Biamp LTR - Manual (Page 175)

System Design
161
To establish proper gain structure, the primary element is input gain. Each system input provides
adjustable Gain In (trim), with an associated Peak indicator. For best performance, increase gain
on a given input until the Peak indicator just begins to flash on normal signal content. The Peak
indicator first comes on with 6dB of headroom remaining (before clipping occurs). To provide
additional headroom (allowing for louder input signals), it is recommended that gain then be
reduced by 12dB (two 6dB decrements). To monitor system levels, Peak Meters should be
connected at strategic points in the signal path, including at the inputs. With gain settings as
described above, input meters should indicate peak levels between 6dB and 10dB on normal
signal content (14dB ~ 18dB of headroom). This will provide good signal-to-noise performance,
with a safety margin of available headroom.
Throughout the rest of the system, various components will include level adjustment capabilities
(faders). By default, these faders are typically at 0dB (unity gain). This is a very good setting for
most applications, and does not necessarily need to be changed. However, any of these faders
can be used for real-time level control (as described above). Of course, faders can be used to
‘mix’ multiple signals at differing levels (i.e. microphones at 0dB and music at -10dB). Faders can
also be used to compensate for gain reduction (Leveling, Comp/Limiting, etc.) which may have
occurred earlier in the signal path. Note: Floating Point DSPs allow this type of gain staging
without the danger of clipping distortion or the loss of data bits. As long as signal levels do not
exceed maximum at the inputs or outputs (A/D & D/A converters), extremely high and low level
signals can be tolerated without negative impact on quality. However, remember that some
system components do not function well without proper signal strength (as described previously).
Applications
Application Bulletin (.pdf) files are available on the NEXIA software CD-ROM. The associated
design (.NEX) files for these applications are also included, as example references.