There is a joke buried in the name, and Walrus Audio tells it themselves on the product page: “Calling someone Slö in Swedish may be considered an insult to some, but with adjectives like sleepy, drowsy and lazy, this perfectly describes the ambient atmospheres and tones the Slö can create.” It is a small thing, but it tells you everything about the design brief. This is not a pedal built to give you a convincing plate on a snare-adjacent rhythm part. It is a pedal built to make your guitar sound half-asleep, and it is very good at it.
Released in April 2019 into a market that was already drowning in ambient reverb — Strymon had owned the high end for years, EarthQuaker had the weird end locked down, and every builder in Oklahoma, Ohio and Ontario had a shimmer box in development — the Slö did something unusual. It refused to be a do-everything reverb. Three algorithms. One toggle. Five knobs. Two footswitches. No presets, no MIDI, no stereo. And it went on to become one of the most photographed pedals on the ambient, shoegaze and post-rock circuit, boarded by MONO, Bully, Nothing But Thieves, Dance Gavin Dance, Walk the Moon and Soccer Mommy, and still in Walrus Audio’s Core Series seven years later.
It is also, and we are going to be straight about this early, a pedal with a genuine and well-documented flaw. The noise floor is real, and Walrus have reportedly attributed it to the chip inside. That flaw is a large part of why the Slöer exists — and none of it has dented the Slö’s reputation.
Where the Slö Came From
The Slö did not arrive out of nowhere. It is the third entry in a lineage that Walrus Audio had been building since the mid-2010s, and Premier Guitar’s Joe Gore put it plainly in his review: “In recent years, Walrus Audio has released several pedals based on a common theme: pitch-shifted digital reverb. In that regard, Slö is a successor to Walrus’s Descent Reverb/Octave Machine and Fathom Multi-Function Reverb.”
The Descent was the big, ambitious one — a reverb and octave machine with a footprint to match. The Fathom was the compact, practical one. The Slö ignored the workhorse brief entirely and went for texture. One long-time owner laid out the family tree better than any press release: “from the Descent to the Fathom to the newer Slo, Walrus delivers in a way that makes me feel a little cold towards other manufacturers. The Fathom can be used for some fairly basic sounds and makes a great workhorse in that sense, but the Slo dives right into the deep end, and all the better for it.”
That is the entire pitch. The Fathom is the reverb you buy to have a reverb. The Slö is the reverb you buy because you want a specific kind of dream.
The Launch: April 2019
The release date is unusually easy to pin down. Effects Database’s chronological video index shows the classic embargo-day cluster: on 15 April 2019, roughly twenty demo videos landed at once — Walrus Audio’s own trailer, Pedal Play film and Tech Demo, plus Rabea Massaad, 60 Cycle Hum, Gearmanndude, Mike Hermans, Chords of Orion, EytschPi42 and others, followed the next day by Sweetwater, Chicago Music Exchange and Reverb’s Tone Report. That is a coordinated launch, and it dates the pedal precisely. Launch price was $199 street — £192 in the UK, €199 in Europe.
What’s Actually Inside: The Spin FV-1
The single most important technical fact about the Slö is one that most retail listings never mention: it runs on a Spin Semiconductor FV-1 DSP chip. Joe Gore confirmed it in Premier Guitar in September 2019 — “Slö’s sonic palette is wide and varied, thanks to its use of the multi-faceted Spin FV-1 chip” — and Premier Guitar restated it three years later when reviewing the Slötvå, describing it as derived from “the company’s very similar Spin FV-1 chip-based Slö reverb.”
The FV-1 is the workhorse behind an enormous number of boutique digital pedals, and it is the reason a small builder in Oklahoma City can ship a three-algorithm modulated reverb for two hundred dollars instead of six hundred. It is also, depending on your ears, the reason some people never warm to the Slö at all. Gore was blunt: “The FV-1 doesn’t generate hi-fi digital reverb effects. (Spin reverb often sounds grainy and shallow to me, but apparently many guitarists disagree. They’re certainly buying tons of Spin-based stompboxes!)”
