page 2 – 10
AirAura X1 / Dec 2016
F R O N T P A N E L G U I
Where and When to Use Pre-Emphasis and De-Emphasis
Pre-emphasis was designed to help reduce the background noise of FM broadcasts. By
raising high frequencies in the transmission system and applying a complimentary filter
in the receiver, we gain additional signal to noise ratio for the listener.
Most processors have many options for applying pre-emphasis and de-emphasis. It
can get confusing. So we will try to cover all the basics here.
If You Are Using the Analog Composite Outputs in the X1
Pre-emphasis should be applied. If you are using the analog or AES output to feed
headphones, you should de-emphasize these outputs or they will sound too “bright”.
If You Are Using baseband192 (AES Composite) to Feed Your Exciter
Pre-emphasis should be applied. If you are using the analog output to feed headphones,
you should de-emphasize these outputs or they will sound too “bright”.
If You Are Using an AES/EBU Connection to the Exciter (where the exciter
performs the stereo generator function)
Pre-emphasis should be applied AS WELL AS de-emphasis to the AES signal. This
act will apply the proper peak control when pre-emphasis is re-applied later in the exciter.
If you set the X1’s pre-emphasis to FLAT and apply pre-emphasis at the exciter, you will
be prone to gross overshoot as many exciters do not have overshoot filters to control
pre-emphasis. The best (and not always available) option if you must use an AES/EBU
connection that is not composite is to perform pre-emphasis at the processor before a
linear STL path and NOT perform any further emphasis in the exciter.
Using the AES FM Output to Feed a Codec
Pre-emphasized audio (with or without de-emphasis) should never be applied to an
audio codec. If you need processing for streaming from your X1, the HD AES/EBU output
or the analog outputs (set for HD) should be fed to your stream. Feeding audio managed
for FM to an internet stream will unveil artifacts. If you must feed your stream with audio
processed for FM, you should not expect great results.
NOTE: For more information on setting de-emphasis for the outputs on the X1,
please see page 2-20.