The Incoherant Ramblings of a Poetic Compulsive: Instructional: Guitar Technology for Dummies

I had to write a quick synopsis on guitar technology for my lead singer awhile back. Thought it interesting so I thought I'd post it.

This is a brief document outlining some of the terminology and common concepts utilized in the technology used in regards to the invention of the electrical guitar and its amplifiers. Hopefully, this is most everything you’ll need to hold a brief, but intelligent conversation with someone should the occasion arise. I’ll try not to get too heavy into the acoustic-electric physics.

Basics
Watts. A watt is a unit of electrical power (technically it’s current times voltage [Watt’s Law]). 1dB (or decibel) is the threshold of perceiving an increase in volume. 3dB isn’t much, but it takes twice as much power to increase in volume by 3dB. It takes 10x the power to get a doubling of the dB (volume). For example if you can produce 100dB of sound with 30 watts, to increase to 200dB would take 300 watts (or 300W). Solid State is a term referring to newer amps that use electrical systems that involve transistors and IC’s (integrated circuits or “chips”). Solid State is slang for “digital” essentially. Amps made prior to the late 70’s are not solid state. Older amps use electrical systems comprised of vacuum tubes or “tubes” for short instead of IC’s and transistors. These electrical systems are referred to as “analog”. Tubes are utilized specifically in the circuits responsible for shaping the tonal qualities that will be sent to the speakers. Newer amps can also utilize tubes, though they are considered higher end amps and usually will have integrated circuits and/or transistors in the components inside the amplifier not directly responsible for the tonal aspects and quality.

Amplifiers
Every amplifier consists of 3 things: a preamp, a power amp, and a speaker cabinet. The “preamp” is responsible for conditioning the sound. Your equalization is in your preamp. Equalization of course is the level of presence of various frequencies. The frequencies of concern for an electric guitar are generally between 100 and 6,400 Hertz (abbreviated Hz). The frequencies in question for a bass guitar are typically between 40 and 4,500Hz (though bass equalization will sometimes go as high as 10,000Hz – this for slapping mostly and as low as 30Hz which is only a subharmonic). The “power amp” is responsible for boosting the signal to a degree that the signal is audible when sent to a speaker or set of speakers. Both preamps and power amps can be either solid state or tube driven. If an amp has a tube preamp but a solid state power amp it is said to be a hybrid. These are fairly new Frankensteins and many swear they sound better than a solid state. Power amps for the electric guitar are rated as low as 10W and as high as 400W. Most of the guys playing guitar in stage-sharing bands that we’ll come across will be using 50W to 200W at most. There are only really a few amps that produce more output than 200W and they’re quite expensive typically. Bass amps however, range in power from 100W to 2000W. Most of the bands we’ll play with will likely have bass amps rated for 250W to 800W. Mike Adams’ cab was rated for 1200 or 1600. It was quite overkill for us. Speaker Cabinets are of course the enclosure, or box, that contain the speakers. Speaker cabs are rated to accept a maximum wattage from a power amp. To exceed this wattage is very dangerous and will usually damage the speakers. In some amps, such as yours and mine (currently) the enclosures are part of the same construct as the preamp and power amp. Amps that house all three of these components (like yours and mine) are referred to as Combo Amps. Other amps, like Andrew’s and Mike Adams’ the preamp and power amp are in one construct and you connect a cable (or two if stereo) to the speaker cabinet. The housing for the preamp and power amp is affectionately referred to as a head. Note that the cables connecting a guitar to an amp are NOT the same as the cables that connect a power amp to a speaker cabinet. Those cables are called speaker cables and should never be confused with instrument cables. These concepts regarding the preamp, power amp and speaker cab also apply to sound reinforcement gear (PA equipment), though the use of tubes is generally considered to be less important of a debate. Many amplifiers have two additional ports on them that make up what is called an effects loop. Sometimes it is not labeled as that, instead the ports are labeled as “Send” and “Return”. On other amps the ports are labeled “Pre Out” and “Power In”. What these two ports do is separate the preamp and the power amp allowing the guitarist to put other devices in between the conditioned signal and the power stage. This is handy mostly for effect pedals, thus the term “effects loop”.

There are essentially 4 types of amplifiers. Two of them you already have read about: solid state and tube. These are the two most popular types. A third type that is gaining more and more in popularity are modeling amps. Jon’s guitar amp (the Line 6 Spider) was a modeling amp. Modeling amps, in their most basic definition are solid state. I’ve never seen one that was tube and probably never will (maybe a hybrid at best). What makes a modeling amp unique to its own category is they have an array of different tones they can produce, and each tone has been designed to sound like a classic, vintage, or widely sought-after & appreciated amplifier model. The Pod and the Bass Pod are modeling preamps. These amps often contain a wide assortment of onboard modulation effects, delays, etc. We’ll cover effects later.

The fourth type of amplifier is called a rectifier. Some amps, most popularly Mesa Boogies, use what is called a rectifier to assist in the tonal production. It’s essentially another stage within the power amp that converts AC to DC before sending it to the speakers. It creates a unique tonal quality that is highly coveted in some circles. The rectifiers themselves can exist in either in tube form or in solid state form but typically are only used on higher end tube-driven amplifiers. I really don’t know much about how they work but I can pick one out of a crowd without a problem generally. They have a pretty unique sound.

Guitars
This will be a much shorter chapter than the one on amplifiers. Guitars are quite simple by comparison. Every electric guitar has three things that are different from an acoustic. An output jack, pickups, and control knobs. Very simple. The output jack is simply where the cable goes in to connect the guitar to the amp. The control knobs are just that. Typically an electric guitar will have at least two. Volume and Tone. Volume is self-explanatory. Tone, generally increases the amount of treble and presence the higher you turn it. It’s hard to explain the audible differences. The best way to really learn what a tone control knob does is to hear it. Some guitars have additional knobs for additional parameters or to turn on/off onboard features of a guitar. There’s hundreds of possibilities so I won’t explore every one, needless to say knobs that are not well-labeled on a guitar should not be played with too much if you don’t know what you’re doing (especially if it’s not your guitar). J Anyway, now to pickups. Single coil pickups are a series of 6 magnetic polls, targeted directly at the strings of the guitar. The magnets pick up the vibrations of the strings and create an electrical signal that is then sent to the amplifier. Humbuckers are a single pickup, but they look like 2 put closely together. There are 12 magnetic polls instead of 6. The additional set of magnets in parallel produce a hum-canceling effect, thus the name “humbucker”. They also produce a much louder and stronger tone (more polls equals hotter signal). Some guitars are built with a switch making a humbucker a single coil pickup when you flip it. That switch is called a coil tap.

Well, I hope that helps some. If you want to know anything else more specifically shoot me an email and I’ll be happy to answer any questions I can.

Bazooka-Joe made it so at 10:01 AM

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Monday, August 01, 2005

Instructional: Guitar Technology for Dummies

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