Why are active bass guitars preamplified?
A pickup consists of a copper wire coil wound around a magnet. It works on the principle of electromagnetic induction, which is caused by the motion of the string in the magnetic field above the pickup. To keep it simple, the vibration of the metal string produces an electric current corresponding to its oscillation frequency.
Until the seventies, guitar and bass pickup manufacturers were not able to build more powerful pickups. The technique used to increase gain was to increase the magnet size or the windings around the magnet. But unfortunately:
- Oversized magnets affect string vibration
- Too many windings cause strong radiations which capture both string vibration and unwanted noise.
Back in 1969, Alembic's founder, Ron Wikersham, had a good idea: to create the first low-impedance bass-guitar pickup. A brilliant solution: Ron's pickups had a small number of windings, which also resulted in a low output gain (less radiations, less unwanted noise). The system included an internal preamp (built inside the instrument) to boost the low-gain signal. This innovation brought many advantages with itself and would revolutionize the bass-guitar world.
