OCR GCE Physics B G496 Coursework (research report)

Research report for the qualification, OCR GCE Physics B (Advancing Physics)

March 2015

HOW DO ELECTRIC GUITAR PICKUPS WORK?

By

Maurice Yap

Peter Symonds College

2

How do electric guitar pickups work?

TABLE OF CONTENTS1. Introduction................................................................................1

1.1. The concept of pickups....................................................................................................1

2. Electromagnetic induction.........................................................2

3. Resonant peak.............................................................................3

3.1. Factors affecting the resonant peak................................................................................4

3.1.1. Active pickups...........................................................................................................5

4. Hum-cancelling...........................................................................5

4.1. Humbucking pickups.......................................................................................................6

4.1.1. Waveform models of the signals in a humbucker......................................................6

4.1.2. Advantages and disadvantages of humbucking pickups...........................................8

4.2. Hum-cancelling in single-coil pickups.............................................................................8

4.2.1. Single-coil pickup noise cancellation in a Stratocaster-style guitar.........................9

4.2.2. Single-coil pickup noise cancellation in a Telecaster-style guitar...........................10

5. Conclusion................................................................................10

6. Reference List...........................................................................11

7. Bibliography..............................................................................12

8. Evaluation of sources................................................................13

LIST OF FIGURESFigure 1: Rickenbacker Electro A-22, the "Frying Pan" guitar (Doryfour, 2012)....................................1Figure 2: A single coil alnico pickup on a Fender Telecaster guitar (own image)...................................2Figure 3: A direct injection box (own image)...........................................................................................2Figure 4: Graph of e.m.f. against time (own diagram).............................................................................3Figure 5: The basic specifications of a two-bar humbucking pickup as published on its manufacture’s website (Seymour Duncan, 2007)............................................................................................................3Figure 6: The spectrogram plot of the frequency spectrum of a plucked guitar sting, with amplitude on the vertical axis and frequency on the horizontal axis (McClung, 2009).................................................4Figure 7: A humbucking alnico pickup on a Fender Jazz Bass guitar (own image).................................5Figure 8: Waveforms of the components of the electrical signal from the first coil of a humbucker when a note is played (own diagram)......................................................................................................6Figure 9: Waveforms of the components of the electrical signal from the second coil of a humbucker when a note is played (own diagram)......................................................................................................7Figure 10: Waveforms of the noise signals in the coils of a humbucker (own diagram)..........................7Figure 11: Waveform of the coils in a humbucker when a note is played (own diagram).......................8Figure 12: The body of a Stratocaster-style guitar (own image).............................................................9Figure 13: The body of a Fender Telecaster guitar (Vintage & Rare, n.d.).............................................9Figure 14: The pickup positions of a standard Stratocaster-style electric guitar, starting with position 1 on the far left (own image)....................................................................................................................9

GCE Physics – G496 Researching Physics | Maurice Yap 6946

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Figure 15: The pickup positions of a standard Telecaster-style electric guitar, starting with position 1 on the far left (own image).....................................................................................................................10


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1.INTRODUCTIONThe electric guitar was introduced in the early 20th century to enable guitarists to be loud enough in jazz and dance bands, to compete with the high volume of instruments like horns (trumpets, trombones and saxophones) and the drum kit. It had been the case that guitars were modified to acoustically enhance and increase their volume. For example, in 1927, the Los-Angeles based company, National, produced resonator guitars with metal discs in the body to acoustically amplify the sound (Bacon, 2000, p.13). Also, guitars were built with larger bodies for this reason, but they were harder and much more uncomfortable to play.

To solve this problem, the idea of using a pickup to electronically amplify the sound of the string through a loudspeaker was introduced in the 1920s and 1930s. The earliest guitar built with this concept in mind which had any sort of big influence was created by Paul Barth and George Beauchamp in 1931 (Bacon, 2000, p.13). It became the Rickenbacker Electro A-22 – the Rickenbacker firm’s first production model and the first ever guitar to use an electromagnetic pickup. It was nicknamed the “Frying Pan” because of its appearance. It can be seen below in figure 1.

FIGURE 1: RICKENBACKER ELECTRO A-22, THE "FRYING PAN" GUITAR (DORYFOUR, 2012)

The electric guitar was born, along with famous and influential manufacturers like Gibson, Fender and Ibanez; for the rest of the 20th century right up to today, the electric guitar has formed the basis of the rock, metal and blues strands of music and also massively impacted and contributed to the sound of jazz, funk, country, soul and pop music.

