Instruction Manual for LA4 with 1.0.X Firmware ā REV A Page 26
Audio Line Inputs
The LA4 features two stereo balanced XLR
analog inputs and two stereo unbalanced RCA
analog inputs.
Balanced XLR Interfaces
Balanced interfaces use higher signal levels
and for this reason, they provide better signal
to noise ratios. Balanced interfaces also
provide immunity from ground loop induced
hum and buzz. In general, balanced
interfaces are vastly superior to unbalanced.
Select products with balanced interfaces and
avoid the use of unbalanced interfaces
whenever possible.
Unbalanced RCA Interfaces
Given the widespread consumer use of
unbalanced RCA interconnects, we have made
every effort to extract the highest possible
performance from these antiquated consumer
audio interconnects.
The unbalanced RCA inputs on the LA4 are
connected to balanced receivers. These
balanced receivers provide significant
immunity to ground loop induced hum and
buzz. This topology provides the RCA inputs
with some of the advantages of fully-balanced
interfaces. Nevertheless, unbalanced
interfaces can never match the full
performance of professional-grade balanced
interfaces.
If your D/A converter and/or power amplifier
lack balanced interfaces, it is a good
indication that these devices are not true
high-resolution audio products. Look for
professional-grade balanced interfaces that
support 24 dBu signal levels.
Input Level Matching
By default, the unbalanced inputs on the LA4
are automatically boosted by 15.8 dB so that
they will match the level of the professional-
grade balanced inputs. If the 15.8 dB default
boost doesn't work in your system, individual
inputs can be trimmed by +/- 10 dB in 0.5 dB
steps using the BOOST function. The boost
value does not impact the audio performance.
It is equivalent to automatically rotating the
volume control when the input is changed.
The boost value changes the way the volume
is numerically displayed.
Tip: We recommend using professional-grade
balanced XLR interconnects that provide +24
dBu at 0 dBFS. Consumer-grade balanced
XLR interconnects operate at levels that are
about 10 dB lower (4 Vrms or +14.2 dBu at 0
dBFS). Consumer RCA interconnects operate
at levels that are about 16 dB lower (2 Vrms
or 8.2 dBu at 0 dBFS). High signal levels and
differential signaling are essential in high-
resolution audio systems. RCA interconnects
will limit system performance.
Audio Line Outputs
The LA4 features a stereo pair of balanced
XLR outputs and a stereo pair of unbalanced
RCA outputs. It also includes a balanced
mono sum output. The mono sum can be
used to drive a powered subwoofer.
The balanced outputs are designed to operate
at professional levels (+24 dBu at 0 dBFS).
The unbalanced outputs are designed to
operate at consumer levels (2 Vrms at 0
dBFS).
Unity Gain at 0 dB
If the volume control is set to 0 dB, the XLR
output levels will be identical to the XLR input
levels feeding the system. Likewise, the RCA
output levels will be identical to the RCA input
levels feeding the system.
15.8 dB Offset Balanced vs.
Unbalanced
Balanced outputs are 15.8 dB hotter than the
unbalanced outputs. Balanced inputs are
assumed to be 15.8 dB hotter than
unbalanced.
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