GB2155230A

GB2155230A - Electric stringed instrument

Info

Publication number: GB2155230A
Application number: GB08502753A
Authority: GB
Inventors: Andrew Bond
Original assignee: BOND GUITARS Ltd
Current assignee: BOND GUITARS Ltd
Priority date: 1984-02-02
Filing date: 1985-02-04
Publication date: 1985-09-18
Also published as: GB8502753D0

Abstract

An electric stringed instrument e.g. a guitar, has active electronic signal processing circuitry on board the instrument. Signals from pick-ups 41, 42, 43 are supplied to an array of analogue phase inverters 67, 68 and selectively mixed and processed further at 69, 70, 74, 78 to give the instrument a particular desired sound. Electronic tuning means is also provided and an LED display is used to indicate the state of tuning of the strings. <IMAGE>

Description

SPECIFICATION Electric stringed instrument This invention relates to an electric stringed instrument, in particular a guitar, which is provided with circuitry in the body of the instrument to allow the musician playing the instrument a greater degree of control of the types of sound produced and/or to facilitate the tuning of the instrument.

In the past electric stringed instruments, such as electric guitars, have been made with one or more pick-ups arranged underneath the strings, in the rigid body portion of the instrument. When the instrument is played, the signals picked up by the pick-up(s) are fed via a lead to an amplifier and/or various other signal processing circuitry.

In the instrument of the present invention, to alter the sound of the instrument, the signals from the pick-ups may be processed by active electronic circuitry "on board" the instrument to give the desired effect.

In accordance with the present invention, there is provided a stringed musical instrument having a body portion, at least one pick-up and, incorporated in the body portion, active electronic circuitry for processing the output of the pick-up(s) and/or for assisting in tuning the strings of the instrument.

In preferred embodiments of this invention, the guitar is provided with "on board" or phantom power supply circuitry for supplying the appropriate power line voltages to the electronic circuitry.

The type of electronic signal processing circuitry envisaged for inclusion in the instrument of this invention includes such devices as phase-changers, means for electronically combining the outputs of a number of pick-ups, means for producing attacksustain-decay response, amplifiers, tuning means, memory circuitry, etc, all of which may be under the direct control of the musician from a keyboard or switches on the instrument.

An example of a stringed instrument suitable for use with the electronic processing circuitry of the present invention has been described in our earlier British Patent Application No 84 02837, the disclosure of which is incorporated herein by way of reference. In that application, we describe an electric guitar having a body portion, a neck and a head stock comprising a structural foam plastics material integrally moulded about a reinforcing member of fibre reinforced plastics material, said reinforcing member extending into said head stock and said body portion for at least the full length of the strings to provide a rigid beam support for said strings, a recess being provided in the part of the reinforcing member in said body portion, pick-ups being provided in said recess to sense vibration of the strings through at least one aperture in the front of the guitar body portion.

The invention will be further described, by way of example, with reference to the accompanying drawings: Figure 1 is a top view of a guitar embodying the invention; Figure 2 is a side view of the guitar of Figure 1 with the strings removed; Figure 3 is a longitudinal section of the body of the guitar with the neck and working parts removed; Figure 4 is across-section of the body of the guitar of Figure 3; Figure 5 is a fragmentary rear view of the body of the guitar with the back panel removed and with details of the electronic circuitry mounted in the body removed; Figure 6 is a block diagram of the electronic circuitry to be included into the guitar.

Figure 7 is a block diagram of a memory circuit for use with the circuitry of Figure 6; and Figure 8 is a block diagram of a tuning display circuit for use with the circuitry of Figure 6.

Referring to the drawings, Figure 1 shows a guitar having a neck 1, a headstock 3 and a body 5.

The headstock is provided with the usual fitments including knobs 7 for controlling rotation of tuning pegs 9. The neck 1 has mounted thereon a fingerboard illustrated as a pitchboard 11 provided with ridges 12 against which the strings can be stopped during playing although this pitchboard can be replaced by a conventional fretboard if so desired.

The guitar is formed from a rigid member comprising a stressed skin 25 of fibre reinforced plastics material with which has been moulded a rigid structure of filler material 27 which conveniently may comprise epoxy resin and particulate cork.

