All about pickups Part 1

All my life I've tried to get a particular sound from particular guitars, I knew what I wanted from a Strat, or from a Les Paul, did I get it - Definitely NOT, it took many years swapping out, taking a punt, then taking another punt, but if you're smart you can limit the number of punts you take.





So pickups then...What on earth are they? how do they work and why do some folk pay £7.6k for an original pair of PAFs?



I thought I know just the guy to clear up any confusion... Peter from Tone Chasers


What are they? What do they do? How do they do it?




There are 2 parts of this system that act as transducers transforming movement (kinetic) energy into electrical energy (in the case of the pickup) and electrical energy into movement (kinetic) energy (in the case of the speaker).

Similarly, to a speaker a pickup contains a coil or coils of thin wire, a magnet and some other supporting parts to hold the pickup together.

Most electric guitar pickups work on the principal of magnetic induction. Simply stated a magnet moving in the proximity of a coil induces a voltage into the coil. I’m sure you all remember from basic physics the experiment where you have a coil of wire hooked up to a voltmeter and when you thrust a magnet into the coil you see the voltmeter dial move. This is essentially the same principal in action.

In the case of electric guitar magnetic pickups the magnet is used to create a magnetic field in which the ferric strings sit (magnetising them). Near to the magnet (I shall explain this vagueness later when we come to the different types of pickups) is a wound coil of very fine wire. When the (now magnetic) string is struck and vibrates this moves in the vicinity of the coil of wire and induces a voltage into the coil. This then goes off through your volume, tone and jack socket to the amplifier.


That's the theory over...



History and why are there so many different types?


In the beginning

Why did pickups need to be invented?

As dance music became more popular, the poor old jazz guitar or acoustic guitar just wasn't loud enough, and just sticking a microphone in front of it, wasn't a great idea, as the guitarist had to sit still, and fight feedback, and more than ;likely you still couldn't hear him, and if you could it sounded awful.


So to try and get heard and to get some freedom from the back of the orchestra the pickup was inevitable...Peter explains...


Many of the different types of pickup designs came about to resolve design faults in the existing available pickups. Initially pickups where created from taking the old transducers from telephone mouthpieces and placing these near to the strings, electrifying acoustic guitars. The first truly electric stringed instruments were lap steel guitars and these used pickups with 2 C shaped magnets like the Rickenbacker ‘frying pan’ (1932)





Les and his thirst for sound

Although suitable for lap steels these were very expensive and labour intensive to produce also quite heavy if to be incorporated into an instrument designed to be played standing up.

In 1940 Les Paul revisited his experiments around building a solid body guitar (initially with a piece of railway track) and came up with ‘the log’ which had two hand wound pickups. He approached Gibson with the design in 1941 but they were not interested. They saw no future in electric guitars especially ones that didn’t look like a guitar (which s why he added the removable wings).




Leo and his vision

In 1948 Leo Fender was designing his first solid body guitar as he saw the potential of an electric guitar in the dance halls of the day to be amplified to a volume suitable to be heard. This was released in 1950 as the Fender Esquire (initially a ‘snakehead’ design in 1949 prototype) with a single bridge single coil pickup (essentially an overwound telecaster pickup).

This design later in 1950 added another single coil pickup in the neck position to become the Broadcaster and later the name changed to Telecaster after a copyright claim by Gretsch.

The Telecaster pickup set has some interesting design points that affect the sound.

The bridge pickup consists of magnetised Alnico 5 individual pole pieces, N pole up, length staggered to normalise the volume of signal between strings. A coil of 43AWG plain enamel wire, around 8000 turns counter clockwise (8kΩ) and a metal baseplate.

The neck pickup consists of magnetised Alnico 5 individual pole pieces, S pole up, flat poles. A (short, squat) coil of 43AWG wire, around 8000 turns counter clockwise (7.7kΩ) and a metal cover.

Let us look at the parts of the design of these pickups that define the sound.

The bridge pickup was originally designed for the Esquire. This guitar also had a 3 position switch. 1 position bypassed the tone control. 1 position engaged the tone control, and 1 position engaged a tone rolled off circuit ‘bass preset’ for the guitar to emulate a bass guitar. The bridge pickup has quite a tall shaped bobbin that the extremely thin (thinner than most pickups) wire is wound. Also, Alnico 5 magnets are quite strong magnets. These items all add to the cutting treble and snappy response of the bridge pickup in a similar way to that of the Stratocaster. The difference with a Telecaster bridge pickup comes mainly from a metal baseplate of the bottom of the bobbin and it being fitted into a metal bridge surround. These things combine to give the Telecaster bridge pickup its distinctive sound.

The neck pickup was settled on to be a darker more woolly, soft tone to contrast with the bridge pickup. A lot of this difference comes from the position of the mounting of the pickup (it being closer to the middle of the scale length) but also a considerable amount of the difference comes from the different shape of the coil and the metal cover.

Back to the history.



P90

After Les Paul had been kicked out of Gibson with a fly in his ear. Gibson considered the possibility in electrifying their acoustic / archtop guitars. The pickup they design came to be the P90 (in a few different design configurations.




Charlie Christian p90 pickups above. After this came the soapbar configuration, the dogear configuration and the staple version.



These are all very similar in design to all single coils but differ in 2 distinct ways. The bobbins of coiled wire are shorter, squatter units and the pole pieces, rather than being individual magnets in single coil pickups. In p90 pickups the pole pieces are ferric pieces of metal and are magnetised by a magnet attached to the bottom of these



As you can load the p90 up with more coil winds it tends to be a higher output pickup. The shorter, squatter bobbin gives a rounder, softer woollier sound. The original Gibson units used Alnico 5 magnets which also leads to giving the pickup more treble bite.

I realise some of these phrases I’m using are unscientific, difficult to imagine and pinpoint how the design affects the sound (see things I should expand on). Most of the original design was about achieving a sound and doing that as cheaply as possible and the shape and sound were not researched or designed. They electrified the guitar and had a desirable, marketable product. But there was a problem. These single coils and p90 pickups had/have a design fault. This design fault was intrinsic to the sound they produced so could not be designed out by normal research and development. For some players and in some situations the design would become an issue. The problem being mains hum (60 cycle USA or 50 cycle UK). Mains electric, particularly in the 50’s and particularly with some types of lighting induce a small voltage into the single coil and p90 pickups. This was more apparent in recording studios, with lots of fluorescent lighting and lots of electrical equipment.



Lover Man

Seth Lover an employee at Gibson decided to set about looking into this issue. I have struggled to find out detailed information about his humbucking pickup (to ‘buck’ the hum), but I can see that Electro voice had a similar invention that they used in public address systems, microphones and speakers. Arnold Lesti had a similar patent to the humbucking pickup. A.F. Knoblaugh invented a similar pickup that was used in Baldwin pianos. Also, in 1939 Radio Craft Magazine printed an article on how to make a similar pickup design to Seth Lover’s unit.



Seth Lover’s Humbucker was an impressive combination of these previous inventions but was different enough from them all for him to earn a separate patent. In 1955 these Patent Applied For or ‘PAF’ pickups entered the Gibson catalogue.




These were designed with 2 back-to-back bobbins wound to the same (or as close as the normally immigrant, low paid, low skilled, mainly women workers could do manually starting and stopping the winding machines) specifications. The being positioned so one bobbin has a magnetic polarity of North up and the other so the South pole is up. This is done so any noise or interference induced into the one coil is also induced into the other but the phase is reversed so the summed signal only allows the original signal through and the interference is phase cancelled. In a similar way to how a balanced cable works.


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