competition. Josh noted that around 2002 "the only thing that existed in this realm was uh RV3 boss RV3 Digitech had the Digi Verb"5.
The controls
The original is about as simple as a pedal gets:
| Control | What it does |
|---|---|
| Reverb knob | One knob; turn it up for more reverb2 |
| Three-way toggle | Selects Spring, Hall or Flerb3 |
| Footswitch | Engages and disengages the effect (Nano version)4 |
The toggle was only three positions because Electro-Harmonix wanted to mimic the Small Clone, Small Stone format of its classic pedals5. The knob acts as a wet/dry control on the Nano version4.
History: from prototype to Nano and Neo
Development started in 2000, when Mike Matthews saw the Crystal CS4811 chipset, pre-programmed with reverb algorithms, at a trade show8. The prototype was wrapped around 20025, designed by John Pasani with help from Dave Vaneps and Ross Tatino5. Pasani marked the prototype in Sharpie: "Holy grail one, handle with care"5.
In January 2026, JHS Pedals' Josh Scott and Daniel Danger found that prototype while digging in the basement at Electro-Harmonix in Queens8. The story of the find, and the book that came out of it, was covered by Guitar World8.
The line then grew:
| Version | Released | Modes | Notes |
|---|---|---|---|
| Holy Grail | 2002 | Spring, Hall, Flerb | Original, buffered bypass31 |
| Holy Grail Plus | 2008 | Spring, Hall, Room, Flerb | Discontinued 20229 |
| Holy Grail Nano | 2009 | Spring, Hall, Flerb | Compact chassis, true bypass, power adapter included4 |
| Holy Grail Neo | 2015 | Spring, Hall, Plate | Update to the compact Holy Grail, true bypass1011 |
| Holy Grail Max | 2014 | Spring, Hall, Plate, Reverse | Blend and Time controls, true bypass1213 |
The Plus added a Room mode plus a Blend knob controlling the wet/dry mix from 100% dry to 100% wet, and a multifunction control for decay, damping and modulation speed9. The Max, announced in January 2014 with a U.S. list price of $214.1214, carries Spring, Hall, Plate and Reverse with a Blend control and a Time control that sets decay time, or reverse time in Reverse mode13. The Neo, announced in March 2015 at a U.S. list price of $163.3711, "dispenses with Flerb in favour of a more useful plate sound," as Guitar.com's guide put it15.
The Holy Grail Plus was discontinued in 2022, per Electro-Harmonix's product page9. The newer versions of the Holy Grail do not use the Crystal chip because it is out of production5.
Eight hidden sounds in the Rev A units
The original production units shipped with three reverb sounds on the outside, but inside there was more. As Josh explained on the JHS Pedals video58:
"they had the three sounds on the outside and then inside, if you knew it, and some people figured it out, you could hack it and you had eight total sounds."5
The prototype itself exposed this directly: "what you do have are these dip switches. And so these dip switches are eight different reverb sounds"5. Guitar World reported the same of the Rev A production units: "some people figured out that you could hack it and have eight total sounds via the dip-switches"8. The hack only works on Rev A units with the Crystal CS4811 chipset; later versions dropped the chip because it is out of production5. On the prototype, the mode toggle does not work5.
The JHS Pedals video covers the prototype's history and demos its sounds:
Who uses it
Players who have documented the Holy Grail in their rigs include Ryan, who on the JHS video described gigging with one hard: he used to put Holy Grail reverbs in the back of a Fender Bassman cab and leave them on all the time, gaff taping the knobs and switch5. The pedal's history also connects it to the people who built it: on the same video, Josh recalled that a prototype was found while digging in the basement at Electro-Harmonix in Queens, and that the circuit was designed by John Pasani, with help from Dave Vaneps and Ross Tatino5.
Videos
ProGuitarShopDemos
EHX
EHX
Questions
What is the flerb setting on the Holy Grail?
Flerb is the Holy Grail's third mode, alongside Spring and Hall. Electro-Harmonix describes it as combining flanging with spatial reverb for a unique ethereal sound. On the JHS Pedals video about the pedal's history, Josh noted that Flerb was chosen over a more conventional room mode simply because Electro-Harmonix wanted something weird.
Is the Holy Grail true bypass?
The original Holy Grail is buffered, not true bypass, according to MusicRadar's 2021 reverb pedal roundup. The later versions are true bypass: Electro-Harmonix lists the Holy Grail Nano, Plus and Max as true bypass, and RockBoard's PedalPedia lists the Neo as true bypass as well.
What is the difference between the Holy Grail Nano and Neo?
The Nano (2009) keeps the original's Spring, Hall and Flerb modes in a compact chassis. The Neo (2015) is an update that drops Flerb and carries Spring, Hall and Plate algorithms instead. Both are mono digital reverbs with a single wet/dry reverb knob and a three-way mode selector, and both ship with a power adapter.
How do you unlock the hidden modes on a Holy Grail?
On the Rev A production units built around the Crystal CS4811 chipset, the original three sounds can be expanded to eight by hacking the internal dip switches, which select eight different reverb sounds. This only works on units with the Crystal chip; later versions do not use it because the chip is out of production.
Why is it called the Holy Grail?
Mike Matthews, Electro-Harmonix's founder, named the pedal. According to the JHS Pedals video on the pedal's history, he was a big movie buff at the time and named it after Indiana Jones, whose third film is Indiana Jones and the Last Crusade, the quest for the Holy Grail.
Is the Holy Grail Plus discontinued?
Yes. Electro-Harmonix's product page marks the Holy Grail Plus, released in 2008, as discontinued in 2022. It added a Room mode, a Blend knob for the wet/dry mix and a multifunction control for decay, damping and modulation speed on top of the original's Spring, Hall and Flerb reverbs.
Sources (15)
- Electro-Harmonix Holy Grail, Vintage Guitar magazine, 2003-04-01
- SIMPLE PEDALS FOR EVERYONE!, JHS Pedals
- 5 great reverb pedals guitar players need to try, MusicRadar (www.musicradar.com), 2021-10-12
- Holy Grail Nano, Electro-Harmonix
- I Found The Prototype! (Where The Electro-Harmonix Holy Grail Reverb All Started), JHS Pedals (YouTube), 2026-01-26
- Electro-Harmonix Expands Reverb Line with Holy Grail Neo, Guitar Interactive Magazine, 2015-03-18
- 3 SERIES PHERB, JHS Pedals, 2026-10
- Lost EHX Holy Grail prototype found, Guitar World, 2026-01-31
- Holy Grail Plus, Electro-Harmonix (ehx.com)
- Holy Grail Neo, Electro-Harmonix (ehx.com)
- Electro-Harmonix Unveils the Holy Grail Neo, Guitar.com, 2015-03-26
- Holy Grail Max, Electro-Harmonix
- Demo Video: Electro-Harmonix Introduces Holy Grail Max Reverb Pedal, Guitar World, 2014-02-25
- New EHX Pedals: tortion, Holy Grail Max & Satisfaction, Premier Guitar, 2014-01-22
- All About… Reverb, Guitar.com, 2015-08-06
Lee Kiernan
Madi Diaz