The front 15 of the body of the guitar as illustrated in Figures 3 and 4 is comprised of moulded structural foam material. Suitably the skin 25 may be formed of boron fibre or multidirectional carbon fibre in a standard resin matrix which may, for example, be of an epoxy or a polyester resin. The structural foam material can conveniently be a structural urethane foam.

As may be appreciated from Figures 3 and 5, the rigid member extends into the headstock portion of the guitar and is formed at the other end with a frame part comprised of two spaced bifurcations 30 defining a recess therebetween with the remote ends of the bifurcations being connected by a portion 31 integral with the remainder of the beam.

The face 15 of the body 5 of the guitar is provided, as shown in Figure 1, with apertures 16, 17 and 18 for the receipt of pick-ups for sensing movement of the strings and also, as clear from Figure 1, further apertures are provided for the receipt, from below, of a binnacle 23 and switches 50 to 57. These latter apertures, for the purposes of simplification of the showing, are not illustrated in Figure 5. The rear of the body 15 is closed by a removable panel 36 as shown in Figure 3 also moulded from structural foam material similar to that of the material 27 used to cover the fibre reinforced beam. The bridge 21 is directly secured through the structural foam to the portion 31 so that the rigid member defined by the stressed skin 25 extends for the full length of the strings from the bridge to the headstock with the pegs 9 being directly supported by the rigid member.

In Figure 3 pick-ups 41, 42 and 43 and further electronic circuitry 45 (to be described below) are shown mounted on the inner surface of the rear panel 36. As shown, when the rear panel 36 is secured in its required position to the rear of the guitar body, the top ends of the pick-ups project through the apertures 16, 17 and 18 into sufficiently close proximity to the guitar strings as to be able to pick up the vibrations thereof. As shown the recess for the receipt of the pickups is thus peripherally defined by the walls 30 and 31 of the rigid member while an additional recess is provided within the body 5 of the guitar for receipt of other electronic equipment as indicated at 45.

With this arrangement, simply by removing the back panel 36, all the electronic circuitry is removed from the main body of the guitar for access for servicing or other purposes.

As can be seen in Figure 6 the individual pickups 41, 32 and 43 under control of respective on/ off switches 53, 55 and 57 (Figure 1) feed their signals into amplification and phase inverting circuitry 61. The conventional technique for achieving phase changes of 180 is by means of switches which reverse the connections to the pick-up coils. In the present embodiment the phase invertion, when required, is effected by an analogue technique where selected outputs from the pick-ups are fed to unity gain inverting amplifiers. Specifically, in the arrangement shown, each of the preamplifiers 64, 65, 66 has an output line connected to an analogue switch bank 69 and, in addition, two of the preamplifiers 64 and 66 each supply a second output signal to the switch bank 69 via respective phase inverting unity gain amplifiers 67 and 68.

Depending on the type of pick-ups used the buffering effect of the preamplifiers may not be required and outputs from the pick-ups may feed directly into the analogue switch-bank 69. Also, instead of the use of single coil pick-ups double coil pick-ups may be used. These, known as "hum bucking" pick-ups, comprise two coils which are out of phase relative to one another in order to cancel out hum.

In the embodiment shown in Figure 6 the switchbank 69 feeds output signals to mixing amplifiers 70. The way the switches in the bank are controlled is by a pick-up logic unit 71 which is in turn controlled by the person playing the guitar via switches 53 to 57 which is part of a selection keypad 72. With this arrangement the guitarist, when playing, can readily flip switches or press buttons to provide a control signal to the analogue switchbank to route through a particular combination of signals for mixing by the mixing amplifier 70 to give a particular sound.

To help the guitarist see if he has selected the correct mix of signals, an indicating device situated in the binnacle 23 which may be, for example, an LED display 23a, shows what combination of signals have been routed through to the mix amp 70.

The design of the control circuitry of the present invention also facilitates the incorporation of a memory device, such as that shown in Figure 7, which can be used to provide the pick-up logic control circuitry 71 with preset signals to produce a desired particular type of sound from the guitar.

