Studio Technologies 230 2014 - Manual (Page 14)

Issue 9, November 2014 Model 230 User Guide
Page 14 Studio Technologies, Inc.
high (+ or hot) is on pin 2 and signal low
(– or cold) is on pin 3. The cable’s shield
can be connected to pin 1, but it will have
no function. To limit the chance of ground-
ing interaction between the Model 230 and
connected equipment, pin 1 on the main
output’s connector is isolated from any
point in the Model 230. The fact that pin 1
“floats” will minimize the chance of hums,
noises, or buzzes being present on the
equipment connected to the main output.
Line-Level Talkback Output
The line-level talkback output is intended
to be connected to control rooms, pro-
duction trailers, or other locations where
talent-originated voice cues are required.
The output is transformer balanced with a
nominal level of +4 dBu. To enhance talk-
back audio quality, a compressor circuit
controls the dynamic range of the signal
coming from the microphone preamplifier.
For protection against accidental connec-
tion to cables that have DC power present,
the line-level talkback output is capacitor
coupled. In series with the talkback output
leads are 300 ohm resistors, making the
effective output impedance approximately
600 ohms. These resistors create a pas-
sive summing network, allowing talkback
outputs on multiple Model 230 units to be
connected together.
The line-level talkback output is connected
by way of a 3-pin male XLR connector
which is located on the Model 230’s back
panel. The mating connector (female)
should be prepared so that signal high
(+ or hot) is expected on pin 2. Signal low
(– or cold) should be expected on pin 3.
The cables’ shields can be connected to
pin 1. But, like the main output, in order
to minimize the chance that ground-in-
teraction problems will arise, pin 1 on the
line-level talkback output connector is
isolated from the Model 230’s chassis and
circuitry. By making pin 1 “float,” an often-
feared “ground loop” problem shouldn’t
arise.
The line-level talkback output is intended
to drive lengthy cable runs that are fre-
quently part of a remote broadcast ap-
plication. While the output circuitry is not
intended to be “on-air” quality, overall
audio performance should be very good.
Devices connected to the line-level talk-
back output can range from amplified
loudspeakers to analog inputs on matrix
intercom systems, and input channels
associated with audio consoles. Connect-
ing the talkback output to devices that
allow easy control of the signal level can
be helpful. For example, connecting to
a spare input channel on an audio con-
sole provides the flexibility to add gain
or attenuate as required. A dedicated
talkback-associated output on the audio
console can then be connected to the final
destination(s).
As previously mentioned, the line-level
talkback output on multiple Model 230
units can be directly connected together.
Using a simple “Y” or “W” cable, this
passive summing (adding together) of
talkback signals allows one audio cable
to serve as a master talkback path. A side
effect from using this passive summing
technique is that signal attenuation will
occur. The audio quality won’t suffer, but
an audio “pad” is created. If two line-level
talkback outputs are connected together,
a signal attenuation of 6 dB can be ex-
pected. Connecting three outputs together
will result in 9.5 dB of attenuation. And
four outputs “multed” together will lead to
12 dB of attenuation. In most cases this at-
tenuation won’t pose a problem. Typically