Posted: 25 February 2011
Pick-ups are prominently displayed on most electric guitars, usually directly under the strings and attached to the body of the guitar. And whether they are single coil or humbucker pick-ups, they are almost always magnetic, which produce sound by creating a magnetic circuit between the magnet that is the pick-up and the metal strings. Amplifying an acoustic instrument however, can be a different beast entirely.
Since the sound of an acoustic instrument is produced entirely by the vibration of the strings in relation to the body of the instrument, magnetic pick-ups do not provide the best method of reproducing these vibrations for amplification purposes. As such, a different kind of pick-up known as a piezo pick-up is commonly used to amplify acoustic instruments.
Instead of using magnets, piezo pick-ups react to the vibration of the strings of an instrument. Usually made of polymers, these pick-ups create an electric charge related to the amount of pressure applied to them (through vibration of the strings), which is then transferred to an amplifier or PA system.
In acoustic-electric guitars with a built-in pick-up, piezo pick-ups are usually inside the bridge of the instrument, where the greatest amount of vibration occurs. These are rarely seen, as they are usually placed under the saddle of the bridge and out of sight. But guitars do not provide the only use for piezo pick-ups, as they can be used with most acoustic stringed instruments, such as violins, cellos and upright basses.
Piezo pick-ups also reduce the possibility of feedback, which is high when using magnetic pick-ups on acoustic instruments. Certain brands of piezo pick-ups are built as external pick-ups, which are placed on an instrument (again, usually near the bridge) and connected to an outside amplification system.
While usually the best pick-up option to most faithfully recreate an acoustic instrument’s sound for amplification purposes, piezo pick-ups still lack the ability to completely recreate the resonance of an instrument. This being the case, they are often only used in live settings when mic-ing an instrument is impractical. For studio recordings, most musicians and recording engineers continue to rely on condenser microphones to obtain optimal sound for these instruments.