He then immediately made the case for the defence, which is the more useful half of the observation: “the Spin tones can be quite workable when heard through a signal chain with multiple distortion stages and amp/speaker coloration — especially when accompanied by bass, drums, or other instruments.” That is the correct frame for the Slö. Auditioned alone, clean, on headphones, the grain is audible. Auditioned where it actually lives — behind a fuzz, in front of a driven amp, in a band — the grain reads as character.
Gore also noted something that matters more than it sounds: “the chip is surprisingly good at interpreting chords as well as single notes.” A lot of octave-fed reverbs fall apart on anything more complex than a dyad. The Slö holds triads together even at fully wet settings, which is precisely why it works for the pad-and-drone crowd.
The Three Algorithms
The toggle picks one of three programs, and — this is the bit that trips up new owners — the X knob does a completely different job in each. Walrus’s own documentation is unusually clear on this, so we will follow it.
Dark (Lower Octave)
Walrus: “Add a lower octave to your reverb trail. Here you’ll create deep and wide atmospheric sounds and channel nightmarish soundscapes. X knob sets the level of a -1 octave signal that feeds the reverb.”
Note the wording: the octave feeds the reverb, not the dry signal. Your fundamental stays where it is; the tail grows a basement. MusicRadar’s Trevor Curwen mapped the range — with X at minimum and Decay low you have “a pretty standard reverb for everyday use,” and as you open X up you get “a unison guitar/bass sound with ambience,” then something “weighty and doom-laden” at the top. Dark is the mode people buy the pedal for. One owner’s entire published settings note reads, in full: “DARK MODE BOI.” Not a sophisticated critical judgement, but an accurate one.
Rise (Ambient Swell)
Walrus: “This is an auto-swell reverb for beautiful cinematic swells. Don’t rush it. Let it breathe and gently wake up. X knob sets the amount of time it takes the reverb to swell in after a note is played. Set lower for shorter rise times and higher for longer rise times.”
Joe Gore made the most useful comparison anyone has made about this mode: Rise “delays note attack in the manner of the old Boss SG-1 Slow Gear pedal before routing it through reverb.” The Slow Gear is a cult vintage unit that trades for silly money, and Rise gets a large slice of its behaviour as a side effect. The catch: Rise only swells the wet path. Your pick attack is still there in the dry signal, so a true volume-swell needs Mix pushed well past halfway.
Dream (Latching Pad)
Walrus: “Here is a lush reverb with a latching pad function. Press the sustain switch to latch signal. Experiment with the X knob to add vibrato over the pad. Press sustain again and pad will decrescendo according to where decay knob is set. X knob sets the depth of vibrato applied to the reverb trail.”
This is the party trick, and Curwen explained the workflow perfectly: “you can play, say, a G chord, hit the footswitch and get a reverb pad in the key of G to play over until you hit the footswitch again to let it fade out naturally (with trails on).” It is a freeze function that sounds like a reverb rather than a sampler — softer-edged and more musical than a hard freeze, and considerably easier to live with than a looper for one-person ambient work.
One owner buying direct from Walrus put it best in December 2024: “using the latch to create a beautiful floating pad and then playing over it. Pure joy and honestly 20 minutes with this is better then any meditation app I have tried.” He was running it on an acoustic board, after modulation and before a basic reverb/delay combo — a placement worth stealing.
The Hidden Layer: Wave Shapes, Momentary Functions and Trails
Three Modulation Wave Shapes
Hold the bypass switch down and move the algorithm toggle, and you are no longer selecting reverbs — you are selecting the modulation shape applied to the tail. Walrus’s definitions:
- Sine — “Smooth and even pitch up and down modulation.”
- Warp — “Asymmetric pitch up modulation similar to a warped record.”
- Sink — “Asymmetric pitch down modulation for sinking detune similar to a Bigsby.”
Curwen’s note on how they behave in practice: “The sine wave is the most conventional and can offer chorus and rotary speaker-style effects, while the others each have their individual detuned take on things.” Sine is the one that gets you close to running a chorus after your reverb; Warp and Sink are the ones that make the tail sound like it is on damaged tape. If you already run a Walrus Audio Julia V2 or a Julianna in front of it, dial the Slö’s own modulation back — the two stack into mush surprisingly quickly.
