M-AUDIO Super DAC - Manual (Page 8)

OPERATION
The SUPER DAC 2496 is compatible with 24-bit, 20-bit, 18-bit, and 16-bit data.
The more bits per data word, the better the dynamic range. Better dynamic
range translates into higher audio quality.
The term "sampling rate" means the number of times that digital audio takes a
"picture" of the analog signal. The more times per second you take a picture of
the analog signal, the more accurate the digital representation is. Therefore,
higher sample rates equate to better audio quality. Whichever sampling rate
you send to the Super DAC, from 22 kHz to 100 kHz, the Super DAC
automatically detects the sample rate and synchronizes to it. Once locked to
the sample rate, the front panel "Data Valid" LED will light.
The Super DAC has three digital inputs. AES/EBU is regarded as a
professional digital transmission protocol. Utilizing a three-conductor
balanced "XLR" type cable, this transmission method is considered the most
stable and runs the longest distances. S/PDIF and TOSLINK are essentially the
same transmission protocol, one using a two-conductor "coaxial" cable with
RCA connectors as the standard and the other a special "TOSLINK" type
optical cable. S/PDIF and TOSLINK are used in many professional situations
but are much more common in consumer equipment.
The front panel Format pushbutton selects the digital input that will feed the
D/A converter. Only one digital input may be selected at a time. When the
Super DAC recognizes valid data at the selected input, it decodes it to and
converts it to stereo audio which goes to the internal output amplifiers that
drive the balanced and unbalanced analog outputs.
The Super DAC balanced XLR outputs carry a professional-level audio signal
(+4 dBu nominally) across a pair of conductors surrounded by a ground shield
conductor. The two signal conductors are opposite polarity from each other
and at the receiving end are subtracted from each other. This results in a signal
that is twice as hot. More importantly though, any noise that is common to
both signal conductors gets cancelled during the subtraction! This makes
balanced signals more noise-immune than unbalanced signals. The noise
immunity and "voltage doubling" help to make balanced signals run further
distances than unbalanced ones.
The Super DAC 1⁄4” unbalanced outputs carry a consumer-level audio signal (-
10 dBV nominally) across a single conductor surrounded by a ground shield
conductor. Most consumer equipment operates with unbalanced connections.
Although by definition not as quiet as the balanced signals, the unbalanced
signals are still extremely quiet when used in a properly grounded system with
short cable runs.
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