Linear Acoustic LQ-1000 User Guide
Troubleshooting
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5.1.2
The “LA” symbol is flashing red
The small Linear Acoustic logo in the upper right corner of the display is used to indicate
that the reference input is either missing or wildly incorrect. Check to make sure that an
AES signal is connected to Main Input 1 or that there is an SDI signal present, then make
sure the clock is set appropriately (see Chapter 4).
5.1.3
Output Audio Clicks and Pops
This could indicate that the chosen reference signal is missing or at the wrong sample rate
(the unit expects to be locked to 48kHz). The unit is designed to default to an internal
48kHz reference in case the external reference is removed. This allows audio to continue,
but due to the sample rate converters present on each input pair, the outputs will be asyn-
chronous with the inputs. The solution is to make sure that the reference is connected.
It could also mean that audio applied to the unit is not properly referenced, or that the
equipment that the LQ-1000 is feeding is not properly referenced. Using the master bypass
function of the unit is a helpful way to troubleshoot this issue.
5.1.4
Audio Sounds Strange
Reports of audio that sounds like it is in a tunnel indicate timing issues between the channel
pairs. Most often viewers watching in stereo will be the first to notice such problems. Off-
sets as small as a couple of milliseconds may quickly become audible under the right con-
ditions.
5.1.5
Audio Fixed by Re-boot
This can be a very misleading situation. Experience has shown that re-booting can some-
times fix things by interrupting the AES signals thereby causing equipment downstream to
re-lock to the incoming signals. This will sometimes mask the true problem. Careful and
methodical troubleshooting is essential, clocking issues can be tricky.
5.1.6
Audio Has Artifacts
Sometimes described as “squirrels in the surrounds” this is almost always caused by source
content that has been encoded at too low a rate. For example, some program delivery ser-
vices or server systems may use MPEG 1, Layer 2 audio data reduction to save bandwidth.
When operated at 256kbps or higher per stereo pair, there will be no issues. However,
128kbps or lower can result in coding artifacts that are present in the original stereo and
may be unmasked by when isolating channels. Note that this content is inferior in quality
and will have worse results if consumers matrix decode the signal (which is the default
mode for most home theatre A/V receivers fed with stereo). Our best advice is to take this
up with the program provider or server manufacturer. Today, bandwidth is cheap and
there is no good reason to run lower than 256kbps per channel pair at a minimum.
Summary of Contents for LQ-1000
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