AJA FS2 - Manual (Page 51)

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51 FS2 Installation and Operation Manual — System Cabling
FS2 Audio Level
Choices—Pro or
Consumer, US or
EBU Since the FS2 handles both digital and analog audio and can convert between the
two, it provides analog and digital audio level settings in the front panel menus
and the remote web browser. Standard practice typically sets the maximum
audio level approximately 20 db above the operating (alignment) level, allowing
enough headroom to handle peaks without clipping. Because different countries
and equipment types use different operating and maximum levels, the FS2 has
several audio level settings. These settings allow you to set the relationship
between the analog and digital audio levels to accommodate the equipment and
audio operating standards you use.
The FS2 offers four settings shown in the following table. The analog audio levels
listed in the table are defined in reference to 0 dBFS (where FS = full scale), which
is the maximum level that can be represented digitally. Note that the test method
for these levels uses a 1kHz sine wave.
FS2 Audio Level Settings
FS2 Audio Setting Meaning
+24 dBu analog = 0 dBFS
maximum audio level SMPTE standard (US)
With digital audio at the maximum possible level (before
clipping), the expected analog audio input level is +24 dBu, and
the output is scaled to this level.
Typically, the US Standard Operating Level is +4 dBu analog or -
20 dBFS digital. The FS2 +24 dBu setting allows 20 dB of
headroom (+4 to +24 dBu) per the SMPTE RP-155 standard.
+18 dBu analog = 0 dBFS
maximum audio level EBU standard (EU)
With digital audio at the maximum possible level (before
clipping), the expected analog audio input level is +18 dBu, and
the output is scaled to this level.
Typically, the EU Alignment Level is 0dBu analog or -18 dBFS
digital. The FS2 +18 dBu setting allows 18 dB of headroom (
0
to +18 dBu ) per the EBU R68 standard.
+15 dBu analog = 0 dBFS
maximum audio level German standard
With digital audio at the maximum possible level (before
clipping), the expected analog audio input level is +15 dBu, and
the output is scaled to this level.
+12 dBu analog = 0 dBFS.
maximum audio level Consumer equipment
With digital audio at the maximum level (before clipping), the
analog audio input level is +12 dBu, and the output is scaled to
this level. These levels are provided for consumer equipment that
outputs lower audio levels than professional equipment.
Consumer audio units are often given in dBV, with +12.2dBu
equivalent to +10dBV. The standard operating level corresponds
to -10dBV (-7.8dBu). The FS2 +12dBu setting provides
approximately 20 dB of headroom (+10 to -10 dBV).