Carl Martin Contour and Boost EffectsCarl Martin Contour & Boost is especially designed to boost up, and change the sound (contour) of electric guitar bass. The Contour & Boost circuitry is of phase linear design, using high quality components. This ensures sonic clarity and midrange emphasis which is so important for electric guitar. The Contour & Boost is designed as a High Pass (low cut) and Low Pass (high cut) filter, with a fixed X over frequency at 440Hz. The High Pass filter