Studio Technologies 200 - Manual (Page 17)

Issue 3, August 2004 Model 200 User Guide
Page 18 Studio Technologies, Inc.
a “hit-or-miss” proposition. During field
testing of prototype announcer’s consoles,
Studio Technologies’ personnel found
that a wide range of nominal audio levels
were present on “real-world” IFB circuits.
Many were fine, being reasonably close
to –10 dBu. But some were much too low,
while others much too “hot.” We observed
one unfortunate baseball “color” commen-
tator being sent interrupt audio signals
so “hot” relative to program audio as to
almost make his ears bleed! This situation
should not have been allowed to happen.
In defense of field technical personnel,
measuring the audio level of an IFB circuit
hasn’t traditionally been an easy proposi-
tion. But that situation has now changed.
After experiencing this condition in the
“field,” Studio Technologies’ engineers
were motivated to design the Model 72
Level Meter/Interface. This compact
device plugs directly into IFB and intercom
circuits and provides two useful functions:
level meters and “dry” audio outputs.
Two 5-segment LED meters allow direct
observation of the audio signal levels
present on IFB or intercom circuits. The
display range is optimized for the signal
levels found on these circuits, rather than
traditional “VU” scaling. The Model 72 also
provides two transformer-coupled “dry”
audio outputs, one for each IFB or inter-
com channel. These outputs are useful for
a variety of production and testing applica-
tions. For example, the outputs can serve
as the interface between a traditional “wet”
IFB system and a wireless in-ear monitor
system. The outputs can also be connect-
ed to a monitor panel, allowing visual and
aural monitoring of the IFB audio signals.
In conclusion, we’re sorry for this shame-
less promotion of the Model 72 Level
Meter/Interface! But necessity was
definitely the “mother” when it came to
the unit’s invention. Working “in the field”
without such a device, we felt “blind” when
connecting to IFB circuits. That no longer
has to be the case and we think that you’ll
finding owning one a very worthwhile
investment. For further information please
refer to the Studio Technologies website.
Phantom Power
The Model 200 provides a 48 volt nom-
inal source of “phantom power” to sup-
port condenser-type microphones. It’s
designed to meet the P48 requirements as
specified in the IEC 61938 standard. The
circuitry is very simple: two 6.81 k ohm
resistors provide a path from a 48 volt
source to pins 2 and 3 of the microphone
input connector. The resistors and the
power source work together to provide 48
±4 volts, up to a maximum current of 10
milliamperes.
External Power Sources
As has been previously discussed, an
external source of 24 volt DC can be used
to power the Model 200. While develop-
ing the 200-series of announcer console
products, an interesting phenomenon was
discovered regarding acceptable sources.
To meet worldwide requirements, using
a compact switch-mode “universal input”
power supply seemed to be an excellent
solution. Supplying one of these with each
Model 200 would have allowed operation
anywhere in the world. Whether connect-
ing to 100 volts, 60 Hz in Japan or 240
volts, 50 Hz in Australia all would be well.
Unfortunately, things did not work out as
planned! It turned out that all of the com-
pact switch-mode power supplies that
were tested induced a great deal of noise
into their DC output. This noise, especially