Model 50/51 User Guide
Issue 6, September 2004
Studio Technologies, Inc.
Page 33
terminated with 600 ohm loads. In this way
it was easy to say that 0dBm is 1 milliwatt
dissipated in the known load (i.e., 0dBm
across 600 ohms will measure 0.775V).
In contemporary situations an output is
rarely terminated with 600 ohms; gener-
ally 10k ohms or higher. The dBu desig-
nation is better because it refers to dB
referenced to 0.775V, with no reference to
load impedance. This takes into account
today’s audio scene where signals have a
low source impedance, and a high input
impedance. The dBu designation is be-
coming the
standard for the professional
audio industry.
StudioComm equipment is designed to
interface with audio signals that have nom-
inal signal levels of –10dBV and +4dBu.
You might wonder why dBV came into
the picture. Most people don’t realize that
equipment that utilizes “–10” levels usu-
ally mean –10dBV—substantially different
from –10dBu (–10dBV = –7.78dBu). The
dBV designation is simply a different way
of measuring signal level and is often used
when dealing with portable or consumer
audio equipment. The dBV designation
refers to dB referenced to 1.0V, rather than
dBu which refers to 0.775V.
“Hot” Disconnection of the Model 51
Control Console
Should you need to relocate the Model 51
while your StudioComm system is oper-
ating, there is no reason why you can’t
disconnect the 5-conductor cable, move
the unit, and then connect it again. If the
Model 51 is disconnected while it is op-
erating, the current operating parameters
are saved in nonvolatile memory and the
Model 50 Central Controller will continue
to operate as it did when the link was
broken. No clicks, pops, or other noises
will occur when the Model 51 is again
connected. The Model 51 will go through
its standard power-up sequence, send a
message to reset power-up defaults, then
send the operating parameters as stored
in its memory. You may notice a brief inter-
val of silence while the Model 50 responds
to the reset defaults message.
Control Room Mono Function
Many arguments where had while design-
ing the control room monaural function.
Was the function supposed to be a true
mono function, sending the sum of left
and right to a separate mono control
room output? Was mono to be the sum
of left and right sent to both left and right
channels? What about level build up with
phase coherent signals that are in both
the left and right channels? After much
head scratching it was realized that the
mono function that most people are ac-
customed to is really a means of observ-
ing the character of a stereo mix, and not
a “true” mono function. To observe the
stereo image of a mix you need to sum
the left and right signals, drop the level of
the sum, and send the result out the left
and right outputs. In our implementation,
we drop the level by 6dB. This is what
many recording consoles implement, and
is what the StudioComm does too! We
understand that specialized applications
such as mastering and film mixing may re-
quire a more exotic mono function. Sorry,
our hardware simply can’t support it!
Talent Amplifier Mono Function
The Model 35 and Model 38 Talent
Amplifiers each contain a monaural
switch. The mono function sums the left
and right input signals, drops the level of
the sum by 6dB, and sends the sum to
both the left and right outputs.