Wireless amplification system for musical instruments

A wireless sound transmission system for musical instruments includes a transmitter which can be mounted within the hollow body of the instrument. The transmitter is provided with a clamp which positions it adjacent the sound hole through which it is inserted. The transmitter may have a face contained to follow the outline of the sound hole. In a first embodiment, the transmitter is adapted to be mounted through and proximate a round sound hole. In a second embodiment, the transmitter is adapted to be mounted through an f sound hole.

The present invention relates to the electrical arts and, in particular, to 
an apparatus for providing amplification to the sounds of certain musical 
instruments. 
BACKGROUND OF THE INVENTION 
The use of sound pickups and amplification devices in connection with 
musical instruments is well known. The so-called "electrical" guitars, for 
example, are provided with electrical pickup means which convert the 
sound-generating string vibrations into an electrical signal which, 
typically by use of a cable from the instrument, is passed to an 
amplification and reproduction unit. Because the electrical pickups serve 
as part of the primary sound generating system for the instrument, the 
guitar is constructed in a manner directed to that end. Its acoustic 
properties are substantially different from those of a traditional, 
"non-electric", instrument. 
In addition to instruments, such as the electric guitar, which are 
specifically designed for electronic amplification, a variety of devices 
have been developed for electrical amplification of the sounds of 
conventional acoustic instruments. Such devices typically include a 
microphone-type pickup mounted to the instrument body, either hard wired 
to a remote amplification device or, preferably, coupled to a wireless 
transmitter which broadcasts the signal to a receiver at the amplification 
site. Such a setup presents a more aesthetically pleasing methodology, 
typically avoiding long cable runs and allowing more flexibility in the 
positioning of the amplification equipment vis-a-vis the performer. 
To insure sufficient coupling between the sound generated by the instrument 
and the pickup device, the sound pickup unit is preferably mounted 
directly upon the instrument. While the means by which the pickup is 
mounted to the instrument and its placement on the instrument may be of 
little concern to the average player, highly skilled performers, utilizing 
instruments often valued at many thousands of dollars, are vitally 
concerned that the pickup be positioned on the instrument so as to most 
properly and fully receive and transmit the instrument's sounds in a 
manner faithful to their generation, while not significantly affecting the 
tonal response of the instrument. In addition, it is of great importance 
that the device both be non-obtrusive when placed on the instrument and 
that it does not in any way cause damage to the instrument. 
It is accordingly a purpose of the present invention to provide a wireless 
transmission system for sounds developed by musical instruments. 
Yet another purpose of the present invention is to provide a wireless 
transmission system capable of being mounted upon an instrument in an 
unobtrusive manner, without significantly modifying the tonal response of 
the instrument or causing damage or mechanical alteration thereto. 
Still another purpose of the present invention is to provide a wireless 
transmitter for a musical instrument which may be easily installed upon 
and recovered from the instrument and which will remain in place to 
provide high fidelity, full tonal pickup with respect thereto. 
DESCRIPTION OF THE INVENTION 
In accordance with the above and further objects and purposes, the present 
invention comprises a wireless transmitter adapted for mounting to an 
instrument, through utilization of the instrument's sound hole or other 
appropriate part of the instrument's resonating chamber. A remote receiver 
receives the transmission and converts it into an electrical signal which 
may be amplified as known in the art. 
In a first embodiment, the transmitter is particularly adapted for use with 
an acoustic guitar, utilizes the instrument's sound hole for mounting 
purposes and consists of a miniaturized housing in which a microphone, 
radio-frequency transmitter and power supply are mounted. The housing is 
adapted to be placed within the resonating chamber body of the guitar, and 
includes a mounting portion adapted to mate with a clip which is affixed 
to the inside of the guitar proximate the sound hole. The housing is 
further provided with gripping means to permit it to be supported by the 
hand of the installer to allow the transmitter to be manually manipulated 
about the guitar strings and through the sound hole for affixation to the 
clip. In a preferred embodiment, the gripping means may comprise a stopped 
bore extending into the interior of the housing from an exterior end face 
thereof, the bore being dimensioned to allow the unit to be supported upon 
a finger of the user. 
In an alternative embodiment, the transmitter is mounted in an elongated 
housing. A frictional mount member is rotatably mounted to one end of the 
housing, the transmitter microphone being pivotally mounted to the other 
end of the housing. This embodiment is especially well adapted for 
frictional engagement with instruments having F-shape sound holes.

DETAILED DESCRIPTION OF THE INVENTION 
Referring initially to FIGS. 1 through 3, in a first embodiment of the 
invention, the transmitter 10 unit is configured to be mountable to a 
guitar 12. To provide optimized pickup and response to the generated 
sounds, the transmitter is removably placed within the guitar body through 
the sound hole 14. As seen in FIG. 2, the transmitter 10 may be fashioned 
with a main housing portion 16 having a cylindrical extension 18 
projecting from its rear face. A microphone 20 and an on/off switch 22 may 
be mounted upon the front face 24, which is contoured to be concentric 
with the sound hole 14 when mounted to the guitar. An indicator, such as 
an LED, as well as a microphone gain control (not shown) may also be 
located on the face. By the use of appropriate miniaturized components, 
such as surface mount technology integrated circuits, a high fidelity r.f. 
transmitter assembly and power source, such as mercury batteries, may be 
installed and mounted within the housing. 
