Studio Technologies 761 - Manual (Page 35)

Model 761/771 User Guide Issue 1, March 2008
Studio Technologies, Inc. Page 35
for Surround
Technical Notes
Dialnorm
A source of Dolby E metadata can be con-
nected to the Model 761 Central Controller.
Within this fl ow of metadata frames will be
a “dialnorm” level value that’s associated
with the 5.1 surround signal that serves
as the Model 761’s HD primary input. The
dialnorm level value can be displayed by
the Model 771 Control Console and used
to control the monitor output level.
Technically, the metadata is in the form
of a 115.2 kbit/s RS-485/RS-422 signal
that contains a number of data elements,
including one or more that represent the
average dialog level (dialog normalization
or dialnorm) in the audio program signals
being carried over the digital audio por-
tion of the related Dolby E interface. These
dialnorm levels are associated with spe-
cifi c programs within the 8-channel audio
“stream.” Firmware within the Model 761 is
able to parse (separate) the data elements,
specifi cally separating the fi rst dialnorm
level value in the metadata frame from the
one or more that may be present later. To
clarify, any dialnorm level elements that
occur later in the same metadata frame
are ignored. This method was selected as
it was assumed that the fi rst dialnorm level
element will always be associated with a
5.1 program. There’s a technical basis for
why this should be true. In Dolby E a 5.1
program is always assigned to the fi rst six
channels (channels 1-6). While there may
be separate dialnorm values associated
with audio channels 7 and 8, they are not
relevant for correct StudioComm system
operation.
Downmix
The downmix functions are implemented
in the Model 761 Central Controller’s
hardware using analog circuitry. The 5.1
to stereo downmix function performs this
action: center (C) dropped in level by 6 dB
and routed to left (L) and right (R) monitor
outputs; left surround (LS) dropped in level
by 3 dB and routed to L monitor output;
right surround (RS) dropped in level by
3 dB and routed to R monitor output; low-
frequency-enhancement (LFE) input mut-
ed. The stereo to mono downmix function
performs this action: L dropped in level by
3 dB and routed to the C monitor output;
R dropped in level by 3 dB and routed to
the C monitor output; C, LS, RS, and LFE
inputs mute.
“Hot” Disconnection of the
Model 771 Control Console
There’s no problem relocating the Model
771 Control Console while your Studio-
Comm system is operating. You can dis-
connect the 9-pin interconnecting cable,
move the unit, and then re-connect without
issue. Upon disconnection the Model 761
Central Controller will mute the moni-
tor output channels as well as saving the
current operating parameters. No clicks,
pops, or other noises will occur when the
Model 771 is again connected. The Model
771 will go through its standard power-up
sequence and then normal operation will
resume.
Monitor Output Transient
Protection
The Model 761 Central Controller contains
a power-up/power-down transient protec-
tion feature. This limits the chance of