GB2235562A

GB2235562A - Pick-ups for stringed electrical musical instruments

Info

Publication number: GB2235562A
Application number: GB8917388A
Authority: GB
Inventors: Andrew James Rothwell
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-07-29
Filing date: 1989-07-29
Publication date: 1991-03-06
Also published as: GB8917388D0

Abstract

A pick-up 1 for an electric guitar comprises first and second pick-up coils L1, L2 connected in series, and a circuit 2 of variable impedance which contains at least one inductive and/or capacitive element and is connected in parallel with the first pick-up coil L1. The user of the pick-up may selectively vary the impedance of the circuit 2 between a first setting in which the impedance is effectively a high impedance for all frequencies, and a second setting in which the impedance effectively varies between the bass and treble frequencies. The specification also discloses a pick-up arrangement in which first and second pick-up coils are situated in such a manner as to cause cancelling out of noise in a resultant signal from the pick-up coils. <IMAGE>

Description

PICK-UPS FOR STRINGED ELECTRICAL MUSICAL INSTRUMENTS This invention relates to pick-ups for stringed electrical musical instruments, and is concerned particularly although not exclusively with pickup for electric guitars.

An electric guitar pick-up typically comprises a plurality of pole pieces, each associated with one of the strings of the guitar, and a coil wound about the pole pieces. As is well known, vibrations in the guitar strings cause corresponding variations in the magnetic field in the vicinity of the respective pole piece. Such magnetic field variations induce a corresponding electric current in the pick-up coil, to constitute a signal which is subsequently processed and amplified to reproduce the sound.

Certain types of electric guitar pick-up have a single coil, which characteristically gives a bright, clear sound. Other types of guitar pick-up comprise double coils, which characteristically give a rich, warm sound. The double coils of such pick-ups are often wound in opposing senses, and/or are associated with pole pieces of opposite plurality, so as to reduce the effects of background noise, and are consequently often referred to as "humbucking" pick-ups.

Single coil pick-ups are often criticized for having a rather thin sounding bass response, whilst humbucking pick-ups are often criticized for having a rather dull treble response.

Preferred embodiments of the present invention aim to provide guitar pick-ups which may be improved in the foregoing respects.

More generally, according to a first aspect of the present invention, there is provided a pick-up arrangement for a stringed electrical musical instrument, the pick-up arrangement comprising first and second pickup coils connected in series, and a circuit of variable impedance which contains at least one inductive and/or capacitive element and is connected in parallel with the first pick-up coil such that a user of the pick-up may selectively vary the impedance of said circuit between a first setting in which said impedance is effectively a high impedance for all frequencies of the stringed instrument and a second setting in which said impedance effectively varies between the bass and treble frequencies of the stringed instrument.

Preferably, in said second setting, said impedance is high at bass frequencies and low at treble frequencies of the stringed instrument.

Preferably, the arrangement is such that a user may vary said impedance to a third setting in which said impedance is effectively a low impedance for all frequencies of the stringed instrument.

Said circuit preferably comprises at least one capacitor and/or at least one variable resistor.

Preferably, said circuit comprises at least one switch by means of which the effective impedance of the circuit may be varied. The circuit may comprise a capacitor and a variable resistor in parallel combination and, in series with that combination, a switch.

In a particularly preferred configuration, said circuit comprises two sub-circuits connected in series with one another, one of the sub-circuits comprising a variable resistor connected in parallel with the series combination of a first capacitor and a first switch, and the other of the sub-circuits comprising a second capacitor connected in parallel with the second switch.

Preferably, said first and second switches are arranged to be opened and closed together.

At least one of said first and second coils may be the coil of a respective single-coil pick-up or one coil of a respective twin-coil humbucking pick-up.

Said first and second coils may be respective coils of a common twin-coil humbucking pick-up.

In a second aspect, the invention provides a pick-up arrangement for a stringed musical instrument, the pick-up arrangement comprising first and second pickup coils connected in such a manner as to cause cancelling out of noise in a resultant signal from said pick-ups, the pick-ups being mounted one above the other so that they may be mounted together at substantially the same position, longitudinally of the strings of a stringed instrument.

Preferably, such a pick-up arrangement comprises a first set of first and second pick-up coils as aforesaid and a second set of first and second pick-up coils as aforesaid, the first and second sets being interconnected to provide a resultant signal therefrom and being so arranged that they may be mounted at spaced locations, longitudinally of the strings of a stringed instrument.

Preferably, said first and second sets are so interconnected as to cause cancelling out of noise in a resultant signal from them.

