MAXON SD-9 SONIC DISTORTION distortionThe SD9 has become a legend since it came out in 1980. Wide variety of distortions, from punchy overdrive to striking fuzz, with a complete frequency response, minimum tone coloring and a huge 42dB gain. When most overdrive and distortion pedals have circuit that either cut or boost high frequencies, the SD9 uses a circuitry that cuts or boosts low frequencies.