1.1.THE CONCEPT OF PICKUPSPickups are devices attached to the body of an electric guitar beneath the strings to sense the vibrations of the strings and send this as an electrical signal to be amplified. An example of one is shown in figure 2. They work using electromagnetic induction and consist of very thin enamel or polymer-coated copper wire that is wound thousands of times around either magnetic pole pieces that lie directly under each string (made of metallic alloys like alnico) or a ceramic bar magnet that lies beneath all the strings (WillsEasyGuitar, 2014). This forms the coil through which an electromotive force and current are induced (Brian, 2002). The


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two ends of this coil are connected to a circuit inside the body of the guitar. The electrical signal is transferred through a cable called a jack lead, which is plugged into the guitar at one end, and at the other end, optional auxiliary effects pedals and the amplification system, which could take the form of a guitar amplifier, headphone amplifier or a direct injection box (figure 3) or system for recording and live musical performances.

LEFT – FIGURE 2: A SINGLE COIL ALNICO PICKUP ON A FENDER TELECASTER GUITAR (OWN IMAGE)

RIGHT – FIGURE 3: A DIRECT INJECTION BOX (OWN IMAGE)

2.ELECTROMAGNETIC INDUCTIONThe bar magnet of magnetic pole pieces under each string work to form a magnetic field away from the guitar and through the strings (Woodford, 2014). Because electric guitar strings are made using ferromagnetic metals like cobalt, nickel and iron or alloys which contain ferromagnetic metals like steel, they themselves become magnetised and affect the magnetic field.

Faraday’s Law of Electromagnetic Induction states that a voltage will be induced in a coil of wire when there is a change in the magnetic field around it (Nave, n.d.a). This induced voltage is known as the electromotive force (e.m.f.). When this coil forms part of a closed circuit, a current is induced on the circuit. The induced e.m.f. is equal to the rate of change of the flux linkage passing through the coil.

Lenz’s law states that the direction of the induced e.m.f. and current are opposite to the change that caused it (Breithaupt, 2010, pp. 269-270).

The flux linkage of the coil is the product of the total magnetic flux passing through the coil and the number of turns on the coil.

In differential form, combining these together gives the following equation, where ε is the e.m.f., Φ is the total magnetic flux, t is time and N is the number of turns on the coil (CGP Books, 2009, pp. 48-49):


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ε=−ddtΦN

In the context of an electric guitar, the plucking of one or more of the strings causes it to vibrate as it is under tension. They vibrate perpendicular to the magnetic field of the pickup’s magnets and cut through its lines of flux. Because the strings are magnetised, it causes the magnetic field through the coil to oscillate (Schuster, 2013). Because this field is perpendicular to the coil, the lines of magnetic flux are cut by the coil and so an e.m.f. is induced in the coil. Due to Lenz’s law, the direction of the induced voltage and current will swap as the movement of the string changes direction.

The rate of change of flux through the coil is determined by the velocity at which the magnetic field is oscillating, and hence also, the velocity of the guitar string. The movement of the plucked string can be modelled by simple harmonic motion because it oscillates either side of a midpoint and there is force pulling the string back towards its midpoint (CGP Books, 2009, p.12). The graph of velocity against time takes the shape of a sine or cosine curve and therefore, the graph of induced voltage (e.m.f.) against time must also take this shape. In figure 4, the length of time marked with T represents the time period of one oscillation.

t

ε

FIGURE 4: GRAPH OF E.M.F. AGAINST TIME (OWN DIAGRAM)

It can be deduced that the frequency, 1T

(Breithaupt, 2010, p.13), of the vibration of the

string (i.e. its musical pitch) is exactly equal to the frequency of the alternating e.m.f. Because this is the electrical signal that is amplified, the amplified sound has the same musical pitch as the plucked string sounds acoustically.

3.RESONANT PEAKThe wire of a pickup coil has an amount of impedance, a resistance to alternating current. It is determined, in part, by the resistance (to direct current) of the wire, which slows down the electrons moving through the wire, and therefore decreases the current (Archer & Pavlic, 2002). This imposes a limit on the minimum time period for a change in the direction of the current, while the oscillation generates a large enough electrical signal to be audible when amplified. This is because the electrons cannot move quickly enough. Hence, there is an


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upper limit to the frequency at which the electrical signal can oscillate and still be audible when amplified. This frequency is known as the resonant peak (WillsEasyGuitar, 2014).

