Boss Hyper Fuzz (FZ-2)

The Boss Hyper Fuzz (FZ-2) is a fuzz pedal made by Boss from April 1993 to June 1997¹. Under the hood it is a clone of the Univox Super Fuzz with added circuits around it: a Boss buffer at the input, an active bass and treble stage, and a boost stage that lets the pedal work as a clean gain booster¹². It came in a gray Boss enclosure and has been described by Guitar World as "a sturdy, excellent-sounding Univox Super Fuzz clone beloved of stoner rockers"³.

The pedal is no longer made, and it has since become one of the circuits players most want Boss to bring back. In 2020, Guitar.com reported that the FZ-2 was among Boss's most-requested pedals for a Waza Craft version, alongside the HM-2 Heavy Metal⁴.

What the Hyper Fuzz does

The FZ-2 is an octave fuzz. Like the Super Fuzz circuit it copies, it adds an octave down to your guitar tone, which provides a huge bassy sound, plus a slight octave up that is more audible when playing near the 12th fret¹. The saturation itself comes from two diodes (D4 and D5) doing the clipping, which is the same approach as the Super Fuzz¹.

The pedal has four knobs. Level sets the volume, a second potentiometer sets bass and treble amounts, the gain potentiometer sets the fuzz amount, and the last knob selects between three modes: Fuzz I, Fuzz II and Boost¹.

In Boost mode the pedal can be used purely as a gain booster with no added distortion⁸. Fuzz II is the scooped-sounding mode: Guns N' Roses guitarist Richard Fortus told Boss's own interview series, "I tended to use the FZ-2's Fuzz II mode with the scooped sound"⁹. Guitar.com has described the pedal's overall character as "the scooped doom-ready octave fuzz of the FZ-2"⁴¹⁰.

The pedal found its audience largely in stoner rock and doom circles⁶. Coda Effects notes that the Hyper Fuzz is used by Electric Wizard¹, and producer Tom Dalgety used it for chordal work on sessions for The Night the Zombies Came at Rockfield, finding it "amazing in the boxy-sounding mode with the Gain knob backed off"¹¹.

A Super Fuzz circuit with added stages

Independent circuit analyses agree on the FZ-2's lineage. Aion FX describes the fuzz stage as "a near-exact replica of the [Univox Superfuzz] which brings the thick distortion and octave-up fuzz stage"². The original Univox Super Fuzz runs six transistor stages, Q1 to Q6, with Q4 and Q5 forming the octave section¹².

Boss did not just copy the circuit, though. Coda Effects breaks the FZ-2 down into four distinct parts: boost, fuzz, filter and tone². Around the Super Fuzz core sit:

• A Boss "flip flop" buffer that converts the signal to low impedance at the input¹
• The Super Fuzz circuit itself, with two transistors (Q13 and Q14) facing each other with a common emitter creating the octave sound¹
• A bass and treble control circuit built from four op amps¹
• The mode switch¹

The added circuits before and after the Super Fuzz section reduce the signal/noise ratio problem and increase the final signal, compared with the low output of a vintage Super Fuzz¹. It is a big circuit for a Boss enclosure: a monolayer PCB with components running at least to R62 and C35, using 1/8W resistors to fit everything inside¹.

The transistors are 2SC3378s, old parts that are no longer produced, with a really small amplification factor (hfe) of 50¹. Two operational amplifier ICs handle the bass and treble content¹. For comparison, the original Superfuzz has five transistors¹³.

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