The wave shape and rate are stored per algorithm, which is a nice touch: your Dream setting can carry heavy Sink while your Dark setting stays clean.
The Two Footswitches
Depth normally sets modulation intensity; hold bypass and it becomes modulation rate. This is the one feature MusicRadar flagged as a negative — its only listed con was “Some might find setting the secondary function is a bit of a faff” — and it is fair. You are holding a switch with your foot while turning a knob with your hand, listening for a change you cannot see.
The bypass switch is also momentary. Gore singled it out: “When pressed and held, the bypass switch momentarily activates the reverb. That’s great for adding a touch of reverb only to selected passages.” On a pedal with no presets, that is how you get a “reverb on this one phrase” gesture without stomping twice.
The Sustain switch is the real differentiator. In Dark and Rise, holding it “ramps up the reverb trail to maximum creating long dreamy reverb trail and then ramps back down to the decay knob setting when released.” In Dream it latches instead. MusicRadar called it “the inspired addition of the Sustain footswitch,” which “adds a leftfield twist that offers cool performance options” — the feature that separates the Slö from every set-and-forget reverb at this price.
Trails
Trails and no-trails are toggled the old-fashioned way: hold down the bypass switch for one second while applying power, then unplug and repeat to switch back. In trails mode the tail decays naturally when you disengage; in no-trails it is cut dead. There is no front-panel indication of which mode you are in, so if you buy used, assume nothing and set it yourself.
Specifications
One spec deserves a flag because the aggregators get it wrong. Equipboard’s product table lists the Slö’s bypass as “True Bypass: Yes” and its power draw as 80 mA. Walrus Audio’s own specification block says, in three words, “Buffered Bypass,” and specifies 100 mA minimum. The manufacturer is right and the aggregator is wrong, and it matters: buffered bypass is exactly why the pedal can do trails at all. A true-bypass pedal physically cannot let a tail ring out after you disengage it.
Famous Players: What Actually Holds Up
Before the roster, the correction — because the source list we were handed for this article named The Edge, John Mayer, Mark Lettieri and Mateus Asato, plus a vague gesture at “ambient guitarists.” Exactly one of those four survives contact with the evidence.
The Edge has run rack-based delay and reverb since the early 1980s and has never been documented with a Slö. John Mayer has no documented Slö usage of any kind. Mark Lettieri is the interesting one, because he is a genuine Walrus user — he posted a board photograph featuring the Walrus Julia in November 2019 — but a Julia is a chorus, not a reverb. That looks very much like the source of the error: a real Walrus connection attached to the wrong Walrus box. Only Mateus Asato holds up.
Tier One: On the Record, In Their Own Words
Takaakira “Taka” Goto (MONO) is the best-evidenced Slö user in existence, and the only one who has published settings. In an August 2025 interview with Guitar Magazine Web, walking through his live pedalboard, Goto confirmed the Slö and specified that he maxes out both the Decay and the Filter knobs on the MONO songs “Run On” and “We All Shine On.” Filter fully open plus Decay fully open on a Slö is a very specific sound — bright, enormous, endless — and it is not the setting most owners default to. It is worth trying purely because a working post-rock guitarist chose it deliberately for two named songs. Equipboard additionally credits the pedal on MONO’s 2024 album OATH, which is chronologically clean.
Mateus Asato filmed his own pedalboard walkthrough and, at 12:04, talks through his signal chain: the Walrus ARP-87, the Julia chorus and the Slö reverb, all three from the same builder. Self-filmed, self-narrated, unambiguous. Our Mateus Asato gear guide has the wider rig.
Tier Two: Photographed and Filmed
Hideki “Yoda” Suematsu, Goto’s counterpart in MONO, has been documented with the Slö since 2020 in both live and studio contexts, including an Instagram post captioned “OATH RECORDING.” Two Slös in one band is about as strong a genre endorsement as post-rock can offer.
Alicia Bognanno (Bully) can be seen with the pedal on her board five seconds into a WFUV session video — a live-to-camera radio performance, which is a useful class of evidence because nobody dresses a board for radio.
Joe Langridge-Brown (Nothing But Thieves) had the Slö on his board in a photograph Nothing But Thieves posted on 22 May 2026, in preparation for BBC Radio 1’s Big Weekend. That is the most recent independent sighting available and it is on an arena-scale rig.
