USERS GUIDE TO PICKUPS

For something so simple - a bunch of wire wrapped around a magnet - pickups can have a huge impact on your sound. Unlike, say a pedal amp or pick, it's not really possible to try out a pickup within your existing rig. Variances in guitar scale length, construction, shape and material mean the same pickup will perform differently from guitar to guitar, so what works in a Telecaster may not work in a Les Paul and vice versa.

Essentialy, a pickup is made up of a magnet and insulated copper wire. It's the stuff of high school science: the magnet magnetises the strings, creating a flux field. When the string is struck, the vibration affects the flux field, creating an alternating current within the coils of wire. The signal is then sent to the amp, and a whole new set of techy stuff happens. The interesting and often confusing thing about pickup construction, it that different types of magnet and different guages of wire have different sonic characteristics. The size of the pickup also has an effect. The thinner the pickup, the thinner ther sound. This is why single coil sized versions of humbuckers dont sound quite the same - they're picking up the vibration of a smaller are of string. Pickups are typically made up of one of two types of magnet - Alnico or ceramic. Alnico is shorthand for "Aluminium, Nickel, Cobalt", and is an allow which has a softer magnetic field, and thus less pull against the strings. Alnico pickups are often associated with spongier tones, and players such as Slash. There are varying grades of Alnico magnet, each of which has its own sonic signature.

Ceramic magnets are a combination of magnetic iron and rare earth materials which are pressed into bars under pressure and heat. They're typically used in hotter sounding pickups with more distortion and harmonic content, such as the Dimarzio Evolution, or to beef up single coil sized humbuckers. When it comes to the wire coil, several factors influence the sound , including the number of turns, the pattern used - is it just wrapped around uniformly or criss crossed. - and the thickness of the wire. Matching the number of turns with a specific frequencies can be 'goosed' in a similar way to setting a wah pedal in a notch position. Pickups with this effect include the Dimarzio FRED and Tone Zone. The guage wire and the amount and style of turns have an effect on the pickup's DC current resistance. The higher the resistance, the lower the treble response and the higher the output.

A pickup's impedance also affects the frequency, and can be turned to certain frequencies to further emphasise upper mids or high end. A pickup's pole pieces also have an effect on the tone. The size, material and height of each pole piece can impose its own sonic signature.

Essentially, a humbucker consists of two single coils wired in series, but one uses a magnet of opposing polarity to the other. The hum characteristics of one coil are cancelled out by the other, hence the term 'humbucker'. On more modern strat style designs, the middle pickup is reverse winding and reverse polarity so it cancels hum when combined with the neck or bridge pickup.

Humbuckers tend to sound thicker and louder that single coils, but just to complicate things, they can be' tuned' to sound more like a strat style single coil or a Gibson style P-90. There are many other types of pickup - piezo, active, contact HEX - but that's for another coloumn.