About Digital Audio Formats And Format Conversion; About Surelock - Apogee BIG BEN User Manual

About Digital Audio Formats and Format Conversion

AES Single Wire or Double Fast or
Single Wide
AES Double Wire or Double Wide
S/PDIF Coaxial
S/PDIF Optical
FIGURE 6
As sample rates and bit resolutions have increased, digital audio formats have been
modified to handle the increased flow of data, to the point where the proliferation of
format variations has led to some confusion. For example, 5 variations of the AES/EBU
format have been developed to handle sample rates between 44.1kHz and 192kHz.
FIGURE 6 depicts the characteristics of the digital audio formats available on Big Ben,
including the names by which the format is known, the connector used, valid sample
rates, the number of digital audio channels per connection, and the rate of transmission.
For example, AES Double Wire format can carry only 1 channel of audio per connection,
uses XLR connectors, is used only with sample rates between 88.2 and 192 kHz, and
transmits data at half the sample rate – i.e., bits travel at 48kHz when transmitting a
96kHz digital audio signal.
To convert a digital audio signal from one format to any other format, the source format
must be selected as the CLOCK SOURCE. Digital audio data present at the selected
input will be routed to all outputs capable of transmitting digital audio data.
When format converting, Big Ben will transmit as many channels as possible based on
the input format selected and the capability of each output format. For example, if S/MUX
2 input (capable of accepting 4 channels) is selected as the CLOCK SOURCE and AES
is set to SINGLE (thus allowing transmission of 2 channels on each connector), S/MUX
input channels 1 & 2 will be routed to AES Output 1, while S/MUX input channels 3 & 4
will be routed to AES Output 2; on the other hand, only S/MUX channels 1 & 2 will be
routed to the S/PDIF Coaxial output (capable of transmitting 2 channels on the sole
S/PDIF connector).

About SureLock

Thanks to SureLock, Apogee's intelligent clock continuity algorithm, even the loss of the
input reference will not degrade the stability of Big Ben's outputs. When the selected
CLOCK SOURCE is no longer applied to Big Ben, the unit will continue to generate
clock outputs at the last known valid frequency; the "Wide" arrow will blink to indicate the
loss of the input reference while the blue "Narrow LED will light solidly to indicate stable
output. When an input reference is re-connected, Big Ben will attempt to regain lock as
seamlessly as possible; nonetheless, it's recommended to re-connect the input reference
at a moment when a brief interruption of Big Ben's output won't pose a problem.
Name(s) Connector used
XLR
XLR
RCA (coaxial)
Toslink (optical)
ADAT Toslink (optical)
S/MUX 2 Toslink (optical)
S/MUX 4 Toslink (optical)
Channels per
Valid Sample Rates
connector
44.1-192kHz
88.2-192 kHz
44.1-192kHz
44.1-96kHz
44.1-48kHz
88.2-96kHz
176.4-192kHz
BIG BEN – User's Guide
Digital Data Rate
2 Fs x 1
1 Fs /2
2 Fs x 1
2 Fs x 1
8 Fs x 1
4 Fs /2
2 Fs /4
APOGEE ELECTRONICS
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