Dolby’s surround sound systems started with an analogue 4:2:4 phase-matrix system with a very elaborate active-steering decoder called ProLogic, before moving into the digital realm with Dolby Digital, Dolby Digital Plus, Dolby True HD, and others.

A manufacturer of analogue and digital audio equipment in the fields of tape noise-reduction systems and cinema and domestic surround-sound equipment. Dolby’s noise-reduction systems included types B, C and S for domestic and semi-professional machines, and types A and SR for professional machines. Recordings made using one of these systems must also be replayed via the same system. These systems varied in complexity and effectiveness, but essentially they all employed the principlals of spectral noise-masking in ever-more complex ways using multiband encode/decode processing to raise low-level signals during recording, while reversing the process during playback.

Direct Memory Access. Part of a computer operating system that allows peripheral devices to communicate directly with the computer memory without going via the central processor (CPU).

An abbreviation of Diskette, but now used to describe computer floppy, hard and removable data storage disks.

Used to describe vinyl discs, CDs and MiniDiscs.

A system whereby low-level noise equivalent to one quantising level is combined with a digitised audio signal in such a way as to perfectly linearise the digital system. Dither must be employed whenever the wordlength is reduced, otherwise quantising distortion errors will manifest.

A means of connecting two electrical circuits so that both AC and DC signals may be passed between them.

A form of audio compressor which uses a diode-bridge (sometimes known as a diode-ring) arrangement as the variable gain-reducing element. The design was popular in the 1960s as it provided faster responses than typical opto-compressors, and less distortion than many FET designs. However, noise can be an issue as the audio signal has to be attenuated heavily before the diode-bridge, and considerable (~40dB) gain added subsequently. The diodes also need to be closely matched to maintain low distortion.

A consumer multi-pin connection format used for vintage microphones, some consumer audio equipment, and MIDI cabling. Various pin configurations are available.

A digital processor which simulates acoustic reverberation.