AMS Neve Libra Live II Series User Manual page 90

Issue 4
System Operating Level
This defines the console operating level with respect to the maximum digital encoding level and in
effect sets the digital headroom to a value between 8dBu and 30dBu. The default is 18dBu.
Changing the operating level alters the level of the tone generator and changes the dynamic
processing threshold levels.
To change the operating level
Select a value in the 0dBu Equivalent To box.
Operating Level Notes
Digital levels are expressed relative to the maximum level before clipping starts. This is
0dBFS or 0dBFSD, meaning 0dB Full Scale (Digital).
The analogue level that 0dBFS translates to is set by the Analogue to Digital and Digital to
Analogue convertors independently of the console's operating level.
Choosing the Operating Level
Most broadcasters have house standards for the analogue level 0dBFS equates to and for the
operating level. In the UK 0dBFS is normally set at +18dBu and the operating level is set at
+4dBu. In Europe, 0dBFS is usually at +15dBu with an operating level of +6dBu and in the US
0dbFS usually equates to +20 dBu with an operating level of +4dBu. There are variations, but
even here there is a variation in headroom of 9dB in Europe and 16dB in the US.
In practice, input headroom will vary according to the type of signal. Digital sources such as CDs
are usually recorded at a high level with respect to 0dBFSD. Microphone sources with wide
dynamic range may have a nominal headroom in excess of 20dB. This input headroom variance
is accommodated by using a combination of analogue and digital gain trims.
The console tone generator is preset to produce a signal at the operating level +4dB when set to
0dB (to read '0' on an analogue meter set for an operating level of +4dBu). The dynamics
thresholds will be similarly normalised.
Example 1
Analogue convertors set for 0dBFS = +18dBu, Operating level set 0dBu =-18dBFS.
ADC clip level:
DAC clip level:
Console 0dB reference: -18dBFS
Meter zero:
0dB tone level:
Example 2
Analogue convertors set for 0dBFS = +24dBu, Operating level set 0dBu =-20dBFS. (Sony/US
convention)
ADC clip level:
DAC clip level:
Console 0dB reference: set to -20dBFS
Meter zero:
0dB tone level:
Example 3
Analogue convertors set for 0dBFS = +15dBu, Operating level set 0dBu =-15dBFS.
ADC clip level:
DAC clip level:
Console 0dB reference: set to -15dBFS
Meter zero:
0dB tone level:
+18dBu (Factory standard)
+18dBu (Factory standard)
+4 dBu
+4 dBu (reads 0 on meter)
set to +24dBu
set to +24dBu
+8dBu
+8dBu (reads 0 on meter)
set to +15dBu
set to +15dBu
+6dBu
+4dBu (reads -2dB on meter)
Libra Live Series II User Manual
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