FIGURE 5: THE BASIC SPECIFICATIONS OF A TWO-BAR HUMBUCKING PICKUP AS PUBLISHED ON ITS MANUFACTURE’S WEBSITE (SEYMOUR DUNCAN, 2007)

This resonant peak is one of the most important characteristics that determines the tone of an electric guitar pickup. This is because the vibration pattern of a plucked string does not consist only of the sinusoidal wave with the frequency of the musical note played, but in fact, a whole spectrum of frequencies, which has a shape that gives a guitar its distinctive sound. It is this that distinguishes, for example, the sound of a clarinet from that of a trumpet or from a vibraphone, all of which are playing the same musical note. The resonant peak is one of the most important specification considered by guitarists when they buy a pickup. Figure 5, a screenshot from Seymour Duncan’s online shop, exemplifies this.

FIGURE 6: THE SPECTROGRAM PLOT OF THE FREQUENCY SPECTRUM OF A PLUCKED GUITAR STING, WITH AMPLITUDE ON THE VERTICAL AXIS AND FREQUENCY ON THE HORIZONTAL AXIS

(MCCLUNG, 2009)

The frequencies higher than the resonant peak are inaudible. This gives the effect that a high resonant peak gives a brighter sound that is suitable for use in genres like rock and funk, while a low resonant peak gives a warmer and mellower sound which is ideal for jazz. It can be seen in figure 6 that a plucked acoustic guitar string produces frequencies well above 11 kHz. However, most manufactured guitar pickups generally have a resonant peak


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of between 2 kHz and 5 kHz (Gallagher, 2012, p.53) and so much of the top-end of a plucked guitar string’s sound is lost from the output signal.

3.1.FACTORS AFFECTING THE RESONANT PEAKBecause the resistance of the coil of a pickup determines its resonant peak, relationships between resonant peak and factors can be derived from the equation for resistance, where ρ is the resistivity of the wire, R is the resistance, A is the cross sectional area of the wire and l is the length of the wire (CGP Books, 2008, p.34):

ρ=RAl⇒R= ρ l

A⇒ {R∝ ρR∝ l

R∝ 1A

Firstly, it can be deduced that as resistance is directly proportional to resistivity, a coil made using wire of a lower resistivity would raise the frequency of the resonant peak. Next the proportionality between resistance and length implies that decreasing the length of the wire would also decrease the resistance and raise the resonant peak. Finally, because the resistance is inversely proportional to the cross-sectional area of the wire, a thicker wire would decrease the total resistance and increase the resonant peak.

In the context of an electric guitar pickup, these factors have a general limitation that there is a trade-off between the brightness of its tone (i.e. how high the resonant peak is) and the strength of the electrical signal (i.e. the output voltage). It was determined in section 2 that the output e.m.f. is directly proportional to the number of turns in the coil. It is important for a guitar to have a significantly high output voltage as it must be able to be transmitted through a long jack lead cable and still be strong enough to drive an amplifier circuit (EMG Pickups, 2001). Due to resistance in the cable, the longer the cable, the more voltage is lost. Another reason why a high voltage is desirable is that a high voltage gives a higher signal-to-noise ratio. This means that the player is able to increase the gain and/or volume of their amplifier without introducing a large amount of noise.

Increasing the number of turns by increasing the length of the wire would lower the resonant peak (with all other factors remaining equal). Furthermore, increasing the thickness of the coil’s wire (i.e. cross-sectional area) to raise the resonant peak would cause the number of turns in the coil to decrease, as it is physically limited by the size of the pickup. The factor of resistivity is not one that can easily be changed as copper is the metal used in almost all pickups because it has the lowest resistivity of materials that are suitable and practical for this purpose in terms of cost, availability and physical properties.

3.1.1.ACTIVE PICKUPS

However, there is in fact a way that pickups can be manipulated to produce a high output voltage while not compromising the range of frequencies produced: active pickup systems. These involve pickups with a smaller number of turns in the coil and therefore, a low impedance and so a high resonant peak. A small amplifier circuit is built into the shell of the


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pickup, which boosts the electrical signal and increases the voltage that is transmitted through the jack lead, usually using a 9-volt battery inside the body of the guitar. Because the electrical signal of the pickup only has to travel a very small distance (because the amplifier circuit is built close to the coil), the very low output voltage is not a problem (EMG Pickups, 2001).

There are significant disadvantages of active pickups. One is that active pickups are generally more expensive that passive ones, due to the extra circuitry. As well as this, the fact that an active pickup requires a battery to work means that it requires replacing (Slash&roses, 2012). In addition to the pitfall of the extra cost of batteries, the signal from active pickups fade very quickly when the battery is low, meaning that players can have pickups fail while performing on stage without prior warning due to the battery having run out.