A pick-up arrangement in accordance with the second aspect of the invention may also be in accordance with the first aspect of the invention.

The invention extends to a stringed electrical musical instrument provided with a pick-up arrangement embodying the first and/or second aspect of the invention. Such a musical instrument may comprise a guitar.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings, in which: Figure 1 is a circuit diagram of a guitar pick-up embodying the invention; Figure 2 shows one example of a circuit used in the pick-up of Figure 1; Figure 3 shows an alternative circuit for use in the pick-up of Figure 1; Figures 4(a) to (d) show yet further alternative circuits for use in the pick-up of Figure 1; Figure 5 is a circuit diagram of a pick-up arrangement similar to that of Figure 1, but comprising two humbucking pick-ups arranged in series; Figure 6 shows a variation of the circuit diagram of Figure 5; Figure 7 illustrates a physical realisation of part of a novel pick-up which may be used in the arrangement of Figure 5 or 6;; Figure 8 shows a variation of the novel pick-up of Figure 7; Figure 9 illustrates part of a complete twin pick-up of the type illustrated in Figure 8; and Figure 10 illustrates a variation of the complete twin pick-up of Figure 9.

The pickup 1 that is illustrated in Figure 1 is a twin coil humbucking pick-up, comprising a first pickup coil L1 and a second pick-up coil L2, which are connected in series. In use, an electrical signal appears across terminals A and B, and is subsequently processed and amplified to provide the electric guitar sound. In an alternative arrangement, each of the pickup coils L1, L2 may be the coil of a respective, separate, single-coil pick-up.

A variable impedance circuit 2 is connected to terminals X and Y, so as to be connected in parallel with the first pick-up coil L1.

A first example of the variable impedance circuit 2 is shown in Figure 2. It comprises two sub-circuits connected in series. The first sub-circuit comprises a variable resistor RV1 which is connected in parallel with the series combination of a first switch SWla and a first capacitor C1. The second sub-circuit comprises a second capacitor C2 which is connected in parallel with a second switch SWlb. The two switches SWla and SWlb are provided as respective poles of a double-pole single-throw switch.

when the switches SWla and SWlb are open, then the series combination of variable resistor RV1 and capacitor C2 is placed in parallel with the pick-up coil L1. When the variable resistor RV1 is set to maximum resistance, the impedance presented by the circuit 2 is so high that the circuit may be practically ignored. The pick-up 1 then behaves just like a normal humbucking pick-up, with the two coils L1 and L2 connected in series across the output terminals A and B. However, when the variable resistance RV1 is set to minimum resistance, the capacitor C2 is effectively placed in parallel with the coil L1. Since the capacitor C2 will have a low impedance at high frequencies and a high impedance at low frequencies, this causes the pick-up 1 to act like a conventional humbucking pick-up for low frequencies, but like a single coil pick-up for high frequencies. Thus, one may obtain the treble clarity of a single coil pickup, whilst preserving the rich, warm bass tones of a humbucking pick-up. By varying the setting of the variable resistor RV1, the effect may be modified to suit the player's taste.

When the switches SWla and SWlb are closed, the capacitor C2 is shorted out, and the parallel RC circuit comprising the variable resistor RV1 and the capacitor C1 is placed in parallel with the first coil L1.

With the variable resistance RV1 set to minimum resistance, both the capacitor C1 and the coil L1 are effectively shorted out, so that the humbucking pick-up 1 is transformed into what is effectively a single coil pick-up, with only the second pick-up coil L2 generating significant signals. When the variable resistance RV1 is set to maximum resistance, the first capacitor C1 is effectively placed in parallel with the first pick-up coil L1.

This would appear to be the same situation as with the switches SWla and SWlb open and the variable resistor RV1 set to minimum, but by choosing different values for the capacitors C1 and C2, a different effect is achieved and, of course, the effects are continuously variable by varying the setting of variable resistance RV1.

Thus, depending upon the position of the switch SW1 and the setting of the vari-able resistor RV1, the response of the pick-up 1 may be varied between a fully humbucking sound, a single coil sound, and a "combination" sound having the favourable bass characteristics of a humbucker and the favourable treble characteristics of a single coil.

The values of the circuit components will depend upon the impedance of the pick-up coils L1, L2, and will also be, to some degree, a matter of musical taste.

However, purely by way of example, a prototype was constructed and tested having the following values: DC resistance of coils L1, L2 = 4,500(-) RV1 = 220kill log C1 = 3.3nF C2 = 22nF.

With circuit components of the above values, the pick-up arrangement was found to work particularly well.

