The Walrus Audio Fathom Multi-function Reverb is a reverb pedal with four algorithms: Hall, Plate, Lo-fi and Sonar. Walrus Audio describes it as "a feature-rich reverb with 4 different customized reverb algorithms to choose from." It is no longer made: the maker's product page states plainly that the pedal "is discontinued and no longer available"1. When it was announced in January 2018, Walrus Audio offered it at a retail price of $1992.
The four algorithms
Each mode is a different reverb character, and the X knob changes its job depending on which one is selected1:
| Algorithm | What it does | X knob |
|---|---|---|
| Hall | Wide, open and vast, with decay that ends in high-frequency rolloff | Not specified |
| Plate | Full body reverb with a smooth decay | Adjusts pre-delay |
| Lo-fi | Filtered reverb, decay ranging from warm to a thin AM-radio sound | Adjusts filter width |
| Sonar | Reverb fed with both a high and a low octave | Blends the octaves |
The Sonar mode is the Fathom's octave reverb. Guitar Interactive's Jonathan Graham described it as "a blendable shimmer/octave" and "a tip of the hat to its older brother, the Descent," Walrus Audio's earlier octave-oriented pedal2.
Controls and how they work
Beyond the mode selection, the Fathom gives a player three ways to shape the sound. RockBoard's PedalPedia notes that the dampen knob is used "to fine tune the tone of the reverb's decay," and that the toggle switch "adds options for low, medium and high modulation"31. RockBoard sums up the range as letting a player "easily go from tasteful, small room reverb to long, modulated trails dripping of ambient goodness"3.
The pedal has two footswitches, a Bypass Switch and a Sustain Switch, both with momentary functions. When the pedal is off, pressing and holding the Bypass Switch temporarily activates the effect to add a moment of reverb, and releasing it turns the effect off again1.
Power and practical notes
The Fathom runs on 9VDC at a minimum of 100mA1, and RockBoard's listing gives the current draw as 100mA3. Walrus Audio recommends an isolated power supply for all of its pedals1.
The Fathom is discontinued and no longer available from Walrus Audio1. It has buffered bypass rather than true bypass1, and RockBoard's PedalPedia lists the circuit type as analog3.
Design and finish
The pedal comes in an Arizona Teal finish with cream and white ink, with original artwork by illustrator Stuart Dooley showing a lone one-manned sub lost in the chasmic depths, searching for the origins of the mysterious Julia, a reference that ties it visually to Walrus Audio's Slö1. The diecast enclosure measures 4.77" x 2.6" x 1.39"1.
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Questions
What does the X knob do on the Walrus Fathom?
The X knob does a different job in each algorithm. In Plate mode it adjusts pre-delay, in Lo-fi mode it adjusts filter width, and in Sonar mode it blends the high and low octaves that feed the reverb. Guitar Interactive's Jonathan Graham described it as changing pre-delay, filter width or the low and high octave mix, respectively, for each algorithm.
Does the Fathom have a shimmer or octave reverb?
Yes. The Sonar algorithm is a reverb fed with both a high and a low octave, and the X knob blends between them. Guitar Interactive described Sonar as a blendable shimmer/octave and a nod to Walrus Audio's earlier Descent pedal.
Is the Walrus Audio Fathom analog or digital?
RockBoard's PedalPedia lists the Fathom's circuit type as analog. It runs on 9VDC at a minimum of 100mA, so it needs its own isolated power supply rather than a daisy chain.
Does the Fathom have buffered or true bypass?
The Fathom has buffered bypass, according to Walrus Audio's product page.
What is the momentary function on the Fathom?
When the pedal is off, pressing and holding the Bypass Switch temporarily activates the effect, and releasing the switch turns it off again. The pedal has two footswitches, a Bypass Switch and a Sustain Switch, both with momentary functions.
Is the Walrus Fathom discontinued?
Yes. Walrus Audio's product page states the Fathom is discontinued and no longer available. It was offered at a retail price of $199 when it was announced in January 2018.
Sources (3)
- Fathom Multi-Function Reverb, Walrus Audio
- Walrus Audio Fathom Multi-Function Reverb, Guitar Interactive Magazine, 2018-01-16
- Fathom Multi-function Reverb by Walrus Audio, RockBoard (PedalPedia), 2026
