BM-‐AV1-‐E16SHD
2012
Version 2.1
Page 8
Using the DOLBY MIX switch
Dolby E encoding allows several separate ‘programs’ or groups of audio to be carried in
the same data stream. The
DOLBY MIX
switch allows individual mix-downs and channels
within a Dolby E program to be monitored. Available mix-downs are selected with the
DOLBY MIX
switch. The selected signal is sent to the left and right speakers and the first
two bargraphs (left most looking at the front of the unit).
The following example may help to explain the facilities provided. Consider the situation
where a studio wants to convey a surround sound music signal together with two technical
commentaries for transmitter operators. For the surround sound component, a 5.1
configuration might be ideal since it has 5 audio channels and one LF effects channel.
However, the two independent engineering feeds (two different languages and not for
transmission) can be encoded into two unused channels to give a configuration of
5.1+1+1.
The Dolby mix-‐down
The operator at the transmitter might want to listen to the music but not necessarily in full
surround sound. Fortunately, the Dolby decoder has an internal buss, which carries a mix-
down. This is a stereo signal that contains a mixture of, in this case, all 6 music signals with
any phasing or special effect applied. The Dolby decoder ‘knows’ that the audio is encoded
as 5.1+1+1. In order to listen to the engineering feeds it must be possible to direct the
decoder to select the 5.1, +1 or other +1 signals and output the appropriate mix-down to
the buss. The three separately encoded audio ‘programs’ can be selected using the
DOLBY MIX
switch. Clearly the mix-down of the +1 signals will be a simple mono signal.
When the BM-AV1-E16SHD is in any of the P1 to P8 program select modes (or Dolby
Down-Mix modes), the stereo audio available on the internal buss is sent to the left and
right speakers and to bargraphs 1&2.
Independent mode
All of the Dolby E audio signals can be decoded and made available on their own (i.e., not
mixed) by setting the
DOLBY MIX
switch to the independent position (
IND
).
In the 5.1 +1 +1 example, music might be presented on bargraphs 1 to 6 and the two
engineering feeds on bars 7 and 8. It is then easy to select which of these to listen to by
pressing the button under the appropriate bargraph. A mix down of some or all of the
channels can be obtained by selecting several audio signals to be sent to each speaker.
Note:
Independent mix-down does not apply all of the phasing effects of the Dolby mix
down modes.
Directing sources to speakers
Where more than two audio signals are present it may be useful to direct and combine
sources to selected speakers. The left speaker is indicated by a red LED and the right by a
green LED on the top of the bargraphs.
To direct a particular source to the left or right speakers proceed as follows:
Repeatedly press the button under the bargraph corresponding to the input audio signal
required until the top LEDs of the bargraph shows red for the left speaker, green for the
right or both to direct the audio to both speakers. Each speaker can receive a mix of audio
from inputs 1 to 16. Select either lower or upper 8 sources using the select button.
Note that the mix button assignments are retained over power-down.