Soccer Mommy was photographed with one at KEXP on 3 November 2021. Will Swan (Dance Gavin Dance) posted a picture of new pedals bought in Toronto with the Slö among them — a useful reminder that this is not exclusively an ambient player’s pedal; Swan’s band is aggressive, technical post-hardcore. Doyle Martin of shoegaze band Nothing, Eli Maiman (Walk the Moon) — pictured in an April 2019 post, within days of launch — and NARASAKI of Japanese shoegaze-metal outfit Coaltar of the Deepers round out the photographed users.
The Thin One, and the Impossible One
Two entries do not survive scrutiny, and it is worth saying so.
Pat McCrory (Turnstile) appears on the roster on the strength of a caption reading, in its entirety, “In this photo the outline and layout of a Slö can be seen.” An outline — not a legible graphic, not a visible logo. McCrory is a documented Walrus user elsewhere, so it is plausible. It is not evidence.
Anna Calvi is a straightforward impossibility. The credit rests on a Substack post detailing the gear from her 2018 Hunter tour, and the same source lists Hunter (2018) as an album the Slö appears on. The Slö did not exist in 2018 — it shipped in April 2019. The album credit is simply wrong: the same failure mode we caught on the Julia, a database back-propagating a current pedalboard onto an older record.
The Siblings’ Rosters, For Completeness
The Slötvå has two credited users, neither strong: Yvette Young (Covet) in a launch-window demo dated 11 January 2022, captioned “Going through presets with the new Walrus Audio Slötva!” — launch-partner content rather than independent rig evidence — and Juan Cordero, identified from a YouTube Short by artwork alone.
The Slöer does better. Dave Harrington (Darkside) confirms it in a Premier Guitar Rig Rundown, and it is credited on Darkside’s 2025 album Nothing. Tim Pierce, the Los Angeles session giant, shows the Slöer in a rig video at around 6:15 with an honest caveat built into his own description — he uses it for “just one song.” Our Tim Pierce gear guide covers the rest of that board. Jake Beitel (Prize Horse) rounds out the credible entries; a fourth is sourced to a private Facebook profile, which no reader can check.
The Reference Points the Slö Is Chasing
None of the following players use a Slö. All of them are the sound the Slö is reaching for, and it is more useful to say so than to pretend otherwise. One long-standing owner review nailed the target list: “If you’re a fan of super ambient/textured bands like Sigur Rós, Slowdive, Daughter, This Will Destroy You, Explosions In The Sky, etc. this pedal is for you! It’s literally ‘post rock in a box.'”
Neil Halstead of Slowdive and Robin Guthrie of Cocteau Twins built the vocabulary the Slö speaks, years before anyone put an FV-1 in a 125B. Kevin Shields got there via tremolo-arm detune, and Sink mode is the closest a Slö gets to that queasiness. Vini Reilly and Bill Frisell are worth studying if you want Dream’s latching pad to sound musical rather than decorative, and Thurston Moore and Lee Ranaldo are why Dark mode sits so naturally under detuned, open-string playing.
Tone Recipes
MONO / Post-Rock Crescendo (Goto’s Published Setting)
Dark. Decay max. Filter max. Mix 1 o’clock. X 10 o’clock. Depth 9 o’clock, Sine. Straight from Goto’s Guitar Magazine interview: both Decay and Filter pinned. Filter wide open keeps the tail bright enough to sit above a distorted rhythm bed rather than under it, which is the opposite of the usual instinct with a dark reverb. Keep X low so the octave adds mass without turning it into a drone.
The Meditation Pad
Dream. Decay 3 o’clock. Filter 11 o’clock. Mix 12 o’clock. X 10 o’clock. Depth 10 o’clock, Sine. Play a triad, latch it with Sustain, then play over the top. X adds vibrato to the held pad only — a little goes a long way, and past 1 o’clock it starts to sound seasick rather than serene. Unlatch and the pad decrescendos at whatever Decay is set to, so use Decay as your fade-out length.