The mix amp 70 feeds into a current controlled bass boost, treble and cut circuit which in turn is controlled by a current from the digital to analogue converter 75. This converter 75 is supplied with input signals from a four bit up down BCD counters 76, which is activated by the guitarist rom a bank of rocker switches 77 comprising the switches 50, 51 and 52. Switches 50, 51 and 52 in this case, are ramp switches which are tiltable by pressure at one end or the other from a normai level position so as to reduce or increase, as required, the volume, bass and treble equalisation. The way the count is generated is achieved by a continuous increment or decrement for the length of time the ramp switch is depressed. The circuitry may be so arranged that there is a logarithmic relationship between the counter contents and the effect of the analogue control signal derived from it.

A set of location LEDs can also be incorporated into the design of the guitar, to help the guitarist see, in difficult lighting conditions, e.g. on stages, which switches he is using. Also as a further aid to the guitarist, there may be, incorporated into the first display 23a or quite separately, a display of the degree of treble, bass, etc applied to the output from the mix amplifier.

The current controlled circuit 74 has an output, in this embodiment of the invention, which feeds to a line driver or volume tircuit 78. This driver circuit is also connected to the output of the digitalto-analogue converter 75 so that there is simultaneous control of both this circuit and the circuit 74.

The output of the circuit 78 then feeds via an output socket through an interconnecting lead 13 to a power supply unit and an audio attenuator 80 which in turn feeds the signals to the normal guitar amplifiers along leads 81.

As can be seen from the Figure the lead 13 from the power supply unit 80 also feeds power to an "on board" power supply and regulator circuit via the lines 83. This circuit 82 then supplies a regulated power supply of appropriate voltages to the digital and analogue circuitry housed in the guitar.

Figure 7 shown circuitry for enabling the settings of the signal processing circuitry to be stored and recalled.

The contents of counters 76 which control the active volume/treble/bass amplifiers can be stored in a bank of Random Access Memory chips 100 which can be put in a write mode by means of a mechanical switch 101 conveniently positioned on the instrument. An additional control keypad 102, may be used to select any one of a number of sets of data, say 16 for example, which can be stored and recalled.

In addition the state of the pick-up selection switches 69 may also be entered into RAM so once a user has found a "sound' he likes he can enter all control elements into the memory. To retrieve this sound or any other entered, the mechanical switch 101 is set into read mode and the relevant switch on the keypad 102 depressed. When this is done the presetable inputs of the counters 76 and the pick up latches (part of pick up logic unit 71) are loaded from the outputs of the RAM (100). All addressing and timing for these functions may be carried out by a timing and control circuit or CPU (central processing unit) 103.

Obviously, it is desirable if the RAM retains its contents while the guitar is not in use, so preferably the RAM is arranged so as to be non-volatile, e.g. by making it using a memory which is inherently non-volatile, or by using a memory with a very low power consumption and providing it with battery back-up.

Quite apart from the circuitry already described, it is also possible that electronic tuning circuits may be incorporated into the guitar. The state of tuning of the strings may, in one embodiment, be indicated by a set of display LEDs having inputs from the tuning circuitry and mounted for example in a circle on the front of the guitar. When tuning, a string is plucked and the vibration is picked up by the pick-ups. The signal from the pick-ups is then compared with a selected tuning signal or note generated in the tuning circuitry and the result of the comparison displayed by the LEDs. It is envisaged that when the note from a string is below that of the note being tuned to, the LEDs will light up consecutively in one circular direction (one LED being turned off as the next one is turned on) so that a circulating pattern of light is produced.If, on the other hand, the note from the string is too high, the LEDs will light up consecutively in the opposite direction. When the string is perfectly in tune a further LED or all the LEDs in the circle can be lit.

Figure 8 shows one form of on-board tuning display.

When a string to be tuned is plucked the signal from the bass (or neck) pick up is fed to a signal processing circuit 120 where it is filtered by a filter to remove unwanted harmonics and then further processed to produce a train of relatively short duration pulses synchronised with the filtered waveform. These pulse samples the data present at the inputs of a number of data latches and the outputs from these are used by LED drives 122 to drive an arrangement of LEDs 123 as previously described.

The display holds until new data is sampled. This data is derived from the outputs of a ring counter 124 which is clocked by a known reference n times the desired frequency of the string to be tuned.

