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The Magnetic Pickup
The guitar pickup revolutionised modern music as it brought us the affordable electric guitar, a pioneering instrument that has changed the shape of music in the 20th and 21st centuries. Essentially a pickup works to transmit the mechanical vibrations of the guitar strings into an electrical signal that can then be amplified when connected to suitable equipment. The basic pickup is rather simply designed and this has not changed since it was first invented, a permanent magnet is wrapped in a coil of copper wire. This coil consists of thousands of turns of wire and this helps complete the magnetic circuit. When the guitar is played the vibrations of the strings cause a magnetic disturbance and the pickups transmit this as varying voltages (usually between 100 mV to 1 V) to the amplifier. Even with standard guitar pickups there is a tremendous variety to choose from, each with varying amounts of copper wire and varying strengths of magnet in the design.
Higher output pickups as favoured by rock and metal musicians tend to utilise stronger magnets as these provide a stronger magnetic field for the strings to vibrate in, others use more turns of wire to increase the voltage to the amplifier. All of these variations result in pickups that sound noticeably different depending on how they are played, even things such as the type of magnet and the quality of the wire can affect the sound that is output through the amplifier. It is important to note that guitar pickups can be both "active" and "passive". The vast majority are passive as they simply sit and transmit the string vibrations to the amplifier, however active varieties are becoming more popular as they feature electronic circuitry in between the pickup and the amplifier that works to modify the signal. Usually active picks utilise a 9 V battery as a power source and because they are powered at the guitar they can feature things such as a premap, filters, equaliser and other features that help you adjust the tonal qualities of your guitar.
The main advantage of active guitar pickups is that the signal will not decay as much if long lengths of guitar cable are used. For stage performers this can be an important consideration, especially on bass guitars due to their much stronger tone. Obviously active guitar pickups can prove to be "louder" than their passive counterparts, however critics of active guitar pickups consider them tonally inferior to passives. Active pickups also produce much less hum than their standard counterparts, although this is subjective and depends largely on the quality of the pickup, amongst other things.
Click here to learn more about double coil or "humbucker" pickups.
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