2-6
Basic Operation
Lexicon
ROW 0 AUDIO
0.0 Input Source
The PCM 91 can use its own internal clock as a timing reference,
or it can reference an external clock source from the rear panel
S/PDIF or AES jacks. Use ADJUST to select Ext XLR (AES), Ext Coax
(S/PDIF), Int: 48kHz or Int: 44.1kHz. When either analog rate is
selected, the digital input is disabled. To process audio from the
digital input, you must select Ext.
When External clock is selected, and the PCM 91 detects valid
digital audio, the rate of the external word clock will be displayed
with a label indicating the digital audio format type: Prf
(Professional) or Cns (Consumer, also called S/PDIF).
The following types of errors are detected when the PCM 91 is set
to Ext:
• No Lock: The PCM 91, at some point, lost lock to the
incoming digital audio signal. Digital audio
input is muted.
• Out of Range: The sampling rate of the incoming audio
signal is outside of acceptable tolerance limits
of +4%. Digital audio input is muted.
• Non Audio: Indicates transmission of non-audio data, such
as from a CD ROM. Digital audio input is
muted.
• CRC: The error is reported, but incoming audio is
accepted.
Dig In Status
Pressing Load/✱ from Input Source will display the current digital
input status. This status display is continuously updated, acting as
a real-time monitor of the PCM 91 digital input. This display is
active even when the PCM 91 is set to Internal clock. Note that in
the case of an AES Pro format signal, "Emp:Yes" means either CCITT
or 50/15μs emphasis.
If valid digital audio is detected, the display will show the external
clock rate and format information, along with the status of the
Emphasis bit(s) in the incoming audio signal. If the PCM 91 has lost
lock, the display message will indicate "No Lock" and
parenthetically show the internal clock rate now in use.
Upon loss of lock, or reception of non-audio data, the PCM 91 will
mute the digital input and display the following messages when
Input Source or Dig In Status is selected:
When the PCM 91 is receiving valid digital audio, selecting Input Source will
display the input connector, audio format, and the rate of the incoming signal.
When digital clock is selected, any loss of lock detected in the
incoming digital audio, or reception of non-audio data will cause
the PCM 91 to immediately mute the digital input and switch to
internal clock at the sample rate of the last valid external signal. An
error message will be displayed if this occurs. The PCM 91 will
repeatedly try to establish lock, returning automatically to External
clock if and when lock is confirmed.
Audio ✱Input Source
0.0 Ext: XLR Prf 48
Audio ✱Input Source
0.0 Ext: Cns 48kHz
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