4.HUM-CANCELLING

FIGURE 7: A HUMBUCKING ALNICO PICKUP ON A FENDER JAZZ BASS GUITAR (OWN IMAGE)

Most guitar pickups are either single coil – as seen in figure 2 – or humbuckers – as can be seen above in figure 7. A major pitfall of single coil pickups is that they are susceptible to sensing and outputting magnetic noise (WillsEasyGuitar, 2014), known colloquially as hum, because of the sound that this magnetic noise gives. For example, in the household, the vast majority of appliances, like computers, televisions and sound systems, use transformers to convert alternating mains current into direct current. They create an alternating magnetic field around them. This noise is also present in performance venues, like concert halls, places of worship and pubs. Many use radio transmitters and receivers in wireless microphones or communications systems. Electronic equipment on a stage, like keyboards, pedal boards and synthesisers also uses alternating current transformers. Moreover, the microwaves of mobile phones commonly induce a very distinct and displeasing signal into pickup coils.

4.1.HUMBUCKING PICKUPSHumbucking pickups combat this by using two adjacently-placed coils that are connected in series. The two coils are wound in opposite directions. This means that their signals are identical but have a phase difference of π radians and so are in antiphase to each other. Phase cancellation therefore occurs to the superposed signals and due to destructive


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interference, the unwanted magnetic background noise is eliminated. However, this would also mean that the vibration of the guitar string is also lost. This problem is solved by making it so that the magnets in each coil have opposing polarities (i.e. one is north-seeking and the other is south-seeking), changing the phase of the vibrating spring by π radians on one of the coils (Trynka, 2002, p.55; Breithaput, 2010, pp. 13-14).

In summary, humbucking pickups remove noise from the output signal using destructive interference, but the signal of the guitar strings is kept through constructive interference. This also has the effect of increasing the strength of the guitar string signal, which is why humbucking pickups generally have a higher voltage than single coils.

4.1.1.WAVEFORM MODELS OF THE SIGNALS IN A HUMBUCKERAll diagrams in figures 8 to 11 have a horizontal time axis and a vertical axis for voltage. They are models of the electrical signals in the coils of a single humbucking pickup that consists of two coils.

FIGURE 8: WAVEFORMS OF THE COMPONENTS OF THE ELECTRICAL SIGNAL FROM THE FIRST COIL OF A HUMBUCKER WHEN A NOTE IS PLAYED (OWN DIAGRAM)

Figure 8 shows the electrical signals in the first coil of a humbucker when a single note is played by plucking a string. The top left graph shows the noise signal, simulating unwanted background magnetic signals. The top right graph shows the pure signal produced due to the vibration of the guitar string, while the bottom graph shows these two signals superposed, which is what would be the output signal of the first pickup coil.


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FIGURE 9: WAVEFORMS OF THE COMPONENTS OF THE ELECTRICAL SIGNAL FROM THE SECOND COIL OF A HUMBUCKER WHEN A NOTE IS PLAYED (OWN DIAGRAM)

Figure 9 shows the electrical signals in the second coil of a humbucker at exactly the same time as figure 8. The top left graph shows the noise signal, which is the same as that of the first coil, but inverted (phase difference of by π radians). The top right graph shows the signal of the guitar string’s vibration. Notice that it is in phase with, and therefore identical, to that of the first coil as it is in phase. The bottom graph shows these two signals superposed, which is what would be the output signal of the second pickup coil.

FIGURE 10: WAVEFORMS OF THE NOISE SIGNALS IN THE COILS OF A HUMBUCKER (OWN DIAGRAM)

Figure 10 illustrates what happens in a humbucking pickup when the player is not playing. The top left and top right graph are the noise signals from the first and second coils respectively. The bottom graph shows these two superposed – what happens in a humbucker of two coils wired in series. The horizontal straight line represents no change in voltage and therefore, no electrical signal. In terms of sound, the humbucker produces silence when this signal is amplified.


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FIGURE 11: WAVEFORM OF THE COILS IN A HUMBUCKER WHEN A NOTE IS PLAYED (OWN DIAGRAM)

Figure 11 shows the signals of the two coils when a single note is played (top left and top right). Because the noise signals are in antiphase, it is eliminated. The two sinusoidal waves of the vibrating string are in phase, and therefore constructively interfere to give a sinusoidal wave with a larger voltage amplitude than each coil individually, but with no noise. This is the output signal of a humbucking pickup.