The cylindrical projection portion 18 may be terminated by a threaded cap 
26 which can be removed to provide access to a battery chamber within the 
cylindrical projection portion 18. By the use of an appropriately chosen 
transmission frequency, the required antenna (not shown) may be of minimum 
length, and may be fabricated within the housing, especially if the 
housing is of a nonconductive material, such as plastic. Alternatively, it 
may be possible for the antenna, typically in the form of a thin wire, to 
project outwardly from the housing. 
In a first form of mounting, a mounting clip 28 is provided. The clip 
includes a plate 30 having an adhesive surface 32 which allows the clip to 
be adhesively affixed to the inner surface 34 of the guitar top wall 36, 
as shown in FIG. 3. Mounted to the plate 30 is the clip portion 38, 
configured to frictionally engage the cylindrical projection portion 18 of 
the transmitter unit 10. The mounting plate is positioned on the guitar 
front wall such that the curved front face 24 of the transmitter will be 
concentric with a portion of the sound hole edge when installed upon the 
bracket, recessed slightly from the edge to maximize the unobtrusiveness 
of the transmitter. 
In order to facilitate mounting of the transmitter upon the bracket, a 
cylindrically walled recess 40 extending inwardly into the housing is 
provided on the front wall 24 of the transmitter. The bore is dimensioned 
to accept a finger, and preferably the 5th finger, whereby the transmitter 
can be supported thereon. So placed, the transmitter may be manipulated 
through the sound hole 14 and snapped into engagement with the mounting 
clip 28 by engaging the cylindrical projection 18 with the clip 38. The 
transmitter may similarly be removed from the clip by inserting the finger 
into the bore and pivoting the projection 18 out of contact with the clip. 
In order to provide an alternative means for mounting the transmitter, a 
second clip 42 may be provided, as shown in FIG. 2. This clip, which 
allows mounting to the sound hole without permanent affixation of a clip 
thereto, is generally U-shaped, the first leg of the U being a cylindrical 
portion 44, adapted and dimensioned to be insertable in a frictional fit 
within the bore 40 of the transmitter. The second leg 46 of the U is 
adapted to engage with the top surface of the guitar top wall 36, and may 
be provided with a downwardly-directed terminating lip 48. The spacing 
between the legs is such that, with the clip cylindrical portion 44 
inserted into the bore 40, the top surface of the housing 16 and the 
second clip leg 46 frictionally engaging the embraced guitar top wall, as 
seen in FIG. 3A. The clip may preferably be formed of a resilient 
material, such as clear plastic, to permit flexure of the second leg 46 
and to allow a snug fit to be developed between the cylindrical portion 44 
and the transmitter housing bore 40. While this clip provides a small 
amount of exposed surface, the choice of a clear plastic for its 
construction makes the clip virtually invisible. Such a construction may 
be preferable in circumstances where the user does not wish to permanently 
(or semi-permanently) affix the adhesively mounted clip 28 to the guitar. 
Again, the transmitter is preferably positioned on the clip portion 44 
such that it is slightly recessed from the sound hole edge. 
FIGS. 4 through 6 depict an alternative embodiment for the invention which 
also may be utilized in connection with a guitar or similar instrument 
having a round sound hole 14. As depicted therein, the transmitter 10 may 
be formed with parallel top and bottom surfaces, its curved front face 24 
having the microphone 20 and finger bore 40. The switch 22 is provided on 
side wall 50. In this embodiment, the top and bottom surfaces of the 
housing are provided with opposed, parallel grooves 52, 54 extending 
between the housing's front and rear faces. 
Mounting clip 56 is provided with a first U-shaped clip portion 70 having 
legs 58, 60 spaced to accommodate the height of the transmitter 10, and 
having opposed, inwardly-directed ridges 62, 64 to engage the respective 
grooves 52 and 54 in the top and bottom walls of the housing and thus 
provide a positive engagement between the clip and transmitter. To permit 
the mounting clip to be mounted to the guitar, a second U-shape clamp 
portion 66, is formed integral with the base 68 of the arm assembly, its 
leg 72 and base defining an upwardly-directed mouth. This clamp portion is 
adapted and dimensioned to engage with an internal transverse rib 74 of 
the guitar, best seen in FIG. 6, which is normally positioned on the lower 
surface of the guitar top wall 36 proximate the sound hole 14. With the 
clip 56 mounted to the rib 74, the transmitter, placed on the finger of 
the user by utilization of bore 40, may be inserted into place on the clip 
through the sound hole. The transmitter 10 may be similarly removed when 
desired, the clip 56 remaining in place. 
