A post I made on TGP today: There are two main types of noise that get transmitted in an electric guitar. Lets call them Hum and Buzz. We will define Hum as 60 cycle hum. This type of noise is magnetic in origin. It arises from the 60 cycle magnetic pulse associated with the 60 cycle electrical signal in power lines. Passive pickups sense this noise the same way they sense the fluctuations of the magnetized string. The only (practical) way to get rid of this noise is to incorporate some type of anti-polarity hum signal. This can be done with hum cancelling pickups, a dummy coil or noise antenna. Magnetic noise cant be shielded against, at least not effectively with the materials (and thicknesses) typically used to shield electric guitars. You can think of the hum field as a standing wave set up by the web of magnetic sources in the environment. Thats why it goes up and down as you reorient your self with respect to the field and go through the nodes and anti-nodes in the standing wave. Buzz is electrical interference from other sources. This source of noise is not defeated by hum-cancelling and can only be shielded against. Any type of shielding forms a capacitor when grounded in the electric guitar circuit. Added capacitance in the circuit causes signal degradation. The greater the distance between the plates in this added capacitor (i.e. the shield and the hot parts of the circuit), the less the added capacitance. Therefore, cavity shielding is generally the least heinous way to get rid of buzz. This type of noise is more like broadcast EMI, its not as directional as hum, and doesnt really change much as you reorient your position. Buzz can be exacerbated by problems in your loop, like bad ground connections or effects at a different ground potential than the amp, etc. In an unshielded guitar, some amount of buzz (especially when your hands are not on the strings) is normal and generally it goes with the output (i.e. inductance level) of your pickups. For instance youll notice itll be lower on the same guitar with two pickups in parallel versus one pickup. Hum is almost always the worst culprit, and most people are satisfied with their noise level if hum is eliminated. However, if you want to be dead quiet, you need to get rid of both.
Posted on: Fri, 26 Dec 2014 23:12:48 +0000