4.1.2.ADVANTAGES AND DISADVANTAGES OF HUMBUCKING PICKUPSHumbucking pickups use two coils and so in total, have roughly double the number of turns of a single coil pickup. This means that the total length of wire in a humbucker is roughly double that of a single coil and so the total resistance is also roughly double and the resonant peak is much lower.

Also, the higher output voltage of humbucking pickups means that a more powerful signal is received by an amplifier. This can be a problem for cheaper amplifiers where the pre-amp has a fixed gain; the powerful signal can overload the components in these pre-amp circuits and distort the sound.

Together, these two features – high output and low resonant peak – mean that humbucking pickups give a deeper, warmer and fuller sound than single coil pickups. This sound may be desirable or undesirable, depending on the player’s application of their guitar and tonal preferences.

The very high signal-to-noise ratio of humbucking pickups makes is ideal for use in metal music. Because of the genre’s characteristic sound, the gain on guitar amplifiers are turned up very loud to produce a heavily distorted sound. Having humbucking pickups means that this can be done without having too much noise in the sound coming from the amplifier. The higher frequencies in the tone of a guitar is also much less important in the metal genre, and so the lower resonant peak of humbuckers does not pose a problem.

4.2.HUM-CANCELLING IN SINGLE-COIL PICKUPSNoise-cancellation is also applied to single coil pickups using the same principle as the two coils in a humbucker. Two separate pickups have coils wound in opposite directions, but use


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magnets with opposite polarities, like in a humbucker. Although this does reduce the unwanted noise, it is much less effective than a humbucking pickup as the two pickups sense the string (and therefore the unwanted magnetic signals in the environment) at a much greater distance apart. Taking advantage of this also has implications on the tone of the sound. In addition to the increased resonant peak, using two single coil pickups simultaneously may force the player to compromise their desired tone. The further away a pickup is away from the bridge of the guitar, the warmer and less bright the sound it produces, and conversely, the further away from the neck of a guitar a pickup is, the less warm and full its sound. A player therefore cannot use these two extremes in tone and take advantage of hum-cancellation.

LEFT – FIGURE 12: THE BODY OF A STRATOCASTER-STYLE GUITAR (OWN IMAGE)

RIGHT – FIGURE 13: THE BODY OF A FENDER TELECASTER GUITAR (VINTAGE & RARE, N.D.)

4.2.1.SINGLE-COIL PICKUP NOISE CANCELLATION IN A STRATOCASTER-STYLE GUITARAs can be less in figure 12, the standard pickup arrangement for a guitar designed using the model of Fender’s Stratocaster guitar is three single-coil pickups – neck, middle and bridge (corresponding to the pickups at the top, middle and bottom of the body in figure 12). The neck and bridge pickups have the same configuration in terms of the direction in which the coil is wound and the polarity of the magnetic pole-pieces. The middle pickup has the opposite configuration. A five-way switch is used to select the pickup(s) that are included in the output signal. Figure 14 shows each of the five possible positions of this switch. Table 1 shows the pickup selection of each switch position.

FIGURE 14: THE PICKUP POSITIONS OF A STANDARD STRATOCASTER-STYLE ELECTRIC GUITAR, STARTING WITH POSITION 1 ON THE FAR LEFT (OWN IMAGE)


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Switch position Pickup(s) selected Hum cancellation? Tone1 Neck No 2 Neck and middle Yes Warmer3 Middle No4 Middle and bridge Yes Brighter5 Bridge No

TABLE 1: SWITCH POSITION CONFIGURATIONS OF A STANTARD FIVE-WAY STRATOCASTER PICKUP SWITCH

4.2.2.SINGLE-COIL PICKUP NOISE CANCELLATION IN A TELECASTER-STYLE GUITARFigure 13 shows that the standard pickup arrangement for a guitar designed using the model of Fender’s Telecaster guitar is two single-coil pickups – neck and bridge (corresponding to the pickup at the top and bottom of the guitar body in figure 13). The neck and bridge pickups are wound in opposite directions and have magnets with opposing polarities. A three-way switch is used to select the pickup(s) that are included in the output signal. Figure 15 shows each of the three possible positions of this switch. Table 3 shows the pickup selection of each switch position.

