A condition where the output signal is the same amplitude as the input signal; the overall system gain is then x1 or unity.

To play the same melody using two or more different instruments or voices.

A 2-wire electrical signal connection where the signal conductor is surrounded by a screen which provides a 0V reference and also guards against electrical interference.

The colloquial term to describe a loudspeaker drive unit optimised for the reproduction of high frequencies. (See Woofer).

see Valve

A metal bar within a guitar neck which is tensioned so as to counteract the tendency for the neck to bend under the tension of the strings.

– A form of digital audio meter which is capable of determining the absolute amplitude value of a digital signal by using oversampling to fully reconstruct the waveform.

TRS refers to the 3-terminal 'Tip, Ring and Sleeve' format of various types of jack plug, typically used either for stereo unbalanced connections (such as on headphones) or mono balanced connections (such as for line-level signals). A 2-terminal alternative is also available, referred to as the TS (Tip, Sleeve) version, used for mono unbalanced signals. The term is applicable to A-type, mini-jack, B-type, and Bantam connectors.

A symmetrical triangular shaped wave containing odd harmonics only, but with a lower harmonic content than the square wave.

An electrical device in which two or more separate and electrically isolated coils of wire are wound around a common ferromagnetic core. Alternating Current passing through one coil creates a varying magnetic field which induces a corresponding current in the other coil(s). In audio applications transformers are often used to convey a signal without a direct electrical connection, thus providing 'galvanic isolation' between the source and destination. Winding a transformer with different numbers of turns for each coil allows the output voltage to be increased or decreased in direct proportion – a feature widely employed in mains power-supply transformers to reduce the mains voltage to something more appropriate for the circuitry, for example, or in microphone preamp step-up transformers.