Conveniently, the components RV1, SWla and SWlb may be incorporated in a single potentiometer with combined push/pull switch.

The variable impedance circuit 2 of Figure 1 may have various different configurations. For example, in the simplified configuration shown in Figure 3, only the components RV1 and C1 of Figure 2 are used to form a single RC parallel network, in series with a single switch SW1, between the terminals X and Y.

Further variations of the variable impedance circuit 2 of Figure 1 are shown in Figures 4(a) to 4(d).

In Figure 4(a), the circuit 2 comprises a capacitor included in series with a variable resistance and a switch. In each of Figures 4(b) to 4(d), a parallel circuit is connected in series with a single switch. In Figure 4(b), the parallel circuit comprises a first variable resistance in parallel with the series combination of a second variable resistance and a capacitor. In Figure 4(c), a first variable resistance is connected in parallel with a first capacitor and a series combination of a second variable resistance and second capacitor. In Figure 4(d), a first capacitor is connected in parallel with the series combination of a variable resistance and a second capacitor.

It will be appreciated that various different tonal effects will be achieved by use of the various circuits illustrated in Figures 2 to 4, and by choice of different values for the circuit components.

As mentioned above, the pick-up arrangement 1 of Figure 1 may be modified to provide two separate single coil pick-ups, each of which includes a respective one of the two coils L1 and L2. In a further variation, as shown in Figure 5, each of the coils L1 and L2 may be contained in a respective, separate, humbucking pick-up.

Thus, in Figure 5, the coil L1 comprises two sub-coils Lla and Llb connected in parallel to form a first humbucking pick-up. Similarly, the second coil L2 comprises two sub-coils L2a and L2b which are connected in parallel, to form a second humbucking pick-up, which is connected in series with the first humbucking pick-up across the output terminals A and B. In the example of Figure 5, the variable impedance circuit 2 is of the configuration shown in Figure 3.

The variation of Figure 6 is generally similar to that of Figure 5, except that, for each of the separate humbucking pick-ups, the two sub-coils Lla-Llb and L2a L2b are connected in series rather than parallel.

The arrangements illustrated in Figures 5 and 6 may be further improved by the adoption of a novel pickup arrangement, some examples of which are illustrated in Figures 7 to 10.

In Figure 7, the two pick-up coils Lla and Llb of, for example, the circuit of Figure 5 or 6, are placed one on top of the other, with a ferromagnetic plate 3 between them. There are six individual pole pieces 4a, 4b for each of the coils Lla, Llb. As may be seen in Figure 7, the South poles of the pole pieces 4a, 4b are disposed adjacent one another, but the ferromagnetic plate 3 prevents the magnets from repelling one another.

The two coils Lla, Llb may be wired in parallel (asian Figure 5) or in series (as in Figure 6). As long as they are wired out of phase, the combination of the two coils, which together form the coil L1, serves as a noise-cancelling unit.

The two coils L2a, L2b of Figure 5 or 6 may be constructed in an equivalent manner, to form the coil L2 as another noise-cancelling unit. If the two coil units L1 and L2 are then place side by side and wired in series and out of phase, as. illustrated in Figure 5 or 6, then the resulting pick-up arrangement would look and sound like a normal humbucking pickup, but each of the two coil units L1 and L2 would in fact be a selfcontained noise - cancelling unit in itself.

In fact, each unit L1 and L2 would in itself be more effective in cancelling noise without losing high frequency harmonics. This is because, in a normal humbucking pickup, the longitudinal spacing between each coil (e.g about 2 cm) is sufficient to cause phase cancellation between harmonics whose wavelength is of the order of twice the longitudinal spacing (e.g. about 4 cm).

By adopting the construction of Figure 7, if the coil L1 (Figure 5 or 6) is completely shorted out (e.g.

if the circuit 2 were to be replaced by a simple switch), then coil L2 still serves as an effective noise cancelling unit, with full high frequency response. If the full circuit 2 of Figure 5 or 6 is used (optionally as modified in Figure 4), then the aforementioned tone variations will be possible, without compromising the noise cancelling properties of the pickup arrangement.

Figure 8 shows an alternative arrangement to Figure 7. The six individual magnets of the top coil Lla of Figure 7 have been replaced by a single bar magnet having its North pole on an upper surface 5 and its South pole on a lower surface 6. Since the lower coil Llb is to a large extent shielded from the strings by the ferromagnetic plate 3, it will pick up only a weak signal. Therefore, in an alternative arrangement, the lower coil Llb is wound simply around a non-ferromagnetic former 7. The coil Llb will still serve to cancel noise, but will be largely unaffected by the vibrating strings.