Slow Gear Impression
Rise. Decay 11 o’clock. Filter 1 o’clock. Mix 4 o’clock. X 2 o’clock. Depth off. Gore’s Boss SG-1 observation, made practical. Mix needs to be well past halfway or your unswollen pick attack gives the game away. X at 2 o’clock is a long enough rise to feel deliberate without losing the note. Add a compressor such as the Xotic SP Compressor in front to even out the swell envelope.
Doom / Drone Bed
Dark. Decay max. Filter 9 o’clock. Mix 3 o’clock. X max. Depth 1 o’clock, Sink. The “nightmarish soundscapes” Walrus’s own copy promises. Full octave, filter clamped down, Sink modulation dragging the tail flat. Hold Sustain and it becomes a wall. Works startlingly well after a big-box fuzz — an EarthQuaker Hizumitas or a Big Muff Pi — provided the fuzz is before the reverb.
Twelve-String Thickener
Dark. Decay 10 o’clock. Filter 2 o’clock. Mix 10 o’clock. X 9 o’clock. Depth 11 o’clock, Warp. Small amounts of everything: the octave-down at a whisper thickens the fundamental rather than announcing itself, while Warp’s asymmetric pitch-up does the chorusing. The setting most likely to survive into an actual song.
Ambient Loop Foundation
Dream. Decay 2 o’clock. Filter 12 o’clock. Mix fully wet. X 12 o’clock. Depth 12 o’clock, Sine. Fully wet is unusually usable here — Gore noted “Even 100 percent wet settings can yield useable tones.” Capture a latched pad, then play dry over it. Stack a EHX Freeze and it turns orchestral.
Subtle Verb for Actual Songs
Dark. Decay 9 o’clock. Filter 1 o’clock. Mix 9 o’clock. X fully down. Depth off. Curwen’s observation that “if you keep that at minimum and the Decay low then you have a pretty standard reverb for everyday use” is true, and worth knowing if you only have one reverb slot. It is not the Slö’s reason for existing, and a Boss RV-6 does this job better and quieter. But it exists.
Bass and Synth
Dark. Decay 1 o’clock. Filter 10 o’clock. Mix 10 o’clock. X 11 o’clock. Depth 9 o’clock, Sine. Plenty of owners run the Slö on bass and synths — one keyboardist called it “capable of sustain and reverse effects and it has a really ‘noir’ dark-mode” (wrong about the reverse; that is the Walrus Lore). Keep Mix low so the fundamental stays defined, and use Filter to keep the tail off the note.
All settings assume clock positions with the knob at 12 o’clock as centre. Mix has a marked 50/50 point at roughly two o’clock, which MusicRadar correctly noted gives you “more travel to play with when dialling in the lighter mixes” — most of the useful subtle territory lives between 9 and 1.
Where the Slö Goes in the Chain
The default answer is last, after everything, and for most players that is right. But the most useful placement advice on this pedal came from an owner who put it before dirt: “For the ones that already possess a reverb pedal, this pedal would make a lot of sense to place before your dirt, that way there is little to no overlap between the two and you’d unlock a lot of shoegaze and post-rock/metal tones.” That is a real technique. Reverb into fuzz smears the tail into the distortion rather than putting distortion into a room, and it is a large part of how shoegaze guitar actually sounds.
Community data on what the Slö actually shares boards with is not what you would guess for an ambient pedal. The most common companions are a Boss TU-3, a Pro Co RAT 2, a Boss BD-2, a Strymon El Capistan, a Keeley ECCOS, the Walrus ARP-87, a Keeley Compressor Plus, a Big Muff Pi, EarthQuaker Plumes and a Boss GE-7. That is a rock board with an ambient reverb bolted on, not an ambient rig — which matches the verified player roster far better than the pedal’s reputation does.
Two practical notes. Put a good tuner in front — a PolyTune 3 Mini or the TU-3 — because muting through a trails-mode reverb is otherwise a nuisance. And if you stack the Slö with a delay, run the delay first: Carbon Copy or Dispatch Master into the Slö gives distinct repeats blooming into a wash, while the reverse turns to porridge fast.
