Darkglass Duality Dual Fuzz Engine

The Darkglass Duality Dual Fuzz Engine is a fuzz pedal for bass, first released in 2013 by Darkglass Electronics¹. What sets it apart from most fuzzes is that it contains two distinct fuzz circuits running in parallel, and you can blend them together in any ratio, then mix the result with your clean signal²¹. One side is a gated, sawtooth-style fuzz with a thick, classic character; the other is a tighter, more modern high-gain fuzz². The Duality knob pans between them, so you can sit on one circuit, the other, or any mix of the two³.

The pedal is classily presented in a brushed silver matte finish with a mirror chromed top facing, and its styling mirrors the company's Microtubes Vintage, but with a darker hue²⁴. It is now the predecessor of the Duality DFZ, which Darkglass launched in November 2022 as its successor⁵.

Two fuzz circuits blended with your clean bass

The core idea of the Duality is that fuzz for bass works best when you keep some of your clean low end in the mix. The pedal offers two distinct fuzz circuits, which can be blended any way you choose with your clean signal². Premier Guitar's reviewer found that its low-pass filter and blend control enable precise low-end sculpting and exceptionally tight and punchy fuzz, and that the pedal was very clearly built to address the shortcomings bass players encounter when adapting guitar fuzz to their instrument⁴.

The two circuits have distinct characters:

• Left extreme (Duality knob): a gated sawtooth circuit, a thick, classic sounding fuzz². Premier Guitar described it as a gated, sawtooth sound⁴.
• Right extreme: a more modern, tighter high-gain sounding fuzz, which Darkglass itself describes as tighter high-gain fuzz²⁴.
• In between: mixes of the two fuzz circuits across the pan².

Aion FX, which traced the circuit in 2021, characterizes the first path as an aggressive but articulate and versatile drive tone, and the second as all-out square wave mayhem, complete with heavily gated "velcro" tones characteristic of misbiased transistors⁶. Pedal of the Day's 2015 review summed up the two circuits as a gated sawtooth wave and a raunchy high-gain sound³.

The controls: Duality, Blend, Level and Filter

The pedal has four black control knobs plus a stomp button, and the controls are logically arranged with a smooth feel²⁴. Each knob does one clear job:

Aion FX's trace adds detail on how the controls sit in the circuit: the volume control only applies to the fuzz signal, and the combination of the effect volume and the clean blend provides extra fine-tuned mixing capability⁶. In bypass mode, the blend knob is hard-wired to 100 percent, so the pedal passes your clean signal⁶.

The soft switches Darkglass uses are quiet to operate; Pedal of the Day's reviewer wrote that "you can stomp all over them barefoot and not even notice"³.

Inside the circuit: CMOS stages and a comparator fuzz

Aion FX traced the Duality's circuit in 2021, and the trace explains why the two fuzz paths sound so different¹⁶.

The first fuzz path is a cascade of overloaded CD4049UBE hex inverter stages providing the distortion, with three CMOS stages⁶. This is the aggressive but articulate path, and Aion FX notes it sounds pretty similar to Darkglass's flagship Microtubes B3K⁶.

The second fuzz path is built differently: a single op-amp stage configured as a comparator, with the signal going to the inverting input, the non-inverting input tied to a reference voltage, and no feedback path⁶. The comparator is followed by a primitive two-diode noise gate to keep it quiet when no signal is coming through, and those diodes also add crossover distortion⁶. This is the source of the heavily gated "velcro" tones⁶. Aion FX notes the comparator concept is similar to Craig Anderton's "Ultra Fuzz," first published in Electronics Project for Musicians in 1978, though the Duality's comparator threshold is fixed rather than variable⁶.

The bypass is a fairly standard JFET flip-flop design, only using the CD4049 instead of transistors like Boss or Ibanez use⁶. Aion FX also found one quirk that has stayed the same across at least seven PCB revisions: a capacitor that forms a 16kHz lowpass filter, which does basically nothing in this application and is likely a design mistake⁶. Revision 7 added R11, a 1M bias resistor at the input of the opamp buffer stage after the CMOS inverters, which Aion FX calls an editorial change rather than a tonal tweak, suggesting the revisions were primarily layout optimizations⁶.

What reviewers said

Published reviewers were positive about the Duality. MusicRadar called it "a real winner from Darkglass, impressively simple to use but very effective"². Premier Guitar's verdict was "big and versatile fuzz tones in a small box"⁴. The Premier Guitar review tested the pedal with a Nash P-Style bass through an Epifani AL 112 combo, and later with a 1964 Fender J bass paired with a Boss OC-2⁴.

The Duality and the Duality DFZ

The Duality Dual Fuzz Engine was first released in 2013¹. Its single duality dial is the heart of the pedal: panned fully left it initiates the gated saw-tooth circuit, a thick classic sounding fuzz, and panned fully right it gives what Darkglass describes as tighter high-gain fuzz, with mixes of the two across the pan². Reviewers found it impressively simple to use but very effective, calling it "a real winner"².

Videos

Click to load

Click to load

Click to load

Questions