This reference is produced by a crystal oscillator 125 driving the input of a musically related tone decoder circuit 126. The outputs of this decoder 126 can be selected by a mechanical switch 127 mounted at a convenient point on the instrument to provide for tuning to any one of a number of different notes. Also, this output reference may be divided to the same frequency as the string to be tuned by dividing 126 and can be fed to the output jack (connector) and can be suitably blended with the sound of the string for coarse tuning by ear.

The system employed can be as accurate as the reference oscillator and decoder circuit combination as there are no other processes introducing errors e.g. moving coil meters or frequency to voltage conversions.

With the structure as above described, there is provided a guitar which is of an extremely rigid structure having an integral beam whereby the natural resonant frequency of the guitar is raised well above that of the strings, whereby there is very little damping of the string movement during playing. Furthermore, this integral very rigid construction has been so incorporated into the guitar that there is no interference with the proper location of the pick-ups and yet there is adequate space for the receipt within the guitar of the electronic circuitry required. The guitar itself is provided with a good feel by the structural foam outer surface of the body and smooth finished surface of the stressed skin of the neck, the electronic circuitry itself being readily available for access by being mounted on a detachable back panel.

Claims

1. A stringed musical instrument having a body portion, at least one pick-up and, incorporated in the body portion, active electronic circuitry for receiving the output of the pick-up(s) and for processing the output of the pick-up(s) and/or assisting in tuning the strings of the instrument.

2. A stringed musical instrument according to claim 1 and having a neck and a headstock, the circuitry having means to receive signals from the pick-up(s), said neck, headstock and body portion being of a substantially unitary construction so to provide rigidity to said instrument.

3. An instrument according to claim 1 or 2 wherein said electronic circuitry includes a power supply.

4. An instrument according to claim 1, 2 or 3 wherein the circuitry is arranged to receive an electric supply via a lead and to deliver an output for amplification and/or further processing via the same lead.

5. An instrument according to any one of the preceding claims wherein there is a plurality of pick-ups and the circuitry is arranged to combine the outputs of the pick-ups.

6. An instrument according to claim 5 wherein the circuitry is arranged so as selectively to reverse the phase of one or more of outputs from the pickups relative to the remainder when combining the outputs therefrom.

7. An instrument according to claim 6 wherein user-operable switches are provided to set the relative phase of the combined pick-up signals.

8. An instrument according to any one of claims 5 to 7 wherein switching means are provided to enable the user to select the output from one or more individual pick-ups, or combinations thereof, for processing by the signal processing circuitry.

9. An instrument according to claim 7 or 8 wherein a display is provided on the body portion of the guitar indicating the current setting of the switch(es) and/or switching means.

10. An instrument according to claim 7, 8 or 9 wherein the circuitry incorporates memory means for storing the settings of the switches and/or of the switching means.

11. An instrument according to any one of the preceding claims wherein the circuitry includes frequency selective filtering circuitry.

12. An instrument according to any one of the preceding claims wherein there are one or more user-operable controls for setting signal processing characteristics of the circuitry.

13. An instrument according to claim 11 wherein, for at least one such control, the signal processing circuitry includes one or more counters of which the count represents the current setting of that control.

14. An instrument according to claim 13 wherein one or more alpha-numeric or other displays are provided to indicate current control settings.

15. An instrument according to claim 13 or 14 wherein means are provided for deriving an analogue signal from the output of the or each counter for controlling the characteristics of active filter circuits included in said circuitry.

16. An instrument according to any one of claims 11 to 15 and including memory means for storing control settings of the circuitry.

17. An instrument according to claim 10 or 17 wherein the memory means is arranged to store a plurality of sets of settings and means are provided for retrieving from the memory means a user-selected set of settings and for establishing current settings of the circuitry in accordance with them.

18. An instrument according to any one of the preceding claims wherein said circuitry for assisting in tuning the strings includes display means for displaying the state of tuning of the strings.

19. An instrument according to any one of the preceding claims wherein said circuit for assisting in tuning the strings has a user-operable control for selection of a frequency/note to which the strings are to be tuned.

20. An instrument according to claim 18 or 19 wherein the tuning assisting means is arranged to produce a moving light pattern whose direction, or sense, of movement is indicative of whether a particular string is tuned sharp or flat.

21. A stringed musical instrument constructed and arranged substantially as hereinbefore described with reference to and as illustrated by the accompanying drawings.