FIGURE 15: THE PICKUP POSITIONS OF A STANDARD TELECASTER-STYLE ELECTRIC GUITAR, STARTING WITH POSITION 1 ON THE FAR LEFT (OWN IMAGE)

Switch position Pickup(s) selected Hum cancellation? Tone1 Neck No Warmer2 Neck and bridge Yes3 Bridge No Brighter

TABLE 2: SWITCH POSITION CONFIGURATIONS OF A STANDARD THREE-WAY TELECASTER PICKUP SWITCH

5.CONCLUSIONThis report has shown that through the application of several ideas and concepts from within the subject of physics, the creation and enhancement of probably the most influential device to music in the last century has been made possible. While electromagnetic induction is the foundation of a pickup’s workings, the use and thorough understanding of other areas of physics involved – resonant peak and phase are just two of these – have developed it from very simple and crude 1920s and 1930s prototypes, into much more sophisticated


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components, with a very large market that has a wide range of pickups available to the consumer.

The availability of information about the physics behind guitar pickups has also allowed musicians, who may not necessarily have a background in science, to understand such concepts. They are now more informed about how different factors affect the operation of and sound produced by a pickup, enabling them to select and use pickups to suit their desired preferences and uses.


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6.REFERENCE LISTArcher, M. & Pavlic, T. (2002) What is the difference between resistance and impedance?. [Online]. 1 October 2002. PhysLink.com. Available from: http://www.physlink.com/Education/AskExperts/ae517.cfm [Accessed: 26 February 2015].

Bacon, T. (2000) Electric Guitars: The Illustrated Encyclopedia. United Kingdom, Outline Press Ltd.

Breithaupt, J. (2010) Physics. 3rd edition. United Kingdom, Palgrave Macmillan.

Brian, M. (2002) How Electric Guitars Work. [Online]. 1 July 2002. HowStuffWorks.com. Available from: http://entertainment.howstuffworks.com/electric-guitar1.htm [Accessed: 28 January 2015].

CGP Books (2009) A2 Physics OCR B Complete Revision & Practice. Amy Boutal, Sarah Hilton, Alan Rix, Julie Wakeling, et al. (eds.). United Kingdom, Coordination Group Publications Ltd (CGP).

CGP Books (2008) AS-Level Physics OCR B (Advancing Physics) Complete Revision & Practice. Amy Boutal, Julie Wakeling, & Sarah Williams (eds.). United Kingdom, Coordination Group Publications Ltd (CGP).

Doryfour (2012) File:Rickenback Frying Pan aluminum-cast guitar (1934).jpg. [Online]. 22 April 2012. Wikimedia Commons. Available from: http://commons.wikimedia.org/wiki/File:Rickenback_Frying_Pan_aluminum-cast_guitar_(1934).jpg [Accessed: 26 February 2015].

EMG Pickups (2001) FAQ. [Online]. 1 February 2001. EMG Pickups. Available from: http://www.emgpickups.com/faq [Accessed: 27 February 2015].

Gallagher, M. (2012) Guitar Tone: Pursuing the Ultimate Guitar Sound. United States, Course Technology.

McClung, D. (2009) New adventures with music. [Online]. 20 December 2009. Embracing the Random. Available from: https://daveinthewest.wordpress.com/2009/12/20/new-adventures-with-music/ [Accessed: 26 February 2015].

Nave, C.R. (n.d.a) Faraday’s Law. [Online]. HyperPhysics. Available from: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/farlaw.html [Accessed: 13 February 2015a].

Schuster, D. (2013) Doc Physics - Electric Guitar Pickup Coil to Amplifier to Speaker Voice Coil Theory. YouTube. [Online]. Available from: https://www.youtube.com/watch?v=-colsdWF4-s [Accessed: 25 February 2015].

Seymour Duncan (2007) Warren DeMartini RTM, bridge. [Online]. 1 September 2007. Seymour Duncan. Available from: http://www.seymourduncan.com/products/custom-shop/artists-signatu/warren_demartin/ [Accessed: 28 January 2015].

Slash&roses (2012) Active Vs Passive Pickups | Guitar Columns. [Online]. 20 January 2012. Ultimate-Guitar.Com. Available from: http://www.ultimate-guitar.com/columns/the_guide_to/active_vs_passive_pickups.html [Accessed: 1 March 2015].

Trynka, P. (2002) The electric guitar: an illustrated history. United Kingdom, Virgin Books.

Vintage & Rare (n.d.) Fender TELECASTER ’52 Heavy Relic Custom Shop Team Built 2011 Red Sparkle Guitar For Sale. [Online]. VintageandRare.com. Available from:


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http://www.vintageandrare.com/product/Fender-TELECASTER-52-Heavy-Relic-Custom-Shop-Team-Built-2011-Red-Sparkle-38045 [Accessed: 1 March 2015].

