25-Seven Systems program delay manager, Руководство оператора

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25-Seven Program Delay Manager Version 2.3 Manual April 2013 21
Select a value between
+20dBu
and -
10dBu
to result in fullscale within PDM and on the
digital output.
The bottom line of the display shows current Left and Right internal levels in dBFS. This
is the result of the incoming analog signal, adjusted by the second line of the LCD and
sent to the analog-to-digital converter. Typically, these should read –12 for a +4 dBu
lineup tone
1 .
For most installations, where 0 VU = +4 dBu, we recommend setting the analog
Input
sensitivity
to
+14dBu=0dBFS.
Analog
Output Level
Shown when analog or digital inputs are selected. The
LCD will look like this:
Output Level
0DBFS=+14dBu
““‘‘ Chg Value OK
L:
-
70 R:
-
70 CNCL
This shows how the analog output level reflects digital audio levels within
PDM’s processor. In this example, 0 dBFS inside PDM will cause a +14
dBu analog output. This particular setting is equivalent to the “0 VU =
+4 dBu” standard, with 10 dB of headroom.
Precise Left and Right output levels are displayed in dBFS
Select a value between -
10dBu
and
+20dBu
to appear at the analog outputs, when
PDM’s internal digital signal level is 0 dBFS. This is usually set to match the Analog In-
put sensitivity, so our recommendation for most facilities would be
0dBFS = +14dBu
.
However, you can use other settings if you want PDM to also create analog audio gain
or loss. Note that during Bypass mode, any such gain or loss is also bypassed: the out-
put equals the input.
The analog outputs are always active, even if a digital input has been selected.
Don’’t confuse dBu——an analog measurement——with digital dBFS!
Analog dBu is a comparison to an arbitrary voltage (.775 v), and signals can be much
hotter. A console’’s output is typ4 dBu (1.228 v) when the meter reads 0 VU,
but that’’s for a sinewave test signal. Peaks in voice waveforms, in real-world broad-
casting, can sometimes be considerably above that... even though properly-calibrated
VU meters are deliberately too slow to register them. Analog is very forgiving of
these momentary peaks.
However, in the digital world, 0 dBFS (decibels referred to Full
Scale) is an absolute ceiling. Some devices distort horribly or crackle
when an input attempts to pass this value. PDM handles overloads
differently, applying serious limiting to gracefully protect your signal
(and listeners).
1
The +14 dBu sensitivity in the figure would make these meters read –10 dBFS with a st4 dBu
line level test signal. In other words, the setting means a +14 dBu signal would read 0 dBFS—the maxi-
mum allowable digital signal—and standard line level is 10 dB less than that, or –10 dBFS.