Slö vs Slötvå vs Slöer
Slötvå (2022)
Same three algorithms, same FV-1 platform, same enclosure, plus three saveable presets. That is the entire difference, and it directly answers the most common Slö complaint: one owner’s review is literally headlined “Would buy again, but with presets,” and reads “I’m as close as I can be to loving this pedal if only it had presets.”
Premier Guitar’s Charles Saufley reviewed it in August 2022 at $229 street, scoring 4.4, with pros “Intuitive. Great range in all controls. Well-built” and one con: “Some digital artifacts at long decay times.” His warning applies equally to the Slö: “the octave content can reveal chorale-style overtones and discernibly digital artifacts at long decay times. Some players love and utilize these sounds to great effect. So, try before you buy if you don’t know where you stand.”
The Slötvå appears to be out of production — catalogue data lists it as 2021–2023, and it is missing from most major retailers — but it is still findable new around $129.99 at Guitar Center and zZounds, which is less than a new Slö. If you can find one at that price, it is the better buy: the Slö plus presets for less money.
Slöer (2023)
The full redesign. Stereo in and out, five algorithms (adding Rain, a diffused delay-tap reverb, and Light, an octave-up shimmer), five wave shapes (adding Square and Random), three presets, a Stretch control that adjusts the sample rate, and sliders instead of knobs for X and Stretch. Street price $297.49 against a $349.99 list.
The honest verdict from testers who own both: “frankly if you don’t have a stereo rig, you can get most of the Slöer’s mojo with a Slö or Slötvå.” The size is real, too — “nearly 5 inches wide, which is almost the width of two standard size pedals.” But there is one reason to spend the extra, and it is the noise floor.
The Noise Question
This is the part of the Slö story that most coverage skips, and it should not be skipped.
The top-voted owner review on the pedal’s largest community page is titled “Great ambient reverb with a hugely disappointing flaw,” and it says this: “As much as I love this pedal, it has a deal breaking flaw. Regardless of whether you set it as buffered or true bypass, the pedal will add background noise, and a lot of it. I go to great lengths to make my board as quiet as possible so this was an instant dealbreaker. Walrus says this is due to the internal chip used (FV-1) so this has nothing to do with amp, cable or pickups used.”
That same owner later bought a Slöer and reported back: “After returning a Slö due to how noisy of a pedal it is, I’m glad to report that the Slöer solves all of the noise issues that the Slö had in any of the bypass modes.” Reddit-sourced owner commentary says the same of the Slötvå — “Users report noise issues with the Slötvå, even when using isolated power.” Same reviewer, three pedals, one conclusion: the FV-1-based Slö and Slötvå have a noticeable noise floor and the Slöer does not. If you play at bedroom volume with a lot of gain, or record direct, this is your deciding factor, and it is worth the extra $110 to skip straight to the Slöer.
If you play in a band, through an amp, at volume, you will most likely never hear it. Note that the same product page carries 4.6 out of 5 across 44 ratings, and Walrus’s own store shows 4.9 from 62 reviews with 98% five-star. The noise is real and it is a minority complaint. Both things are true.
What the Reviews Actually Said
Premier Guitar (Joe Gore, 15 September 2019, October 2019 issue, $199 street). Pros: “Fresh-sounding ambient tones. Player-friendly interface. Excellent build quality.” Cons: “Mono only. The Spin FV-1 reverb sound can be a matter of taste.” Verdict: “The reverb quality, while not stellar to my ears, is par for the price range. If you relate to its spacy/dreamy textures, Slö more than merits a place on your pedalboard.” Gore’s design note is the best one-line explanation of the layout: “Slö strikes a canny compromise by using five knobs and one toggle. The top knob row controls the basic reverb settings. The second row modulates them.”
MusicRadar / Guitarist (Trevor Curwen, 28 June 2019, £192 / €199 / $199). Pros: “Compact size. Three different ambient reverbs. Footswitch to hold the reverb.” Con: “Some might find setting the secondary function is a bit of a faff.” Verdict: “Ideal for players who want the option of deep ambience in their signal chain without using up a massive chunk of ‘board space.” His framing of where the pedal sits is the sharpest summary anyone has written: “The Slö falls between these two extremes, its vibe being one of cherry picking some of the most interesting ‘altered’ reverbs you might find in one of those larger units and putting them into a practical, streamlined working format.” Walrus also picked up an Editor’s Choice nod from Guitar Magazine for the pedal.
