Darkglass Harmonic BoosterHarmonic Booster 2. 0 The mythical design that started it all is back! The Harmonic Booster was our first design ever. In our quest to design the perfect bass distortion, first, we had to master the control of harmonics and filtering, which are crucial to sculpting the character and texture of a distortion circuit at will. It was then when testing the first few gain and filter stages of what would later become the core of our overdrive technology that