Audiogearreviews.com Glossary
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Glossary Category - Amplifiers
Amperage
The rate of flow of electricity through wire - measured in terms of amperes.
Ampere
The measurement of the flow of an electric current through a conductor.
Amplifier (Audio)
A device that increases the output level of the signal it receives without changing the sonic characteristics of that signal. While typically used to describe a device that drives speakers (transducers) it does define any device that increases the level of the audio input signal.
Amplitude
The measure of how powerful sound waves are in terms of pressure or voltage.
Analog
Continuously variable audio signal that can take on any value within a given range.
Attenuation
The process of weakening or reducing the amplitude of a audio signal.
Audio Bandwidth
The audible frequency range of human hearing
Battery (B-)
The ground terminal post of the battery.
Battery (B+)
The positive termial post of the battery. It also refers to the electrical connection that is always energized with 12 volts + from the battery.
Class A
Amplifier operation where both output devices conduct continuously for the entire cycle of signal swing, or the bias current flows in the output devices at all times. In class A operation, both upper and lower output devices are always on. Class A is the most inefficient of all power amplifier designs, averaging only around 20% amplifier efficiency.
Class AB
A combination of Class A and Class B operation that combines the efficiency of Class B with the reduced crossover distortion created by the transition between the upper and lower output devices. Typical good Class AB amplifiers average between 50-60% amplifier efficiency.
Class B
Amplifier operation where only the upper or lower output device is operating at one time.
Class B is more efficient than Class A but suffers from crossover distortion where the transition of the upper and lower output devices transition.
Class D
An amplifier configuration where the output devices are digitally controlled and pulsed on and off to generate the audio output signal. This is an extremely efficient design that averages 70-80% amplifier efficiency. The short fall is the difficulty in accurately producing high-frequency audio signals. As a result, most Class D amplifiers are designed for subwoofer use.
Class T
An proprietary amplifier configuration that operates digitally like Class D but switches at ultra-high frequency allowing for full range operation.
Crossover
An audio device that separates the audio signal into two or more bands for reproduction by different speakers
Crossover (Bandpass)
A device, circuit or algorithm that combines the functionality of a high-pass and low-pass crossovers to allows a band of frequencies to pass through while filtering (blocking) out frequency above and below the pass band.
Crossover (Electronic)
A crossover that separates the audio signal in the pre-amplifier stage. It can be a stand alone device or incorporated in an amplifier, signal processor or source unit.
Crossover (High-pass)
A device, circuit or algorithm that allows higher frequencies to pass while filtering out (blocking) lower frequencies.
Crossover (Low-pass)
A device, circuit or algorithm that allows lower frequencies to pass while filtering out (blocking) higher frequencies.
Crossover Point
The frequency point at which the crossover affects or filters the audio signal.
Current Draw
The amount of current of an electrical device from vehcile's electrical system.
Damping Factor
The ability of the amplifier to control the movement of a speaker (transducer). It is the ratio between the speaker's impedance and the output impedance of the amplifier.
Differential Inputs
An audio signal delivery system that reduces noise. For each input signal there are two signal wires. A third connector allows the signals to be referenced to ground. The audio output is the difference in voltage between the two wires: any voltage (noise) common to both wires is removed.
Digital Ready
A marketing term to make customers think that speakers and amplifiers are capable of dealing with the dynamics of a digital source.
Efficiency (Amplifier)
The ratio between the amounts of power consumed versus the amount of power produced. Efficiency depends on many factors, including but not limited to, battery voltage, amplifier load and impedance load of the speakers.
Frequency
Frequency is the measurement of the number of times that a repeated event occurs per unit time. In audio, it is the number of times a speaker oscillates (cycles) per second.
Gain
The ratio of the signal output of a system to the signal input of the system.
Gain Control
Adjustment device use to match the ouput of an audio device to the input sensitivity of another audio device.
Hertz (Hz)
The measurement unit of an audio frequency that is defined by the number of cycles per second. Can also be referred to as the pitch.
ILS Rating
This is the power rating technique used by manufacturers to misrepresent their products power output capability the term “ILS” refers to “If Lightning Strikes” In reality; all ratings that are not governed by the CEA-2006 standard should be carefully examined.
IM Distortion
Intermodulation Distortion. The ratio, in dB, of the total rms signal level of harmonic sum and difference distortion products, to the overall rms signal level.
Impedance
This is the total opposition to the current flow of an Alternating Current (AC) within a measured system. Measured in Ohms.
Input Sensitivity
The range (in volts or millivolts) that a electronic device is designed to accept.
Octave
The frequency bandwidth ranges defined by the interval of half or double of the starting frequency.
Ohms
The measurement unit that defines electrical resistance.
Phase (Out of)
When two audio signal do not sync exactly. This is a common occurance in car audio.
Polarity
The orientation of the positive and negative connections of an audio signal.
Polarity (Out of)
A situation when a two or more speakers are 180 degrees out of phase from eachother.
Power (Peak)
The peak power that either an amplifier can produce into a give impedance load or a speaker (transducer) can handle in its recommended frequency range.
Power (RMS)
The continuous power that either an amplifier can produce into a give impedance load or a speaker (transducer) can handle in its recommended frequency range.
Resistance
Electric resistance: a material's opposition to the flow of electric current. Measured in ohms.
Restitor
A device, with electrical resistance, that is used in an electrical circuit for current control and efficient operation.
Slew Rate
The maximum rate which an amplifier's output can change, generally expressed in V/µs. This is the speed of the amplifier.
Slope Rate (dB/Octave)
Is the rate at which a crossover attenuates or filters an audio signal.
Total Harmonic Distortion (THD)
The measurement of the distortion of a signal in the acoustic or analog domain. It is usually referred to THD + Noise.
Vapor Ware
Product displayed and introduced to the market that does not exist.
Volt
Basic unit of electrical potential. One volt is the force required to send one ampere of electrical current through a resistance of one ohm.
Xover
See Crossover