How It Compares
vs Strymon BigSky
The obvious upgrade, and the community’s note on it is refreshingly honest: “It’s got a lot of options too but holy crap do you pay for it…” The BigSky has twelve algorithms, stereo, presets, MIDI and a noise floor the Slö cannot match, at roughly twice the money. What it lacks is Dark mode’s octave-fed character and the Dream latch as a single-press gesture. The Slö is not simply a cheap BigSky.
vs EarthQuaker Devices Afterneath
The closest philosophical rival, and the one Slö owners name most often. The Afterneath is a delay-tap diffusion machine — cavernous, granular, scattered — where the Slö is smooth and pitched. One owner who has both: “My favorite reverb. I also love the Afterneath but the Slö is just so beautiful.” The Slöer’s Rain mode is essentially Walrus’s answer to the Afterneath.
vs Boss RV-6 and RV-500
The Boss RV-6 is the cheaper, quieter, more sensible option and it does the shimmer and the spring the Slö cannot. The RV-500 is the deep-menu flagship. Neither has a latching pad footswitch and neither sounds remotely like Dark mode. Buy a Boss to have a reverb; buy a Slö to have a texture.
vs EHX Oceans 11 and Holy Grail Neo
Oceans 11 is the value champion — eleven algorithms, including a shimmer and a polyphonic mode, for well under half the Slö’s price. The Holy Grail Neo is the one-knob workhorse. The Slö’s advantage over both is footswitch performance control; if you never intend to hold a switch mid-song, the EHX pedals are the rational purchase.
vs Keeley Caverns, TC Hall of Fame 2, OBNE Dark Star and Meris Mercury7
The Keeley Caverns gives you a delay in the same box; the TC Hall of Fame 2 has TonePrint and MASH and is the most conventionally versatile of the bunch. Neither makes the noise the Slö makes in Dark mode. Against the OBNE Dark Star, owners describe the Slö as more “heavy-handed,” where the Dark Star “offers a stealthier sound that blends well with other effects”; against the Meris Mercury7, some players simply prefer the Meris for ambient work. Both are fair. The Slö is not a subtle pedal, and pretending otherwise sets buyers up for disappointment.
Buying Guide, September 2026
New
List is $219.99 and street is $186.99 — the same number direct from Walrus Audio, Sweetwater, Guitar Center and Musician’s Friend, all of which currently flag it as a $33 all-time low. Reverb has it at $186.01 with over 40 units in stock new. Thomann lists $199, Gear4Music £182, zZounds holds at full list $219.99. Market average across all channels sits at $187.
Crucially, the Slö is still in production — present in the Core Series > Delay and Reverb navigation on Walrus Audio’s own site, and absent from the Discontinued collection. Seven and a half unbroken years in a boutique core line, through two successor models, is itself a verdict.
Used
Used excellent examples start around $149.99. Against $186.99 street, that is roughly 80% value retention on a seven-year-old digital pedal — stronger than the ARP-87’s 72%, and level with the Julia and Julianna. Unlike the ARP-87, the Slö has no workflow quirk that makes owners bail within a year; people who resell one almost always do so because they bought a Slöer.
The circuit has never changed, so there is no reason to prefer a newer unit. Check three things: that both footswitches respond to momentary holds as well as clicks, that trails mode toggles with the power-up trick, and — the one real complaint — the noise floor at a realistic gain setting.
B-Stock and Limited Editions
Walrus runs a permanent B-Stock collection, and it remains the single best value play on any pedal they make. One buyer’s review is representative: “I purchased it as B-stock, but I couldn’t find any blemishes. It’s definitely worth the price!” The standard Slö appears there regularly.
Limited editions exist across the range — Platinum, Obsidian, Gold Standard, National Park and Kamakura runs, plus Black Friday variants. All the same circuit. Buy the graphic you like; do not pay a premium expecting a sonic difference.
Living With It
Power it from an isolated supply at 100 mA or better. Walrus explicitly discourages daisy chains, and on a pedal with a known noise floor that advice is not boilerplate. There is no battery compartment, so there is no fallback.
