29
Glossary of Terms
A/D
- An acronym for “Analog to Digital,” which refers to the conversion of analog signal to digital.
ADAT
- An acronym for “Alesis Digital Audio Tape.” ADAT was the name given to the Alesis-branded
products of the 1990s which recorded eight tracks of digital audio on a standard S-VHS video
cassette. The term now generally refers to the 8-channel optical connection that is used in a wide
range of digital products from many manufacturers.
AES
- (sometimes written as “AES/EBU”) The name of a digital audio transfer standard jointly
developed by the American-based Audio Engineering Society and the European Broadcast Union.
Designed to carry two channels of 16-, 20- or, 24-bit digital audio at sampling rates of up to 192kHz,
the most common AES physical interconnect utilizes a 3-conductor 110 ohm twisted pair cable,
terminating at standard XLR connectors. (See “Dual Wire” and “Single Wire”)
Analog
- Literally, an analog is a replica or representation of something. In audio signals, changes in
voltage are used to represent changes in acoustic sound pressure. Note that analog audio is a
continuous representation, as opposed to the quantized, or discrete “stepped” representation created
by digital devices. (See “Digital”)
Balanced
- Audio cabling that uses two twisted conductors enclosed in a single shield, thus allowing
relatively long cable runs with minimal signal loss and reduced induced noise such as hum.
Bit
- A contraction of the words “binary” and “digit,” a bit is a number used in a digital system, and it
can have only one of two values: 0 or 1. The number of bits in each sample determines the theoretical
maximum dynamic range of the audio data, regardless of sample rate being used. Each additional bit
adds approximately 6 dB to the dynamic range of the audio. In addition, the use of more bits helps
capture quieter signal more accurately. (See “Sample” and “Dynamic range”)
Bit Depth
- (See “Bit Resolution”)
Bit Resolution
- Used interchangeably with “bit depth,” this is a term used to describe the number of
bits used in a digital recording. The 4-710d converts analog audio and transmits digital audio with a
resolution of 24 bits (thus yielding a theoretical dynamic range of approximately 145 dB), the highest
resolution in common use today (dithered 16-bit output is also available). (See “Dynamic Range”)
BNC
- A bayonet-type coaxial connector often found on video and digital audio equipment, as well as
on test devices like oscilloscopes. In digital audio equipment, BNC connectors are normally used to
carry word clock signals between devices. BNC connectors are named for their type (Bayonet), and
their inventors, Paul Neil and Carl Concelman. (See “Word Clock”)
Class A
- A design technique used in electronic devices such that their active components are drawing
current and working throughout the full signal cycle, thus yielding a more linear response. This
increased linearity results in fewer harmonics generated, hence lower distortion in the output signal.
Condenser Microphone
- A microphone design that utilizes an electrically charged thin conductive
diaphragm stretched close to a metal disk called a backplate. Incoming sound pressure causes the
diaphragm to vibrate, in turn causing the capacitance to vary in a like manner, which causes a
variance in its output voltage. Condenser microphones tend to have excellent transient response but
require an external voltage source, most often in the form of 48 volts of “phantom power.”
Clock
- In digital audio or video, a clock serves as a timing reference for a system. Every digital device
must carry out specified numbers of operations per period of time and at a consistent speed in order
for the device to work properly. Digital audio devices such as the 4-710d normally have an internal
clock, and are also capable of locking to external clock routed from other digital devices. In order to