Figure 9 shows a complete magnetic assembly for the coils L1 and L2, constructed in accordance with the example of Figure 8, but in which the actual coil windings Lla, Llb and L2a, L2b are omitted, in the interests of clarity. Thus, the coil Lla is wound about a first permanent magnet A, having its North pole as upper surface 5, whilst the coil L2a is wound about a second permanent magnet C, having its South pole as upper surface 5. The coils Llb and L2b are wound about the non-ferromagnetic formers B and D respectively. The ferromagnetic plate 3 is common to both coils L1 and L2.

In the variation of Figure 10, a single permanent magnet 8 is placed between and in contact with two ferromagnetic bars 9, which serve as pole pieces for the coils Lla and L2a respectively. The coils Llb and L2b are again wound about non-ferromagnetic formers B and D, disposed below the common ferromagnetic plate 3.

In the above circuit examples, where two variable resistors are used, these may conveniently be provided by a dual-ganged potentiometer which is wired either so that both resistances increase together, or so that as one resistance increases, the other decreases.

Alternatively, separate potentiometers may be provided.

As a rough guide, where a single capacitor is provided in the variable impedance circuit 2 then, if the d.c.

resistance of the pick-up coils is Rrl, the value C/uF of the capacitor may be chosen so that the product RC 15 approximately.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A pick-up arrangement for a stringed electrical musical instrument, the pick-up arrangement comprising first and second pick-up coils connected in series, and a circuit of variable impedance which contains at least one inductive and/or capacitive element and is connected in parallel with the first pick-up coil such that a user of the pick-up arrangement may selectively vary the impedance of said circuit between a first setting in which said impedance is effectively a high impedance for all frequencies of the stringed instrument and a second setting in which said impedance effectively varies between the bass and treble frequencies of the stringed instrument.

2. A pick-up arrangement according to claim 1, wherein, in said second setting, said impedance is high at bass frequencies and low at treble frequencies of the stringed instrument.

3. A pick-up arrangement according to claim 1 or 2, wherein the arrangement is such that a user may vary said impedance to a third setting in which said impedance is effectively a low impedance for all frequencies of the stringed instrument.

4. A pick-up arrangement according to any of claims 1 to 3, wherein said circuit comprises at least one capacitor.

5. A pick-up arrangement according to any of claims 1 to 4, wherein said circuit comprises at least one variable resistor.

6. A pick-up arrangement according to any of the preceding claims, wherein said circuit comprises at least one switch by means of which the effective impedance of the circuit may be varied.

7. A pick-up arrangement according to claim 6, wherein said circuit comprises a capacitor and a variable resistor in parallel combination and, in series with that combination, a switch.

8. A pick-up arrangement according to claim 6, wherein said circuit comprises two sub-circuits connected in series with one another, one of the sub-circuits comprising a variable resistor connected in parallel with the series combination of a first capacitor and a first switch, and the other of the sub-circuits comprising a second capacitor connected in parallel with a second switch.

9. A pick-up arrangement according to claim 8, wherein said first and second switches are arranged to be opened and closed together.

10. A pick-up arrangement according to any of the preceding claims, wherein said first and second coils are the coil of a respective single-coil pick-up or one coil of a respective twin-coil humbucking pick-up.

11. A pick-up arrangement according to any of claims 1 to 10, wherein said first and second coils are respective coils of a common twin-coil humbucking pick-up.

12. A pick-up arrangement for a stringed musical instrument, the pick-up arrangement comprising first and second pick-up coils connected in such a manner as to cause cancelling out of noise in a resultant signal from said pick-up coils, the pick-up coils being mounted one above the other so that they may be mounted together at substantially the same position, longitudinally of the strings of a stringed instrument.

13. A pick-up arrangement according to ' claim 12, comprising a first set of first and second pick-up coils as aforesaid and a second set of first and second pick-up coils as aforesaid, the first and second sets being interconnected to provide a resultant signal therefrom and being so arranged that they may be mounted at spaced locations, longitudinally of the strings of a stringed instrument.

14. A pick-up arrangement according to claim 13, wherein said first and second sets are so interconnected as to cause cancelling out of noise in a resultant signal from them.

15. A pick-up arrangement according to any of claims 1 to 11 and according to any of claims 12 to 14.

16. A pick-up arrangement substantially as hereinbefore described with reference to the accompanying drawings.

17. A stringed electrical musical instrument provided with a pick-up arrangement according to any of the preceding claims.

18. A musical instrument according to claim 17, being a guitar.