Magnetoresistive sensors for string instruments

Abstract

Pickup elements for string instruments, in particular for electric guitars, represent a new application area for magnetoresistive sensors. Recently we developed a sensor configuration with permanent magnets for this purpose. For the first experiments we used commercial anisotropic magnetoresistance sensors (Philips KMZ10) mounted on small ferrite bias magnets. Recently we equipped an electric guitar with prototypes comprising giant magnetoresistance (GMR) sensors. These prototype MR pickup elements showed several clear advantages compared to the presently commonly used inductive pickup units. They are much less sensitive to disturbing electromagnetic fields (>1000×at 5 kHz), mainly because their active sensor area is several orders of magnitude smaller (a few mm2 instead of cm2). Also the larger freedom in the choice of the permanent magnets (due to the larger sensitivity of the GMR elements) is advantageous: employing smaller magnets reduces the damping and thus significantly improves the sustain, the magnets can be less expensive and more stable magnet materials can be chosen so that aging effects are eliminated.