Stefan Karlsson

Stefan Karlsson is the writer behind Guitar Pedal X, a blog that reviews new fuzz, overdrive, distortion and modulation pedals, publishes buying guides, and names year-end best-of selections. He is best known in the pedal community for the scale of his reference collection: over 1,300 pedals, of which well over 700 are fuzzes¹. When a new fuzz arrives, he uses that collection as his measuring stick. As he puts it, "I have well over 700 fuzzes in the reference collection by now - so I always like to see which circuits it sits close to, and what aspects of it are entirely unique!"²

He describes himself plainly as a noise maker: "I own over 700 fuzzes - and this is an entirely new variety for the collection"³. His writing covers new releases from small builders and major brands alike, and his own buying habits show up throughout it, which makes his reviews an unusually detailed record of what one player actually owns and uses.

The reference collection

The collection is organized around circuit families, and the Big Muff type is the largest. Karlsson reported more than 110 Big Muff types in June 2024¹, and by August 2026 the count had passed 130: "the most populous genre category within my reference collection has become the Big Muff type - where I now have over 130 pedals of various sizes"⁴. New entries still get logged against the tally; reviewing the Walrus Audio Eons fuzz in 2022, he noted that "it may be a sort of Multi-Fuzz - but it will also be my 98th Big Muff!"⁷

Fuzz Faces are the other big family, and the count has climbed steadily:

Within that group he owns four of SGFX's If 6 Was 9 Fuzz Face variants, including the limited Germanium edition and the recent BC183 edition⁸, and five of the nine pedals in his own mid-size Fuzz Face buying guide: the Palmer Custom Effects Solarist V2 and Solarist Green, Red Witch Fuzz God IV, Silktone Fuzz, and ThorpyFX The Veteran Si⁸. Tone Bender variants sit somewhere over 50¹.

Beyond fuzz, the collection branches into several other circuit families he tracks deliberately:

• Boss gain pedals: he owns all of them in their original formats, alongside multiple modded and special editions of each¹⁰
• Dumble-style drives: around 20, a format he collects separately¹¹
• Tremolos: 35 to date as of April 2026¹²
• PLL pedals: about half a dozen, with the Beetronics Swarm and Tark Audio SquidInk named as his favorite takes¹³
• Chase Bliss: 20 pedals, the Brothers AM being the twentieth¹⁴
• Spaceman Effects: 17 pedals overall, 8 of them fuzzes¹⁵
• Rat-style pedals: the JHS PackRat was the 33rd Rat in his collection¹⁶
• Mini Muffs: 7 owned¹⁷
• Hello Sailor Effects: 15 pedals¹⁸
• DOD250 derivatives: he actively collects evolved and extended range versions¹⁹

His board and daily pedals

Karlsson's current rig has 52 pedals in its signal chain, which he routes and combines in several different ways, including syncing effects in parallel through a Parallelarator⁶. He previously used TheGigRig's Wetter Box on the board before switching to the Cosmic Loop Parallelarator wet-dry-wet gateway pedal²⁰. When he first covered parallel blenders in 2020, he favored the original Old Blood Noise Endeavors Signal Blender and TheGigRig's Wetter Box²⁰.

For ambience, he uses the Strymon BigSky MX on his board and has experience with the Meris LVX and the Eventide H90⁶. The Strymon connection goes back years: he has described himself as a daily user of the Mobius, TimeLine and BigSky²¹, and the Empress EchoSystem took over as his day-to-day delay pedal of choice²¹. On the modulation side, the Hamstead Redwing is currently on the board, a stereo modulator he credits with a particularly fine Leslie and rotary style voicing²², and he has used the Thorpy Camoflange flanger and the JAM Pedals Harmonious Monk as his two analog modulations²³. He also owns several Roland Space Echo units²².

His pitch shifting is handled by Boss: he has had both the XS-1 and XS-100 on his board, though the XS-1 is more typically switched out for the PS-6 Harmonist, which he uses for the S-Bend Morello effect and three-part Iron Maiden style harmonies²⁴. On phasers he owns the Mu-Tron Phasor III and the PastFX Foot Phase Deluxe²⁵.

For dirt, he has been a champion of the Chase Bliss Brothers, which he mostly uses as a fuzz, combining its core fuzz voicings with overdrive and boost for a wide range of fuzzy flavors¹⁴. He also owns the Analog.Man King of Tone in a JHS 4-Star modded edition and loves it as an overdrive¹⁴. His ThorpyFX holdings have included the Fallout Cloud, Gunshot and Warthog²⁶, and his Thorpy tally reached five pedals, with The Veteran Fuzz named as the next in line for rotational duties on his number 5 fuzz slot²⁶. He bought the Thorpy Heavy Water dual boost and Peacekeeper V2 together for what he called a turbo-charged experience of The Dane, with Heavy Water planned as principal in his number 8 slot, replacing a Spaceman Mercury IV²⁶.

His Spaceman collection, in chronological order, runs to eight pedals he calls really fantastic: the Sputnik I Germanium Fuzz, Spacerocket Intermodulation Fuzz, Aphelion Harmonic Overdrive, Mercury IV Germanium Harmonic Boost, Titan II Fuzz Machine, Nebula Fuzz and Octave Blender, Polaris Resonant Overdrive, and Gemini IV Dual Fuzz Generator²⁷. He later ordered a White edition Rumblefuzz II, his eighth Spaceman fuzz and seventeenth pedal from the brand overall¹⁵.