WillsEasyGuitar (2014) How guitar and bass pickups work and why it matters. YouTube. [Online]. Available from: https://www.youtube.com/watch?v=EnHH6Uke090 [Accessed: 28 January 2015].

Woodford, C. (2014) Electric guitars. [Online]. 18 June 2014. Explain That Stuff. Available from: http://www.explainthatstuff.com/electricguitars.html [Accessed: 25 February 2015].


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7.BIBLIOGRAPHYBBC (2006) Making electricity. [Online]. 15 September 2006. BBC Bitesize. Available from: http://bbc.co.uk/schools/gcsebitesize/science/add_ocr_pre_2011/electric_circuits/mainsproducedrev1.shtml [Accessed: 28 January 2015].

Beauchamp, G.D. (1937) Electrical stringed musical instrument. [Online]. Available from: http://www.google.com/patents/US2089171 [Accessed: 25 February 2015].

Breslyn, W. (2013) Is Nickel Magnetic?. [Online]. 17 October 2013. Magnets and Magnetism. Available from: http://terpconnect.umd.edu/~wbreslyn/magnets/is-nickel-magnetic.html [Accessed: 25 February 2015].

Corfe, J. (2011) Electromagnetic Induction. [Online]. 16 April 2011. MrCorfe.com. Available from: http://www.mrcorfe.com/KS4/AQA/Phy3/Electromag/Induction.php [Accessed: 11 February 2015].

Electrical4u (2013) Faraday Law of Electromagnetic Induction. [Online]. 18 May 2013. Electrical4u. Available from: http://electrical4u.com/faraday-law-of-electromagnetic-induction/ [Accessed: 13 February 2015].

Irons, R. (2012) How Hum-Cancelling Works, Part 1. [Online]. 7 September 2012. Seymour Duncan. Available from: http://www.seymourduncan.com/blog/the-tone-garage/how-hum-cancelling-works-part-1/ [Accessed: 28 February 2015].

Lowe, T.L. & Rounce, J.F. (2002) Calculations for A-level Physics (Calculations For A Level Physics). United Kingdom, Nelson Thornes Ltd.

Nave, C.R. (n.d.b) Guitar Pickups and Harmonic Content. [Online]. HyperPhysics. Available from: http://hyperphysics.phy-astr.gsu.edu/hbase/music/eguit.html [Accessed: 28 January 2015b].

Seed, M., Shepherd, J. & Horn, D. (2003) Continuum Encyclopedia of Popular Music of the World: v. 2: Production and Performance. John Shepherd, David Horn, Paul Oliver, & Peter Wicke (eds.). United Kingdom, Continuum International Publishing Group Ltd.


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8.EVALUATION OF SOURCESSource Type Reliability

Archer & Pavlic, 2002

Web page

Two answers by undergraduate students Martin Archer was a Physics student at Imperial College London, and is therefore likely to be

very well informed about impedance Ted Pavlic was an Electrical Engineering student at Ohio State University, and his studies

specialise in this topic area Although the information in the two answers agree with each other, they are unlikely to have

been cross-checked by others; this could be a source of unreliability

Bacon, 2000 Book

Published hardback book, so it has been checked and edited by multiple people It is a book primarily about the musical aspect of electric guitars, and so the information

about physics may be of a lower quality Published 15 years ago, so it does not provide information on the very latest technical

innovations

BBC, 2006 Web page

The BBC is a publicly-funded organisation, and is therefore tightly regulated, meaning that it is likely that the information they publish has been checked for accuracy

Used across the country by many GCSE Science students, so it should be a very reliable source

Beauchamp, 1937

Patent Not applicable – this is the original patent and is therefore a primary source

Breithaupt, 2010 Book

Popular physics text book with information of a very wide range of physics topics Probably very thoroughly researched Published book so it has been checked by multiple people to ensure accuracy Updated recently so information is not out-of-date Jim Breithaupt is an experienced physics writer who was formerly a senior teacher at a large

sixth form college and A-level Physics examiner, so is a reliable source

Breslyn, 2013 Web page

Updated recently so information is not out-of-date Wayne Breslyn is a scientific researcher at the University of Maryland and has a PhD, so is

well-informed The website’s content probably has not been checked by other people, which could

compromise reliabilityBrian, 2002 Web page Marshall Brian has degrees in Electrical Engineering and Computer Science, so is well-

educated and is knowledgeable on the subject


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The website has many writers, so the content probably has been checked and edited

