An electric violin is a violin equipped with an electronic output of its sound. The term most properly refers to an instrument purposely made to be electrified with built-in pickups, usually with a solid body. It can also refer to a standard violin fitted with an electric pickup of some type, although "amplified violin" or "electro-acoustic violin" are more accurate in that case.
Electrically amplified violins have been used in one form or another since the 1920s; jazz and blues artist Stuff Smith is generally credited as being one of the first performers to adapt pickups and amplifiers to violins. The Electro Stringed Instrument Corporation, National Valco and Vega attempted to sell electric violins in the 1930s and 1940s; Fender produced a small number of electric violins in the late 1950s. Larger scale manufacture of electric violins did not happen until the late 1990s.
Acoustic violins may be used with an add-on piezoelectric bridge or body pickup. To avoid feedback from the resonances of the hollow body under high amplification on stage, many instruments have a solid body instead. The timbre (tone color) of a standard unamplified violin is due in large part to these resonances, however, so depending on how the signal is picked up, an electric violin may have a "rawer" or "sharper" sound than an acoustic instrument. This raw sound is often preferred in rock, pop, and some avant-garde genres. Several "semi-hollow" designs exist, containing a sealed but hollow resonating chamber that provides some approximation of acoustic violin sound while reducing susceptibility to feedback.
Solid-body electric violins typically have a non-traditional, minimalistic design to keep weight down.
They are often seen as "experimental" instruments, being less established than electric guitar or bass. Hence, there are many variations on the standard design, such as frets, extra strings, machine heads, "baritone" strings that sound an octave lower than normal, and sympathetic strings.
Acoustic 5-string violins exist, but it is much more common for an electric violin to have 5, 6 or 7 strings than an acoustic instrument. The typical solid body also accommodates the extra tension caused by more strings without stressing the instrument too much. The extra strings are usually a low C string for 5-strings, a low C and low F for 6, and a low C, F and B-flat for 7.
Electric violin signals usually pass through electronic processing, in the same way as an electric guitar, to achieve a desired sound. This could include delay, reverb, chorus, distortion, or other effects.
Electric violins commonly use either magnetic or piezoelectric pickups. Magnetic pickups require the use of violin strings that have ferrous (iron-containing, as in steel) metal cores. A few single-coil guitar-style magnetic systems are available, and one unusual acoustic/electric violin system uses the strings as a linear active pickup element. This circumvents the problem that the small body size and arced string arrangement of a violin often limit the amount of space available for coil placement.
Generally, piezoelectric pickups are more common. They detect physical vibrations directly, sometimes in or on the body, or in some cases actual string vibrations directly, but more commonly general bridge vibrations are sensed. Some piezo setups have a separate pickup (or two, or even four in the case of some Barbera Transducer Systems pickups) within the bridge under each string. A few systems use transducers oriented in various directions to differentiate between bowed and plucked string motion.
Piezo pickups have a high (capacitive) output impedance, and must be plugged into a high impedance input stage in the amplifier or a powered preamp (a charge amplifier is best). This buffers the signal to avoid low frequency loss and microphonic noise pickup in the instrument cable. Preamplification is often done by an external signal processor, but some electric violin body designs can provide internal housing for preamp circuitry.