Walrus Audio Silt

The Walrus Audio Silt is a fuzz pedal built around a real 12AU7 preamp tube. Walrus Audio describes it as a two-in-one fuzz: an analog circuit with the warmth of a 12AU7 tube as its drive section, plus a Harmonic mode that adds an octave-up before the fuzz¹. It was announced on 16 January 2024, ahead of NAMM, and designed in collaboration with tube expert Jim Hagerman of Hagerman Amplification².

A fuzz driven by a 12AU7 tube

Most fuzz pedals get their sound from transistors or clipping diodes. The Silt instead uses an internal 12AU7 preamp tube as its drive section, and the fuzz comes from pushing that tube hard. Guitar.com's reviewer, Cillian Breathnach, found no clipping diodes in the circuit, so the fuzz comes mainly from driving the 12AU7 far beyond its headroom⁵. Delicious Audio notes that pedals with tubes in them are quite rare, and normally confined to the overdrive niche, which makes a tube-based fuzz an unusual design⁸.

The tube is fully enclosed within the pedal but visible through a transparent window, so it is protected while still on display⁵. In the worst case of a failed tube, the manual outlines the simple steps needed to replace it⁵.

As for how it sounds, Guitar.com's reviewer described the base fuzz as:

That is not a low-gain, dynamic fuzz. It is a loud, compressed, midrange-forward sound, which the reviewer found works well for chords and rhythmic parts⁵⁴.

The controls and the three-way filter

The Silt keeps its control set simple: Volume, Tone and Gain knobs, a Contour toggle, and two footswitches, one for bypass and one for Harmonic mode⁹.

The Contour toggle is the most useful control for fitting the pedal into a rig. Delicious Audio describes the three positions as delivering full response (flat), tight and sparkly (low-pass), or warm and bassy (high-pass) tones⁸. Guitar.com's reviewer found the three filter modes help the Silt sit well in a full signal chain⁵. Walrus also suggests the pre-tube EQ stage is helpful when switching between different styles of pickups².

The Tone control is worth noting for experienced players: it is an active tilt EQ, boosting and cutting highs and lows rather than just passively filtering the whole signal⁵.

Harmonic mode: an octave-up before the tube

The second footswitch engages Harmonic mode, the "harmonic" part of "harmonic fuzz". Walrus Audio describes it as a frequency doubler placed before the drive section of the pedal, producing crispy, octave-like sounds¹. Guitar.com's reviewer calls it an analog octave-up before the main fuzz circuit, in the tradition of the Dan Armstrong Green Ringer or the Univox Superfuzz⁵.

A few things a player should know about Harmonic mode:

• There is no blend control for it. Guitar.com's review notes there is no blend control for Harmonic mode, "nor does there need to be"⁵.
• Walrus Audio recommends rolling back the guitar's Tone knob when engaging the mode⁹.
• The frequency doubler circuit adds a uniquely crisp quality to the signal, reminiscent of upper octaves⁸.

Power: 9V or 12V, 300mA

The Silt runs on 9V DC, center negative, with a 300mA minimum current draw¹. It can also be powered at 12V, which delivers extra gain and a little more volume output, though Guitar.com's reviewer found it plenty loud at 9V⁵⁸.

Designer, colorways and editions

The Silt was created in collaboration with tube expert Jim Hagerman of Hagerman Amplification⁸. Walrus Audio calls it a collaborative creation with Hagerman, who is known for his tube amp work⁴⁶⁸.

It launched in two colorways at the same price of $299 in the US and £289 in the UK⁶:

• Red: a full dinosaur skeleton design, with artwork from Adam Forster⁶¹⁰
• Matte black: a more minimalist single dinosaur claw design⁵

Guitar.com's reviewer found the build quality solid and feeling very premium, though the matte-black finish is an absolute fingerprint magnet⁵.

There was also a limited Black Friday 2024 Floral Series edition of the Silt, sold as a blemished unit, which is now sold out⁴.

What reviewers said

Guitar.com's review found the Silt's base fuzz mode is not a low-gain dynamic preamp fuzz: it is a thick, smooth distortion that's quite compressed, very loud, and very midrange-heavy⁵. The same reviewer found the build quality solid, though the matte-black finish is a fingerprint magnet⁵.

Guitar World's review listed the Silt's flexible EQ among its strengths⁷. The pedal was created in collaboration with tube expert Jim Hagerman of Hagerman Amplification, and Walrus Audio notes that pedals with tubes in them are quite rare, and normally confined to the overdrive niche⁸.

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