CGP Books, 2009 Book

An A-level revision guide aimed at students, so it has been cross-checked for accuracy of information

CGP is a very popular brand with educational institutions and so is likely to be an accurate source of good quality information

This particular book is on the reading list for A2 Physics at my college, which was compiled by teachers in the Physics department, who are all well-educated, very competent and extremely knowledgeable

CGP Books, 2008 Book

An A-level revision guide aimed at students, so it has been cross-checked for accuracy of information

CGP is a very popular brand with educational institutions and so is likely to be an accurate source of good quality information

This particular book is on the reading list for AS Physics at my college, which was compiled by teachers in the Physics department, who are all well-educated, very competent and extremely knowledgeable

Corfe, 2011 Web page

The website of Jon Corfe, my old GCSE Physics teacher, which he uses for teaching The content of the website is likely to have been cross-checked by many knowledgeable

science teachers over many years, to ensure the reliability of the information, as it is frequently used by GCSE students

Doryfour, 2012 Web page Not applicable – source was only used for an image and was not used for information

Electrical4u, 2013

Web page Updated recently so information is not out-of-date The site has been produced by a diverse range of experienced electrical engineers Their expertise in the subject area suggests the information is accurate and reliable

EMG Pickups, 2001

Web page

EMG is a very well-known company that specialises in active pickups – the subject of the information which the source was used for

EMG is successful and spends a lot of money on marketing, suggesting that its website’s information has been well researched and cross-checked by experts in this field

EMG sells active pickups, so there may be some bias to exaggerate their advantages and vice versa

Gallagher, 2012 Book

Updated recently so information is not out-of-date Mitch Gallagher has written many good quality books on music technology He has worked in the music industry for many years in different roles and so is very

knowledgeable on guitar tone Reliable source of information about guitar tone, though maybe less so on physics Published book so it has been checked by multiple people to ensure accuracy

Irons, 2012 Web page Updated recently so information is not out-of-date


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The page is from Seymour Duncan’s official blog The writer is an employee of Seymour Duncan, a company with a very large share of the

market for guitar pickups The depth, clarity and supporting images of the article suggest that it is a reliable source of

information

Lowe & Rounce, 2002

Book

Published book so it has been checked by multiple people to ensure accuracy The co-authors are likely to have been educated to a high level in physics It is likely that the information in the book has been researched from and cross-checked

across multiple sources The book is aimed at A-level students, so the publisher has probably required that it be

checked thoroughlyMcClung, 2009 Web page Not applicable – source was only used for an image and was not used for information

Nave, n.d.a Web page The webpages are undated and I haven’t been able to date them, so it is unknown how up-to-

date the information is The website was produced by Rod Nave, a physics professor at Georgia State University, so

it is likely to be reliable It is unknown whether the content has been checked and edited by other people

Nave, n.d.b Web page

Schuster, 2013 Online video

Updated recently so information is not out-of-date Doc Shuster is an American High School teacher, and so is very well-informed about the

physics involved in my topic area Probably reliable

Seed et al., 2003 Book Published book so it has been checked by multiple people to ensure accuracy Large encyclopaedia that has probably been well-researched and checked and edited by

multiple competent peopleSeymour Duncan, 2007

Web page Not applicable – source was only used for an image and was not used for information

Slash&roses, 2012

Web page

User-generated content, so may have biased opinions A very popular article on Ultimate-Guitar.Com, a very popular website for electric guitarists,

so the content has been read and approved by many Writer probably has no background in physics, so the source is probably unreliable for

information on physicsTrynka, 2002 Book Strong focus on the musical and historical aspects of the electric guitar, as opposed to

physics A diverse team of expert writers and journalists contributed to the content, so it is reliable

for assessing historical and social aspects Questionable reliability, so the information given has been cross-checked with other sources


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Published book so it has been checked by multiple people to ensure accuracyVintage & Rare, n.d.

Web page Not applicable – source was only used for an image and was not used for information

WillsEasyGuitar, 2014

Online video

Recently uploaded video so information is up-to-date It is unknown whether the producer has a background in physics, since he is primarily a

guitarist Questionable reliability, so the information given has been cross-checked with other sources

Woodford, 2014 Web page

Updated recently so information is not out-of-date Writer is an experienced science writer with many published books on science, which have

won many prestigious awards Chris Woodford has an MA from Cambridge University and specialised in physics


Documents

OCR GCE Physics B G496 Coursework (research report)