ABSTRACT
The standard electric guitar technology uses the vibrations of a ferromagnetic string to modulate the magnetic field seen by the pickup windings. Both standard and humbucking guitar pickups have several thousands of turns in the coil to get an adequate output, which also means a substantial series inductance. Guitar preamplifiers need to have variable gain, suitably low noise and a high input impedance to prevent roll-off of HF content. The noise calculations for a guitar preamplifier are simple compared with the equivalent for MM cartridges or tape preamplifiers because there is no equalisation to complicate things. Electric guitars are traditionally operated into valve amplifiers, often with integral loudspeakers. The amplifier distortion and the frequency response of the speaker can radically alter the sound to the extent that it is sensible to regard the guitar/amp combination as a single instrument. Direct injection refers to running the guitar output directly into a mixing console without the use of an amplifier.
