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Entries found for search: amplifier

amplifier gain : The amount of amplification that an amplifier provides is called its gain. The gain is a ratio of the input signal level to the output signal level and is simply a number. Commonly expressed in dBindB, one should not express the voltage gain of an amplifier in dBindB unless the input and output impedances are matched as the gain of a typical amplifier is not related to its power output capability. For instance, if an amplifier has a voltage gain of 10, it might be said that it has a gain of 20dB because it actually would raise the power level of a signal by 20dB if the input and output impedances were matched. In practice, however, this is very seldom the case, and the true power gain is usually very much different from what would be predicted by the voltage gain. See impedance matching.

amplifier : An electrical circuit or device designed to increase the current, voltage, or power of an applied signal. An amplifier is an active device and, strictly speaking, should always increase the power of a signal; some amplifiers, such as certain distribution amplifiers, may only reduce the impedance level of the signal for the purpose of driving long lines.

combining amplifier : An amplifier, also called a summing amplifier, that combines two or more signals prior to sending them to a single audio bus, signal processor, tape recorder track, or other destination. For example, on a mixer ifthean aux send controls on all channels of a console feed a combining amplifier, whose output can be routed to a reverb system, cue or headphone amp, the monitor amplifier, etc. There are also devices which are active combining amplifiers, called an ACA, as well as passive combining networks,

integrated amplifier : A consumer audio component consisting of a preamp and power amp all in one chassis.

inverting amplifier : See differential amplifier.

line amplifier : Any amplifier with a line-level output and an output impedance of approximately 600 ohms.

microphone preamplifier : See preamplifier.

summing amplifier : A circuit or device that combines or mixes signals from several sources, then amplifies the resulting mix for routing to another device. For example, if an aux send controls on all channels of a console feed a summing amp, whose output can be routed to a reverb system, cue or headphone amp, the monitor amp., etc. A mixer can be thought of as a type of summing amplifier. See combining amplifier.

preamplifier : (1) In an audio system, the first amplifier to accept the signal from the transducer is generally called a preamplifier. Preamps must usually accept very low-level, e.g., mic-level, signals and amplify them to line-level without adding appreciable noise. (2) A small amplifier built into a condenser microphone to boost the very low output level of the capsule before transmission over the mic cable.

power amplifier : A device n amplifier that accepts a low-level audio signal and strengthens, or amplifies, it to a suitable voltage and current level adequate to drive a loudspeaker or similar load. The four key parts of a power amplifier are the input stage (voltage gain), driver stage (phase splitting), output stage (load response), and power supply. See preamplifier, active, differential amplifier, integrated amplifier, combining amplifier.

voltage-controlled amplifier : See VCA.

differential amplifier : Usually one of the signal input terminals of an amplifier is connected to the chassis of the amplifier, i.e., it is grounded. The amplifier is then sensitive to the voltage difference between the input terminal and ground. However, in a differential amplifier, neither input terminal is grounded. Instead, the amplifier is sensitive to the voltage difference between the two inputs. Used in professional microphone preamplifier where a low-level signal has to go some distance, a differential amplifier cancels the hum induced by the proximity of the two input wires to a source of interference. In the UK, a differential amplifier is called an inverting amplifier. See differential input, common mode.

digitally controlled amplifier : See DCA.

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