Music – Instruments – Electrical musical tone generation
Reexamination Certificate
2000-05-19
2001-08-07
Witkowski, Stanley J. (Department: 2837)
Music
Instruments
Electrical musical tone generation
C084SDIG002
Reexamination Certificate
active
06271457
ABSTRACT:
FIELD OF THE INVENTION
This invention concerns a pickup or electro-mechanical transducer for converting the vibrations of one or more strings of a stringed musical instrument into electrical signals and of the type wherein the pickup has for each string at least one piezoelectric crystal forming part of the instrument bridge and arranged to be excited by the string vibration, and deals more particularly with such a bridge-type piezoelectric pickup having an improved construction and performance in comparison to previously proposed pickups of such type.
BACKGROUND OF THE INVENTION
Although many different constructions of bridge-type piezoelectric pickups have been proposed and used in the past, such pickups have often been subject to one or more troubling deficiencies such as difficult and time-consuming assembly requirements, excessive weight or mass, susceptibility to the introduction of noise or interference into the signal transmission system, excessive cross-talk in signals from nearby strings, and weak output signals resulting in frequency response losses as the signals are transmitted to remote amplifying circuits. A further difficulty often is the inability to easily selectively adapt a given multiple string pickup to have either a single monaural output or a multiple channel output, or to be responsive to different modes of string vibration.
The object of the present invention is, therefore, to provide an improved bridge-type piezoelectric pickup which, among other desirable things, significantly reduces or overcomes the above-mentioned deficiencies of prior pickups.
SUMMARY OF THE INVENTION
The invention resides in a bridge-type piezoelectric pickup for use with a stringed musical instrument, such as a guitar, mandolin, lute, violin or the like, having a body with a top surface and at least one stretched string extending over the top surface and supported at one point by a bridge located between the top surface and the string with the bridge holding the string in a somewhat deflected condition so that the string presses downwardly on the bridge. An individual string-engaging saddle is provided for each string and at its lower end rests on a set of two piezoelectric crystals arranged at different locations along the length of the string so that the two crystals are excited in a common or in-phase way by the movement of the saddle, arising from vibration of the string in a plane perpendicular to the string, and are excited in a non-common or out-of-phase way by movement of the saddle arising from vibration of the string in the longitudinal direction of its length. The use of the pair of crystals and a separate saddle for each string minimizes cross talk between nearby strings. In addition, neighboring pairs of crystals are advantageously connected out of phase with one another to further reduce cross-talk signals from adjacent string excitation.
The invention also resides in the pickup having an active semiconductor circuit, such as an operational amplifier, located in close proximity to and electrically connected with the piezoelectric crystal set of each string to provide a high impedance input for the electrical signal produced by the crystal set, and some amplification may also be provided by the active semiconductor circuit or operational amplifier or by an associated amplification stage forming part of the pickup, so that the output signal can be transmitted efficiently from the pickup to a remotely located supporting circuitry without significant frequency response losses and/or the accumulation of significant amounts of hum or other noise or interference by the transmitted signal.
The invention also resides in the piezoelectric crystals, operational amplifiers and other electronic components of the pickup being carried by a circuit board, by the circuit board advantageously being a flexible one, and by the piezoelectric crystals and other electronic components being attached to the circuit board by surface mount technology techniques so as to facilitate the assembly of the pickup. In keeping with this, the two piezoelectric crystals of each set are advantageously “transversely-polarized” ones with each having two vertically spaced horizontal excitation faces between which the crystal is compressed by forces from the associated string and two horizontally spaced vertical voltage signal terminal faces, so that the two voltage signal terminal faces of each crystal can be directly connected to the upper surface of the circuit board, as by surface mount soldering. Also, the flexible circuit board preferably has an elongated tail portion, with electrical conductors, extending from the body of the pickup, which tail portion can be inserted through a hole in the top plate of the instrument for electrical connection to a power supply, preamplifier, and/or other module located within the instrument body.
A further feature of the invention is that the circuit board is thin and its bottom surface is exposed in relation to other parts of the pickup so as to directly engage the top surface of the instrument with which the pickup is used, to provide a beneficial direct and firm transmission of the vibratory forces of a string to the associated set of piezoelectric crystals, and through those crystals to the instrument top.
The pickup of the invention not only reduces cross-talk and frequency response losses and is of a simplified construction, but also when used to provide multiple independent signal channels, that is, one independent signal channel per string, also allows for individual tailoring of signal equalization as well as other individual signal processing, and provides the basis for multi-channel analog to digital conversion and attendant digital signal processing techniques and control functions afforded in the digital domain. For example, one or a selected set of strings can be selected for reproduction, different string signals can be amplified or otherwise modified in different ways, or different string signals can be amplified and sent to different speakers for reproduction.
Other features and advantages of the invention will be apparent from the following detailed description of a preferred embodiment of the invention, and from the accompanying drawings and claims.
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Kaman Music Corporation
McCormock, Paulding & Huber LLP
Witkowski Stanley J.
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