Linear Acoustic AERO.ASI User Manual page 42

Linear Acoustic AERO.ASI User Guide Troubleshooting
Audio sounds strange
Reverberant audio that sounds like a tunnel indicates timing differentials between the channel pairs.
Stereo viewers are usually the first to notice such problems. The delay settings in AERO.ASI should
all be equal, or set explicitly. Offsets of just a few milliseconds can be audible under the right conditions.
For those using a Dolby DP564 AC-3 decoder, one of monitoring modes uses the analog and digital
outputs. This can inject up to 10 ms of delay into the surround channels, which usually elicits com-
plaints. Either bypass the unit or set the monitoring mode to Digital.
Audio issues disappear in bypass
Since AERO.ASI can apply significant gain to incoming signals, previously inaudible sounds may get
pulled out of the background. We recommend listening carefully to the station audio for hums, buzzes,
clicks, pops, phase issues, frequency response problems, and bass build-up. When amplified, these ar-
tifacts can ruin otherwise excellent programming. Moral of the story: make sure the input audio is im-
maculately clean or it will sound worse in surround!
Audio fixed by re-boot
Re-booting sometimes fixes audio problems by interrupting the AES signals, thereby causing equip-
ment downstream to re-lock to the incoming signals. Selecting a preset with minimal processing (i.e.,
Protection Limit) may shed further light on the problem.
Audio has artifacts
Sometimes described as "squirrels in the surrounds," this is almost always caused by low bit-rate
source content. Some program delivery services or server systems use MPEG 1, Layer 2 audio data
reduction to save bandwidth. At 256 kbps or higher per stereo pair, there are no issues. However, at
or below 128 kbps coding artifacts in the original stereo signal are unmasked by upmixing. This inferior
content has similar results without upmixing if consumers matrix-decode the signal, which is the de-
fault mode for most home A/V receivers. We recommend contacting the program provider or server
manufacturer. Bandwidth is so inexpensive that there is no good reason to run lower than 256 kbps.
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