Installation guide

TDM Installation Guide28
In expanded Pro Tools systems, the Super Clock
output of the master audio interface locks all
other interfaces together with sample accuracy,
keeping all signals phase-synchronous.
Ch 1–2 Input
This LED indicates the format (analog or digital)
of the audio input signal to channels 1 and 2. In
Pro Tools, you choose analog or digital input for
these two channels in the Session Setup win-
dow. Input channels 3 through 8 of the
882/20 I/O are always analog.
Sample Rate
These LEDs display the current sample rate of
the 882/20 I/O internal crystal oscillator, which
can be either 44.1 kHz or 48 kHz. In Pro Tools,
this is set in the Session Setup window.
The 882/20 I/O provides the following sample
rates:
48 kHz This is a standard sampling rate of many
professional audio devices. It is recommended
for use with devices that cannot receive digital
transfers at 44.1 kHz.
44.1 kHz This is the compact disc standard sam-
pling rate and the Pro Tools default sample rate.
To avoid the need for sample rate conversion,
you should use this rate when you are recording
material that will ultimately be published on a
compact disc.
Signal Present LEDs
These LEDs indicate whether signal is present
(above the level of –30 dB) at a given channel’s
output. These LEDs indicate the presence of
channel output signals, not input signals. Input
signals are monitored on-screen in the Pro Tools
software. The LEDs do not indicate clipping.
Clipping is indicated by the on-screen meters in
Pro Tools software.
882/20 I/O Back Panel
The 882/20 I/O has the following back panel
connectors, moving from left to right:
Analog Audio Inputs
These are balanced, 1/4-inch TRS jacks for ana-
log audio input connections. The 882/20 I/O
analog inputs feature 20-bit analog-to-digital
converters.
Input operating levels are switchable between
+4 dBu and –10 dBV operation. Unbalanced
connections are supported through the use of
standard 1/4-inch TRS mono phone plugs.
When slaving to a Digidesign Universal
Slave Driver, Video Slave Driver, or SMPTE
Slave Driver, set the clock source to Internal.
The audio interface will automatically
switch to Slave mode when it detects the
256x input clock.
When you are using an external digital
source such as a DAT recorder, the front
panel of the 882/20 I/O indicates only the
internal oscillator sample rate, not that of
the external digital source.
Back panel of the Digidesign 882/20 I/O
Analog
Inputs
Analog
Outputs
Slave
Clock
In/Out
S/PDIF
I/O
Power
50-pin
Interface
TDM_Install.book Page 28 Saturday, January 13, 2001 9:35 PM