Computer display screen (See also Monitor).

Found in large mixing consoles. The fader levels of a number of separate channels assigned to the VCA group can be adjusted together by the VCA Group fader but without mixing their signals together. Usually referred to as a DCA Group in a digital console.

See VCA. VCA compressors tend to be fast-acting (at least in comparison to opto-compressors), a wide dynamic range, and low distortion.

Voltage Controlled Amplifier. An amplifier in which the gain (or attenuation) is controlled by an external DC voltage. VCA's are used in a wide range of audio and musical equipment, such as fader-automation systems in large format mixing consoles, audio compressors, and synthesizers.

An audio compressor that employs a valve (tube) as the variable audio attenuator. Mu is an engineering term for gain, so this is a variable-gain compressor. In essence, the side-chain signal continuously adjusts the bias o the valve to alter its gain appropriately. Vari-Mu compressors are fast and smooth, with low distortion.

Also known as a ‘tube’ in America. A thermionic device in which the current flowing between its anode and cathode terminals is controlled by the voltage applied to one or more control grid(s). Valves can be used as the active elements in amplifiers, and because the input impedance to the grid is extremely high they are ideal for use as an impedance converter in capacitor microphones. The modern solid-state equivalent is the Field Effect Transistor or FET.

The latest (2014) incarnation of a Universal Serial Bus interface, carrying bidirectional data at speeds of 10Gb/s. USB-C is not compatible with previous generations (USB 1.1, 2.0, 3.0, 3.1) as it has a very different 24-pin connector which is symmetrical and employed at both ends of a free cable, and all devices have the same socket. Power is optionally available over USB-C connections at 5V with a current capacity of either 1.5A (7.5W) or 3A (15W).

Universal Serial Bus. A computer interface standard introduced in 1996 to replace the previous standard serial and parallel ports more commonly used. The USB1.1 interface operated at up to 12Mb/s, but this was superseded in 2000 by USB2.0 which operates at up to 480Mb/s. Most USB interfaces can also provide a 5V power supply to connected devices. USB3.0 was launched in 2008 and is claimed to operate at rates up to 5Gb/s.

USB connectors can be indentified by having a blue insert in the Type-A sockets and the letters SS (SuperSpeed). The latest edition, USB3.1 (launched in 2013) offers transfer rates of 10Gb/s, approaching that of the first generation of Thunderbolt interfaces. Like earlier USB interfaces, the USB3 format provides a 5V power supply, but the current rating has been increased from USB2.0's 200mA (1.0 Watts) to 900mA (4.5 Watts), and sockets designated as charging sockets can manage 1500mA (7.5 Watts).

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.