Studio Technologies 230 2008 - Manual (Page 14)

Issue 7, October 2008 Model 230 User Guide
Page 14 Studio Technologies, Inc.
so that DC voltage is never present on the
interconnecting cable.
The main output is interfaced by means of
a 3-pin male XLR-type connector located
on the Model 230’s back panel. The in-
terconnecting cable’s mating connector
(female) should be wired so that signal
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, production
trailers, or other locations where talent-
originated voice cues are required. The out-
put is transformer balanced with a nominal
level of +4 dBu. To enhance talkback 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-type connec-
tor 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-
interaction 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
frequently part of a remote broadcast
application. While the output circuitry is
not intended to be “on-air” quality, over-
all audio performance should be very
good. Devices connected to the line-level
talkback output can range from ampli-
fied loudspeakers to analog inputs on
intercom systems, and input channels
associated with audio consoles. Connect-
ing the output to devices that allow easy
control of the signal level can be helpful.
For example, connecting to a spare input
module on an audio console 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,