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An electrostatic pickup converts mechanical motion to an electrical
Wurlitzer Electrostatic Organs by Eric Larson
{{DEFAULTSORT:Electrostatic Pickup Musical instrument parts and accessories
signal
In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The '' IEEE Transactions on Signal Processing' ...
by means of varying electrical capacitance
Capacitance is the capability of a material object or device to store electric charge. It is measured by the change in charge in response to a difference in electric potential, expressed as the ratio of those quantities. Commonly recognized are ...
. This type of pickup, in which the moving plate is a vibrating metal reed
Reed or Reeds may refer to:
Science, technology, biology, and medicine
* Reed bird (disambiguation)
* Reed pen, writing implement in use since ancient times
* Reed (plant), one of several tall, grass-like wetland plants of the order Poales
* ...
, is used in some types of electronic piano
An electronic piano is a keyboard instrument designed to simulate the timbre of a piano (and sometimes a harpsichord or an organ) using analog circuitry.
"Electronic Piano" was also the trade name used for Wurlitzer's popular line of electric ...
s and organs as an inexpensive method of generating tones.
Principle of operation
The electrostatic pickup consists of acapacitor
A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals.
The effect of ...
with one stationary plate and one moving plate. The moving plate is typically a steel or brass reed
Reed or Reeds may refer to:
Science, technology, biology, and medicine
* Reed bird (disambiguation)
* Reed pen, writing implement in use since ancient times
* Reed (plant), one of several tall, grass-like wetland plants of the order Poales
* ...
, anchored at one end and free to vibrate at the other end. Another fixed plate is suspended near the vibrating reed, but is electrically insulated.
A high voltage is applied between the stationary and moving plates to produce an electric field. The motion of the moving plate induces a varying current through the capacitor formed by the reed and the fixed plate.
The capacitance of the pickup is changed by the motion of the moving plate. As a result of the changing capacitance, a varying current flows into or out of the plates as needed to maintain the proper charge for the new amount of capacitance. This current produces a varying voltage across an external resistor which is amplified to produce a usable output signal.
Variations
The shape, size and position of the fixed plate relative to the reed has an effect on the capacitance change as a function of the reed's instantaneous position during its travel. This allows different combinations ofovertone
An overtone is any resonant frequency above the fundamental frequency of a sound. (An overtone may or may not be a harmonic) In other words, overtones are all pitches higher than the lowest pitch within an individual sound; the fundamental i ...
s to be generated from a single reed by placing several fixed plates in different locations, as seen in Wurlitzer
The Rudolph Wurlitzer Company, usually referred to as simply Wurlitzer, is an American company started in Cincinnati in 1853 by German immigrant (Franz) Rudolph Wurlitzer. The company initially imported stringed, woodwind and brass instruments ...
electrostatic organs.
The electrostatic pickup used in the Hohner Pianet
The Hohner Pianet is a type of electro-mechanical piano built by the Hohner company of Trossingen, West Germany and designed by Ernst Zacharias. The Pianet was a variant of his earlier reed-based Hohner electric piano, the Cembalet, which, lik ...
N electric piano has a fixed plate mounted at a 90 degree angle to the reed, while the fixed plates used in Wurlitzer electrostatic organs are parallel to the reed. The position of the fixed plate in the Pianet is such that the capacitance changes most dramatically when the reed is in the upper portion of its travel. The result is a large second-harmonic content in the resulting signal, similar to that produced by a fuzz box
Distortion and overdrive are forms of audio signal processing used to alter the sound of amplified electric musical instruments, usually by increasing their gain, producing a "fuzzy", "growling", or "gritty" tone. Distortion is most commonly ...
distortion pedal.
See also
*Electrostatic reed organ
An electric organ, also known as electronic organ, is an electronic keyboard instrument which was derived from the harmonium, pipe organ and theatre organ. Originally designed to imitate their sound, or orchestral sounds, it has since developed ...
** Everett Orgatron
An electric organ, also known as electronic organ, is an electronic keyboard instrument which was derived from the harmonium, pipe organ and theatre organ. Originally designed to imitate their sound, or orchestral sounds, it has since developed ...
* Compton organ
John Compton (1876–1957), born in Newton Burgoland, Leicestershire was a pipe organ builder. His business based in Nottingham and London flourished between 1902 and 1965.
Life
John Compton was educated at King Edward's School, Birmingham and ...
* Wurlitzer electric piano
The Wurlitzer electronic piano is an electric piano manufactured and marketed by Wurlitzer from the mid-1950s to mid-1980s. Sound is generated by striking a metal reed with a hammer, which induces an electric current in a pickup. It is concept ...
* Hohner Pianet
The Hohner Pianet is a type of electro-mechanical piano built by the Hohner company of Trossingen, West Germany and designed by Ernst Zacharias. The Pianet was a variant of his earlier reed-based Hohner electric piano, the Cembalet, which, lik ...
References
*External links
Wurlitzer Electrostatic Organs by Eric Larson
{{DEFAULTSORT:Electrostatic Pickup Musical instrument parts and accessories