This invention relates to passive electromagnetic pickup devises for stringed musical instruments with at least one metal string made by magnetic permeable material. Such musical instruments are the electric or acoustic guitars, violin, or any other stringed musical instrument with strings. In the particular embodiment the device invented produces a high quality audio electric signal with no noise caused by the surrounding space electromagnetic fields.
One common method for amplifying the sound of a stringed musical instrument having one or more metal strings made by magnetic permeable material uses a magnetic pickup assembly positioned beneath the strings of the musical instrument. Such a magnetic pickup includes one or more signal picking coils wrapped around one or more magnetic permeable metal cores which are themselves magnetic, or which are magnetized by an adjacent permanent magnet. The magnetic field created by this permanent magnet structure does not generate an electric signal inside of the signal picking coil by itself, because the magnetic field flow, flowing through the turns of the signal picking coil, is a constant. As a result of the position of the strings near the magnet structure of the magnetic pickup, a small string area becomes magnetized. This magnetized string area has a size close to the width of the permanent magnet means exposed from the top side of the pickup. The small, magnetized string area radiates its own flow of magnetic field fluxes with an expanded pattern toward the signal picking coil. The flow of magnetic field fluxes passes through the turns of the signal picking coil. When the string does not vibrate this magnetic flow does not create an electric signal inside the signal picking coil. Picking or strumming a string causes the string to vibrate mechanically and the small, magnetized string area vibrates too. This causes an alternative magnetic field flow to pass through the turns of the signal picking coil, which generates an alternative audio electric signal that corresponds to the frequency of the string mechanical vibration. That audio electrical signal measured between the start and end terminals of the signal picking coil are available for further electronic amplification. Based on that conception theory it was found that the only magnetic pickup capable of reproducing the mechanical vibration of a string with maximum accuracy, is the single coil style magnetic pickup. There is one major undesirable disadvantage of the single coil style magnetic pickup—it picks the electromagnetic noise from the surrounding space, where the magnetic pickup is exposed. Electromagnetic noises in the space are generally produced and radiated by power transformers, power diode rectifiers, electric motors etc.
There are a few conventional methods, which use dual coil magnetic pickup assemblies to cancel that undesirable electromagnetic noise. One of these methods is called classic humbucking pickup, which includes two side-by-side positioned identical coils permanently or switchably connected in series or in parallel. Another popular method uses two stacked (one on the top of the other) identical single coil windings permanently or switchable connected in series or in parallel. These two most popular methods, generally cancel the undesirable noise but they also change the musical specter of the generated audio electric signal in one or another way. The frequency response, the phase and harmonic content of the generated audio electric signal are changed too.
It is a first object and advantage of this invention to keep the tonal clarity and frequency response of the single coil style magnetic pickup when it is sensing the mechanical musical string vibrations of the musical instrument.
It is a further object and advantage of this invention to provide an effective noise cancellation of the electric noise signals generated by the surrounding alternative magnetic fields.
It is an other object and advantage of this invention that a single large noise picking coil is capable of effectively canceling the noise for multiple single style signal picking coils installed on a stringed musical instrument.
The foregoing disadvantages and other problems are overcome and methods and apparatus in accordance with the embodiment of this invention realize the objects and advantages. A Magnetic pickup device for a stringed musical instrument with large free shape low impedance coil for noise cancellation generates an output audio electric signal, that strongly corresponds to the frequency, phase and harmonic content of the string mechanical musical vibrations. Also, the electric noise components contained in the generated audio electric signal are effectively cancelled.
