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The Concrete Sound Lab Slab is an all-transistor gain pedal designed to produce a range of tones from cleanish overdrive to saturated fuzz.

Its circuit combines a JFET-based preamp with a James tone stack—a configuration that allows precise control over frequency response before the signal hits the gain stage. This feeds into a silicon bipolar transistor output section, which provides dynamic response and harmonic complexity.

The design prioritizes responsive, lo-fi distortion with usable tone shaping at any gain level.

The preamp’s tube-like response works well with both guitar and bass, while the post-gain filter ensures the distortion remains usable even at high gain settings.

Features:

  • Boost footswitch adds extra saturation
  • Pre-gain tone stack shapes the character of the distortion
  • Post-gain low-pass filter tames high-end harshness