Studio Technologies 200 - Manual (Page 19)

Issue 3, August 2004 Model 200 User Guide
Page 20 Studio Technologies, Inc.
source must provide 50 milliamperes at
24 volts DC.
It’s worth discussing what will happen if
either power source falls below its specified
minimum. Typically, if the Model 200 is be-
ing powered by an external power source,
apparently normal operation will continue
until the input falls to the 18-20 volt range.
The Model 200’s internal power supply will
have reduced stability until its low-voltage
shutdown circuit halts its operation. Note
that as the input voltage moves down from
24 volts the input current will rise propor-
tionately to make up for the loss of power.
If an IFB circuit is powering the Model 200,
maintaining the required voltage and cur-
rent is more critical. Should the voltage or
current fall below the specified minimum,
the Model 200’s power supply circuit will
again become unstable. This will become
an issue as noise will be induced into the
IFB circuit’s audio signals. The reason
is simple: an IFB circuit “multiplexes”
3-conductors so that they carry both power
and audio signals. If sufficient amounts of
voltage and current are presented to the
IFB input, the Model 200’s power supply
draws a nice and steady amount of energy.
This will not disturb the analog signals
on pin 1 (common for DC and audio) and
pin 2 (DC and channel 1 audio). But if the
Model 200’s power supply is not presented
with sufficient energy it will try to draw what
it needs from the IFB circuit, becoming
unstable in the process. The IFB circuit’s
audio signals will be corrupted by the
power supply’s attempt to draw enough
power. Instead of nice clean audio there
will be squeaks, squeals, and some awfully
funky noises added. Again, in a low-voltage
or low-current situation, no damage will be
done to the Model 200’s circuitry but cor-
rect operation will not be possible.
In most cases maintaining the IFB circuit’s
required voltage and current shouldn’t
be a problem. But issues may arise due
to malfunctioning IFB sources or poor
interconnect cabling. Typically, excessive
cable length won’t be the cause of a prob-
lem. Generally, problems will be caused
by broken or damaged connector pins,
dirty patch points, or damaged (partially
open) cable conductors. Measuring the IFB
circuit’s voltage and current draw directly
at the Model 200’s IFB input connector will
quickly identify if there’s a power issue.
And now for another shameless “plug” for
other Studio Technologies products: Frank-
ly, most devices that supply IFB circuits
for broadcast applications use outdated
technology that provides mediocre perfor-
mance. That’s why Studio Technologies’
developed high-performance IFB interface
units. These products do an excellent job
of providing power and audio to connected
devices such as the Model 200. However,
unlike other products, the power supplied
by these units’ IFB circuits maintain their
output voltage all the way to their full rated
current. The result is being able to power
more devices over longer cable runs. In
addition, the audio quality of these units
is superior. For further information please
refer to the Studio Technologies website.
LED Colors
As previously described, two LED indica-
tors are associated with the main output
and are located directly above the main
output pushbutton switch. The red LED,
located on the left, is lit whenever the main
output is muted. The green LED, located
on the right, is lit whenever the main output
is active. The thought process behind the
color choices was that red would relate to
the main output being muted (“stop”) while