Referring to
In general:
A large free shape low impedance coil for noise cancellation is a coil winding, that has these shapes and overall geometrical dimensions which provide a square surface area of 5 (five) or more times larger than the average square surface area of a regular single coil style signal picking coil. This requirement provides a high efficiency for electromagnetic noise picking and a low impedance (ohm resistance and reactive inductance) of the large free shape low impedance coil for noise cancellation. It is theoretically and experimentally proven that there is a ratio between the units (as a number) squares surface area and the units (as a number) linear length of any single turn that is part of a multiple turns coil. This ratio determines the capability of one unit linear length of a certain coil turn to produce a certain amount units square surface area. For small size and slotted shape (the length of the turn is significantly bigger than its width) coil turn this ratio is less than 1 (one)—practically about 0.4 to 0.8. That means: 1 (one) unit linear length is capable of producing 0.4 to 0.8 units square surface area. Increasing the geometrical size of the coil turn and making the coil shape closer to a circular shape makes this ratio bigger and bigger—practically up to 10 times. This ratio is important when a high efficiency for capturing of electromagnetic noise from the surrounding space and a low impedance (ohm resistance and reactive inductance) of the coil are desired. The large circular shape coil drawn on
The present invention can be used with any stringed musical instrument for which an electrical amplification is need.
One preferred embodiment of the invention is particularly adapted for use with electric guitar with six strings made by magnetic permeable metal. According to
The electric guitar shown on
The strings (10) are hooked at their first end (as shown on
The magnetic field, created by the permanent magnet rods inserted into the signal picking coil (4), by itself, does not generate any signal inside the signal picking coil (4), because that flow of magnetic field passing through the signal picking coil turns is constant. As a result of the close position of the string next to the permanent magnet rods, a small string area is magnetized. This magnetized, string area is with a size close to the diameter of the magnetized rods exposed. The small, magnetized string area radiates its own flow of magnetic field fluxes with an expanded pattern toward the signal picking coil (4). When the string does not vibrate this magnetic flow does not create an electric signal inside the signal picking coil. Picking or strumming a string causes the string to vibrate mechanically and the small magnetized string area vibrates too. This causes an alternative magnetic field flow to pass through the turns of the signal picking coil (4), which generates an alternative audio electric signal that corresponds to the frequency of the string mechanical vibration. An audio electric signal can be measured between the start (5) and end (6) terminals of the signal picking coil (4). At the same time the signal picking coil (4) is exposed to all noise electromagnetic fields emitted in the surrounding space. As a result, a noise electric signal is created inside the signal picking coil (4) along with the audio electric signal created by the string vibrations. The large noise picking coil (7) is exposed to the same noise components as the signal picking coil (4). Thus, a noise electric signal with the same amplitude and frequency is created inside the large noise picking coil (7). At the same time the large noise picking coil (7) practically does not respond to the string vibrations because of its large size and low number of turns contained. Connecting the signal picking coil (4) with the large noise picking coil (7) in series, results in a total cancellation of the two noise electric signals (which are identical in amplitude and opposite in phase), while the audio electric signal created mostly by the signal picking coil (4), stays not affected and with a strong amplitude. A final output audio electric signal with no noise components is being produced for further electronic amplification.
For additional noise reduction, both the signal picking coil (4) and the large noise picking coil (7) are shielded. The large noise picking coil (7) is shielded with the Shield of the large noise picking coil (7a), which is made by fine thickness copper or aluminum foil or other shielding technique. For protection against undesirable microphonic effect, both the signal picking coil (4) and the large noise picking coil (7) are wax or lacquer potted. Also the large noise picking coil (7) is finally firmly attached (glued) to the musical instrument body (1).
A basic electric schematic of the invention, shown on
The basic electric schematic on
The above description disclosed and the drawings attached, clearly describe the Magnetic pickup device for a stringed musical instrument with large free shape low impedance coil for noise cancellation. While the invention was particularly shown and described with respect to preferred embodiment thereof, it will be understood by those skilled in the art that changes in form and details may be made therein without departing from the scope and spirit of the invention. Therefore, this invention is not to be limited by the disclosure and the drawings, but by the claims listed.
This patent application is a continuation of the Provisional Patent application Ser. No. 60/521,231 filed on Mar. 16, 2004 by Ilitch Chiliachki.
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