Amplifiersa powerful beast

amplification

• amplification is the use of a small volatge/current to control a larger voltage/current. A change in the input is reflected a a proportional change in the output.

• the changing voltage/current is called the signal

• the amount of increase in output signal over input signal is called gain

line amplifiers• devices designed to increase signal

voltage

• most line amplifiers operate on standard signal level

• line amps isolate inputs and outputs and restore gain after signal processing

• amps that isolate sensitive portions are buffers and those that restore signal are boosters

unity-gain amplifiers

• purpose of the unity-gain amp is to relay signal without either increasing or decreasing its signal level

• unity-gain amplifiers are used as buffers and as the basic signal handling element in automatic gain control devices

preamplifiers

• is used to raise an extremely low-power signal to line level

• most transducers(phono pickups, microphones, tape heads) generate extremely low signal power

• preamps for mics are usually in the mixing console

• phono and tape require preamps located near the device

preamplifiers

• preamps are usually built into console, tape recorders, and other large pieces of audio equipment and rarely include any control

• exception is the variable gain control microphone preamp in mixing consoles

power amplifier• sole purpose is to boost a low-

voltage input signal, line level(.75 -1.0 volt) to a high-voltage output signal( power level)capable of efficiently driving a loudspeaker

• typically take a line level signal, power level of 3.3 milliwatts, and boost it to an output level of about 1 or 2 watts to as much as 100 to 200 watts

power amplifier• the power amplifier is very nearly a pure

current source highly susceptible to short circuits

• most amps have automatic power protection circuitry(parallel connections in speakers lowers impedance)

• damping factor to check ballistic nature of speakers, because the inertial movement of the cone acts a generator to produce counter emf in the circuit between the speaker and the amp

power amplifier• damping factor, the higher the

damping factor the more effective spurious signals are suppressed

• clipping occurs when the amplifier cannot produce a voltage output greater than the power supply then the waveform is flattened at the top or bottom. Clipping is a form of distortion that is particularly obnoxious