Heads Amps
Amp Head Fast Facts
It is very important to note that the quality of the power supply governs the efficiency of all subsequent links in the chain. No matter how good the rest of the circuitry, the amplifier’s performance will suffer if the power supply is sub-standard. At this preparatory stage, power taken from the AC mains is transformed to a higher voltage and rectified to DC current through valve or semi-conductor diodes. A network of resistors, capacitors and an inductor finally smoothes the direct current and supplies different voltages to the various amplification stages.
A Brief History of the Amplifier and Heads
An electric guitar relies on amplification to increase the signal generated by the pick-ups when the instrument is played. The guitar cannot be connected directly to a loud-speaker because it takes more energy to drive the moving parts of a speaker than the vibration of the strings can generate across the windings of the pick-up. Therefore, an amplifier has to be used. It takes electrical power from an external source (either mains or batteries) and uses the signal voltage derived from the guitar to control the delivery of that power to the speaker. The amplifier enables you to modify tone and volume, and to add qualities such as distortion and echo.
Many musicians think of amplification only in terms of power amplifiers used to drive loudspeakers. However, in the strict sense of the word, “amplifier” is equally applicable to many sound processing or “effects” devices usually referred to by other names – expanders, equalizers and limiters, for example. Therefore, with the exception of the terms “damping factor” and “power output”, all the information in this section which concerns amplifier specifications can be taken as applying equally to these other devices.
Amplifiers and heads operate in one of two ways – either by using valves or by using transistors. The processes differ, and so, to some extent, do the characteristics of the amplified sound. Amplifiers can be designed to reproduce the input signal (the original sound) at the output (the speaker) with a very high degree of precision. This is, essentially, the meaning of “high-fidelity”. Hi-fi amplification is a fundamental requirement for amplifying acoustic guitars, bass guitars (when clean sound and projection are required), most keyboard, string and wind instruments, and , in particular, the human voice. The best PA systems and studio monitors embody state-of-the-art high-fidelity sound technology.
Amplifiers can also be designed to provide a harmonic enrichment of the signals fed into them. Many electric guitarists use this quality in preference to true hi-fi sound since it is an important factor in creating their own distinctive sound. The effect can also be of use to some electric keyboard instruments, but it is generally inappropriate for most other instruments unless some special effect is sought.
Amplifiers combined with the speaker(s) in one cabinet
are known as combo amps. These are readily portable and easy to set up,
but in cases where more flexibility is required (such as the need to add
extra power) it is common practice to use separate amplifiers (“tops”
or “heads”) and speakers (“bottoms”). The units can either be stacked
on top of each other or the amplifier can be placed some way away from
the speakers in order to minimize damage from vibration.
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