Studio Technologies 220 2008 - Manual (Page 32)

Issue 4, October 2008 Model 220 User Guide
Page 32 Studio Technologies, Inc.
stability, operating in this manner until its
low-voltage shutdown circuit halts opera-
tion. Note that as the input voltage moves
down from 24 volts the input current will
rise proportionately to make up for the
loss of power.
If an IFB circuit is powering the Model 220,
maintaining the required voltage and cur-
rent is more critical. Should the voltage or
current fall below the specified minimum,
the Model 220’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 pow-
er and audio signals. If sufficient amounts
of voltage and current are supplied to the
Model 220’s IFB input, the Model 220’s
power supply will draw a steady amount
of energy. This will not disturb the analog
signals on pin 1 (common for DC and au-
dio) and pin 2 (DC and channel 1 audio).
But if the Model 220’s power supply is
not supplied with sufficient energy (volts x
amps) 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 220’s circuitry but correct
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 circuit sources or
poor interconnect cabling. Typically, ex-
cessive cable length won’t be the cause
of a problem. Generally, problems will be
caused by broken or damaged connector
pins, dirty patch points, or damaged
(partially open) cable conductors. Measur-
ing the IFB circuit’s voltage and current
draw directly at the Model 220’s IFB input
connector will quickly identify if there’s a
power issue.
And now for another shameless “plug”
for other Studio Technologies products:
Frankly, most devices that supply IFB
circuits for broadcast applications use
outdated technology that provides medio-
cre performance. That’s why Studio Tech-
nologies’ developed high-performance
IFB interface units. These products do an
excellent job of providing power and audio
to connected devices such as the Model
220. 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 pro-
cess behind the color choices was that
red would relate to the main output being
muted (“stop”) while green would relate
to the main output being active (“go”). It’s
possible that these color choices may not
meet the needs of all users and applica-
tions. For example, it’s reported that one
European broadcaster typically uses these