Learn the two secondary functions before you gig it — hold-bypass-plus-toggle for wave shape, hold-bypass-plus-Depth for modulation rate. There is no cheat sheet on the enclosure, and the manual (seven languages, free from Walrus’s site) is worth reading. Set trails mode deliberately, too: trails on is right for almost everyone, but it means the pedal’s buffer is always in your signal path.
And be honest with yourself about presets. The Slö has none and it is the single most common owner regret. If you switch textures between songs, or need a specific Dream setting recallable in a dark room with three seconds’ notice, you want the Slötvå or the Slöer. If you play one long ambient set and adjust as you go, the Slö’s immediacy is the feature.
Frequently Asked Questions
Is the Walrus Audio Slö true bypass?
No. Walrus Audio’s own specification says buffered bypass, switchable between trails and no-trails. Several third-party listings state “true bypass,” and they are wrong — trails mode requires the signal to keep passing through the circuit after you disengage, which a true-bypass switch physically cannot do.
Is the Slö noisy?
It has a measurable noise floor attributed to the Spin FV-1 chip, and it is the one consistent owner complaint. At gig volume in a band, most players never notice; at bedroom volume, recording direct, or with a lot of gain in front, some find it a dealbreaker. The Slöer resolves it.
Is the Slö stereo?
No — one input, one output, mono only. Premier Guitar listed “mono only” as a con, and one owner summed up the common sentiment: “Too bad it’s not stereo… I also use it for synths. Maybe I need two…” The Slöer is the stereo model.
Does the Slö have presets?
No. The Slötvå adds three saveable presets and is otherwise sonically identical; the Slöer has three as well. Presets are the single most requested Slö feature.
What does the X knob do?
Something different in each algorithm. In Dark it sets the level of the -1 octave signal feeding the reverb; in Rise, how long the reverb takes to swell in after a note; in Dream, the depth of vibrato on the reverb trail. One knob, three unrelated jobs — the pedal’s cleverest and most confusing decision.
How do I change the modulation wave shape?
Hold down the bypass footswitch and move the algorithm toggle. The three positions then select Sine, Warp and Sink instead of Dark, Rise and Dream. Hold bypass and turn the Depth knob to set modulation rate instead of depth. Both settings are stored per algorithm.
How do I switch trails on or off?
Hold the bypass switch down for one second while applying power to the pedal. Unplug the power and repeat the process to switch back. There is no visual indication of the current mode, so if you buy used, set it yourself.
Slö or Slöer — which should I buy?
If you run mono and do not obsess over noise, the Slö at $186.99 gets you the great majority of the sound for roughly $110 less. If you run stereo, the Slöer is not optional — testers who own both compare running it in mono to “driving a Ferrari, but reducing its top speed by 30%.” If you want the Slö’s sound with presets and can find a Slötvå near $130, that is the sharpest value in the family.
Did The Edge, John Mayer or Mark Lettieri use a Slö?
No — none of the three has any documented Slö usage. Mark Lettieri is a genuine Walrus user, but the pedal he has been photographed with is the Julia chorus, not this reverb. The verified Slö roster is led by MONO’s Takaakira Goto and Hideki Suematsu, Mateus Asato, Alicia Bognanno of Bully, Joe Langridge-Brown of Nothing But Thieves, Soccer Mommy, Will Swan of Dance Gavin Dance, Doyle Martin of Nothing, Eli Maiman of Walk the Moon and NARASAKI of Coaltar of the Deepers.
The Verdict, Seven Years On
The Slö is not the best reverb pedal you can buy for $187, nor the most versatile — an RV-6 covers more ground with less hiss. What it is, is the most specific: three algorithms that each do one thing extremely well, a sustain switch that turns the pedal into a performance instrument rather than a set-and-forget utility, and a lower-octave mode nobody has convincingly copied at this price.
Seven and a half years in, superseded twice by its own manufacturer, it is still in the Core Series, still holding 80% of its value used, still on boards belonging to MONO, Nothing But Thieves and Bully, and still, in one owner’s words, “post rock in a box.” That is a durable record for a two-hundred-dollar digital pedal, and it earns the Slö its place in the ranking.