Among his Rat-style pedals he owns and loves the Bardic Audio Thunderclap, Big Ear Woodcutter, Dr Scientist Frazz Dazzler, JAM Pedals Rattler, Thorpy FX Warthog, VFE Alpha Dog and Wampler Mini Ratsbane¹⁶, and he has the JHS Muffuletta in its original black and yellow, yellow knob version¹⁶. He also owns four Flower Pedals, the Dahlia, Sunflower, V1 Castilleja phaser and vibe, and V1 Hosta, all of which he considers essential, with the Dahlia fixed to the board for a while²⁸.

Dumble-style drives and favorite makers

Karlsson calls himself a huge fan of the Dumble format and has around 20 Dumble drives, which he collects as their own category¹¹. He preordered the DSM Humboldt Dumblifier from Andertons¹¹, and his current favorite Dumbles are the Ethos Clean Fusion II, Tanabe Zenkudo, Demon Pedals Kondo-Shifuku, Colortone V2 Parasite, and Mad Professor Simble¹¹.

Hello Sailor Effects is a maker he has gone deep on. He went from zero to six of their pedals in a relatively short span²⁹, then picked up three more at the Birmingham Guitar Show¹⁸, reaching fifteen, including three RangeMasters and treble boosters and a Brian May Boost¹⁸. His HSE holdings also include a hybrid germanium and silicon Abbey Road Fuzz and a Free Range, and he credits builder Joe with deploying unique and smart circuit tricks to get more volume and flavor out of both circuits⁸. The HSE Anchor Drive and the Monmouth octave fuzz are two of his very favorite effects²⁹. On treble boosters he is direct: "Everyone should have at least one RangeMaster - and it totally makes sense that it should be a Hello Sailor one!"¹⁸ He has even planned to send Joe his defunct Keeley I Get Around, for the chassis and knobs to be used in another unique creation²⁹.

What he looks for in a fuzz

Two of his stated preferences come up repeatedly in his writing. The first is bias control: "I prefer all my Fuzz Faces and Tone Benders to have external Biases - as it's such a key tool for adjusting the nature and timbre of the fuzz - and gives you more flavours and versatility"⁵. The second concerns Mini Muffs: "I have found that a number of the Mini Muffs can be a little underpowered compared to the compact and larger size editions"¹⁷, meaning some need more output volume. He remains a fan of the format and owns seven, with the Custom Pedal Boards Mini Muff War, with its oddly closely clustered knobs, still to be acquired¹⁷.

The FuzzBillion and his Pedal of the Year picks

Karlsson's most celebrated pick is the Teaching Machines FuzzBillion, an analog multi-gain pedal from a maker known for unique musical devices, with the FuzzBillion its first floor-based guitar pedal³⁰³¹. The pedal uses 11 component and element roulette wheels with an up and down selection mechanism, delivering 11 billion combinations overall, of which he estimates probably only 10 billion are properly usable³². In his view it covers everything from clean to textured boost, through overdrive, distortion, and various styles of fuzz³⁰.

He named it his Pedal of the Year for 2025³³, calling it "one of my all-time favourite pedals" whose "combination wheel gain-shaping delivers myriad exceptional tones across the gain spectrum"³⁰, and at the year-end selection he judged it "a pedal design benchmark for the ages - and wonderful mechanical marvel to boot!"³⁴. Teaching Machines describes the FuzzBillion as the "last distortion pedal you ever need"³¹, a claim Guitar.com's reviewer Ed Oleszko treated with affection while noting how rare it is for one pedal to cover so many bases while adding new points on the map³¹.

His 2026 pick had already taken shape by April, when he wrote of the Dazatronyx Big Fuzz Console: "currently I can't see how this isn't going to end up as my Pedal of the Year - it works superbly well - Darron has done such a good job with this - and it consistently delivers my favourite Big Muff tones - this is for sure the Ultimate Big Muff Pedal, and one of the very best Multi-Fuzzes of all time!"³⁵

Wishlist and buying habits

His wishlist has shifted over the years. In 2019 it held the Spaceman Rumblefuzz Fuzzstortion, Wow Signal Alien Fuzz Communicator and Explorer Deluxe 6 Stage Optical Phaser, which he was waiting to find on Reverb at the right price²⁷; the Explorer Deluxe later arrived in a more compact, pedalboard friendly format²⁵, and the Rumblefuzz II was ordered in its White edition¹⁵. The Holy Island Audio Angel Teeth, an evolved DOD250, had been on his wishlist for years before he acquired it, and the Blast Radius remains his next priority target from that maker, of which he owns three¹⁹. He wanted the Flower Pedals Geranium Germanium Drive but left it too late, so he hopes to find a reasonable condition one used at a sensible price²⁸.

His year-end selections are backed by his own buying: for his 2024 boost and overdrive selection he personally owned 27 of the 35 pedals chosen³⁶. He became a That Pedal Show Patreon because of their special collaboration pedals²³, and he acquired his Chase Bliss Bliss Factory at $399⁸. On new releases he is willing to commit early: reviewing Automat Audio Devices' first two fuzzes, he called them "a very fine, possibly exemplary even first attempt - where I'm intending to go for both of them"².

Questions