ELECTRIC AVENUES
Jul 1, 2007 12:00 PM, By Doug Eisengrein
You may feel you've conquered and mastered many areas of electronic music's technical complexities — the difference between hard and soft knee compression, how many megabytes make up a terabyte, how much disk space a four-minute song recorded at 24 bits will occupy, memorizing most of your standard MIDI controller assignments. But do you know exactly what is happening when you plug something into that everyday wall outlet? What exactly are watts, amps and volts, and what are these various attributes of the core ingredient of your studio — electricity? It's time to put on your pinwheel beanies and pocket protectors while we review some high-school physics and history basics.
W, A, J, V, Z…HANGMAN
It should be said right now that a single page is not enough space to explain in detail how electricity and currents work, much less illustrate all of the dizzying amounts of mathematical equations involved that can make your brain melt after a while. I'll cover just the most basic terms and concepts and, eventually, how it all relates to music.
Simply stated, electricity is a basic form of energy, like light, heat and, of course, sound. Power can be most simply defined as an amount of work done over time by an electric current. The basic unit of power is the watt (symbol = W), named for the Scottish engineer James Watt, who is noted for his many improvements upon the steam engine that helped usher in the Industrial Revolution. One watt is equal to one joule per second, with joules also representing a basic unit of “work done” or “work required.” The joule (symbol = J) is named after the noted 19th-century English physicist James Prescott Joule, who discovered the direct relationship of heat to mechanical work. Current, on the other hand, is an expression for the movement — or flow — of an electric charge. The basic unit of current is the ampere, or “amp” (symbol = A), and is equal to one coulomb per second. The coulomb is the basic unit of electric charge and, some say, is a more elemental electrical unit than the ampere. Ampere comes from the early 19th-century French physicist André-Marie Ampère, famous for his early discoveries in electromagnetism. The coulomb was so named for an 18th-century French physicist, Charles-Augustin de Coulomb, who published many famous papers dealing with the laws of attraction and repulsion also in relation to electromagnetism.
SINGLE VOLT SEEKS LONG-TERM RELATIONSHIP
Now here is where it begins to get more complex: Voltage is a measurement of the potential difference across a conductor (a copper wire, for instance). “Potential difference” is a term used in physics to describe an amount of energy required to move an object (in this case, a unit of electrical charge) from point A to point B against various forces. The volt (symbol = V) is named after the Italian physicist Alessandro Volta, who is credited with the creation of the Voltaic pile, or early electric battery. Understanding the volt itself is not more complex than that of amps, joules or watts; rather, it is here where we can begin to see how the different basic units in electricity are in fact a network of relationships. For example, volts equal watts divided by amperes; alternatively, watts equal volts multiplied by amps. I won't go into the tedious details of all equations here, but suffice it to say that basic units of electricity are relational, not necessarily separate from one another — kind of similar to the relationship of the Moon's gravitational pull on the Earth's oceans.
OOOHHHHHMMMMMM…
Another fundamental aspect to electrical power is resistance (symbol = R). Also known as impedance (often expressed as Z, as in “hi-Z” or “low-Z” audio inputs or mics) in the case of electrical circuits, resistance is rated in ohms (symbol = Ω). The ohm is so named for the German-born mathematician and physicist, Georg Simon Ohm, who was responsible for first explaining the basic relationships underlying current, voltage and resistance. Curiously, in his early studies, Ohm made use of a version of the recently invented (at that time) Voltaic pile, exemplifying the network of relationships found even among the inventors themselves.
In a nutshell, when applied to a circuit, resistance can have the result of dissipating a certain amount of power (in watts). Strong resistance applied to circuits can also have the desired (or not-so-desired) effect of converting the energy into several other forms, such as light, sound or heat. Understanding resistance is one of the more difficult yet crucial aspects for musicians and engineers to understand because it is encountered in many places and needs to be handled appropriately. For example, it is very bad practice to connect a Hi-Z source to a Low-Z input. Or, when purchasing a power amp to drive your band's PA speakers, never listen to a salesperson who only tells you, “Check it out: This is a 3,000W amp!” You'll need to know how many watts it can push into four, eight and 16 ohms — in stereo or bridged mode. I'm sorry, did you think that your 3,000W beauty could power two speakers the same as it can 12? Think again. You'll need to call on your soon-to-be prodigious knowledge of electrical relationships in situations like that.
DON'T PLAY HOOKY
I will leave you with some recommended reading on this topic. Basic Electricity (REA, 2003) by Max Fogiel, which covers the nuts-and-bolts of electricity in depth, is a good book for the more geeky, “I've gotta know how this works!” crowd, while the ubiquitous Sound Reinforcement Handbook (Yamaha, 1988) by Gary Davis and Ralph Jones is a biblical-like reference book that every engineer should own. This classic volume covers electricity basics as they relate specifically to sound systems. This is where you'll find proper answers to the dilemma of just how many 3,000W amps you need to buy if your band really does haul around 12 speakers from venue to venue.
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