Kupiansk Sub Fuzz

Kupiansk Sub Fuzz is an original, multi-stage fuzz architecture designed to combine dense harmonic saturation with seismic, synth-like low-end tracking. At the front end, an NOS Soviet KR574UD2V dual op-amp drives two radically different clipping stages in series: a non-inverting first stage featuring asymmetrical soft clipping via an NOS Soviet AL103 LED and dual KD522 silicon diodes, followed immediately by an inverting second stage pushed into discrete transistor hard clipping. This cascading topology creates a massive, razor-sharp wall of fuzz that retains precise pick attack, exceptional string separation, and singing sustain even under heavy gain.

Parallel to the main dirt path, the signal is routed through dedicated pre- and post- Sallen-Key active filters engineered to condition the frequency response for an NOS Motorola MC14024 CMOS binary counter. The IC extracts independent -1 and -2 analog sub-octave signals that track cleanly across melodic single notes and collapse into aggressive, glitching sub-synth chaos under dynamic attack. With independent level controls for both sub-octaves and the core fuzz, the circuit moves effortlessly from thick doom-laden sludge to pulverizing monophonic synth textures without collapsing into low-end mud.

• Fuzz - adjusts overall gain across both clipping stages.
• Volume - sets the output level.
• Octave -1 - bends in the analog one-octave-down square wave.
• Octave -2 - blends in the deep two-octaves-down sub-bass signal.
• LED brightness trimmer - placed on the PCB trimmer allows you to adjust the status LED brightness.

Named after the strategic railway hub of Kupiansk in the Kharkiv region, a city that has repeatedly demonstrated unmatched resilience on the front lines. Its critical junction history parallels the circuit's dual-path architecture — splitting raw signal into parallel filtered streams before slamming them back together into an uncompromising, heavy sonic force.

9V DC adapter (Boss-style negative center) not included. No batteries. They are bad for the environment 🌲.

Voltage: 9V

Current draw: 12.0 mA

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