An alternative embodiment of the invention may be utilized in connection 
with instruments having F holes, such as celli, double basses and the 
like, as opposed to the round holes of guitars. As depicted in FIGS. 7 
through 9, the transmitter 10 of this embodiment is in the form of an 
elongated, preferably cylindrical, housing 76 in which is located the 
transmitter circuitry and power supply. An on/off switch and power 
indicator, such as an LED (not shown) may be mounted upon the housing 
sidewall, which may consist of two threadably interconnected portions to 
provide access to the housing interior for battery replacement and the 
like. The antenna may be positioned within the housing parallel to the 
length of the housing or may be in the form of an external wire as 
previously discussed. Affixed to a first end of the housing, through 
pivoting joint 78, is microphone 80. A second pivot joint 82 assembly is 
located at the opposite end of the housing, and supports resilient 
mounting puck 84. The puck 84 may be formed in two independent portions. 
The first portion 86 is of cylindrical construction, having a center 
aperture allowing it to be frictionally mounted upon the shaft 88 of the 
pivot joint assembly. The outer diameter of the portion is chosen to 
provide a tight frictional fit with the sides of the lower, wider portion 
90 of the instrument's F hole 92. The second or head portion 94 is 
provided with a threaded central aperture adapted to mate with a threaded 
shank 96 extending from the end of the pivot joint assembly shaft 88. The 
diameter of the head is typically greater than that of the first portion, 
and is chosen to provide an acceptable grip for the puck while not being 
overly intrusive to the appearance of the instrument. The head also 
assists in retaining the first puck portion on the shaft. Rotation of the 
puck allows the orientation of the transmitter 10 to be adjusted as 
desired. Preferably, the transmitter is to be oriented to lie parallel to 
the instrument's top wall, hanging downwardly when the instrument is in 
the upright position, as depicted in FIG. 8. 
Because of the compact design of the embodiment of FIGS. 7 through 9, it 
may be used in connection with other instruments, not having F holes, as 
well as in other locations on instruments. As shown in FIG. 10, the clip 
38 as detailed in FIG. 2 may be utilized to engage the cylindrical body of 
the transmitter for mounting within the body of an instrument, such as a 
guitar, the clip being affixed to an interior surface, such as the inner 
surface 34 of the guitar top wall 36. 
Alternatively, and as depicted in FIGS. 11 and 12, the transmitter may be 
inserted between the lower end of an instrument fingerboard 98 and the top 
of the instrument sound box 100. Certain string instruments, such as 
celli, mount the fingerboard to the instrument only at its upper, neck 
end, the lower distal end remaining free of the fingerboard, producing a 
gently tapering space therebetween extending along the neck of the 
instrument. As shown in FIG. 12, when so utilized, the puck 84 and head 94 
are chosen to be of the same diameter such diameter allowing for a 
frictional fit between the fingerboard and sound box. So mounted, the 
transmitter is again virtually hidden from view, the resilient mounting of 
the transmitter insignificantly modifying the tonal characteristics or 
response of the instrument. 
Receivers and amplifiers as known in the art may be utilized in conjunction 
with the invention. Because of the superior fidelity and response of the 
present invention, the receiver may be preferably provided with a 
switching mechanism to avoid the creation, amplification and reproduction 
of switching transients which can normally occur as the transmitter and 
receiver/amplifier are energized. As shown in the FIG. 13, the 
receiver/amplifier is provided with a main power supply 102 which is 
connected to the operative stages of the receiver/amplifier through main 
power switch 104. The amplifier stages are isolated, however, from the 
receiver stage 106, by switch 108, which is typically a semiconductor 
switch operable by a control signal provided to an appropriate input 
terminal. The switch 108 is utilized to isolate the amplifier 110 from the 
receiver output to prevent noise spikes and the like generated during 
transmitter energization from being passed to the speakers. 
A carrier detector 114 is coupled to the receiver 106 and is adapted to 
provide an output when the radio-frequency carrier of the transmitter is 
received. This output is passed to delay circuit 116, which in turn 
provides an output only after it has received an input signal for a 
predetermined length of time, typically 1 to 2 seconds. After such delay, 
the delay line output is used to activate switch 108, which then passes 
the audio output from receiver 106 to the following amplification 
circuitry. The delay is chosen to prevent the transmission, typically 
occurring immediately after transmitter turn-on, from being received, 
amplified and reproduced as pops, squeaks or other annoying sounds. 
As presented herein, the transmitter of the present invention provides high 
clarity, distortion and interference-free reproduction of the sounds of a 
musical instrument when it is used, without defacement of or intrusion 
upon the aesthetic sensibilities of the player and audience. The 
microphone of the transmitter, being located within or in close proximity 
to the sound box, is capable of receiving the full spectrum of fundamental 
harmonic frequencies produced by the instrument, thus providing for full 
and faithful transmission of the music.