Studio Technologies 220 2013 - Manual (Page 31)

Model 220 User Guide Issue 5, February 2013
Studio Technologies, Inc. Page 31
IFB circuits “dry” (no DC) and differential
(balanced). This would gain the benefits of
differential transmission, including mini-
mizing the crosstalk. The balanced line-
level signals can be directly connected to
the Model 220’s line inputs. However, if
it’s desired to connect cue sources to the
Model 220 using an IFB circuit, the line-
level audio signals will need to be “wet-
ted up” into standard IFB circuits. This is
easily accomplished using one of several
high-performance IFB interface units from
Studio Technologies. For further informa-
tion please refer to the Studio Technolo-
gies website.
IFB Audio Levels
The Model 220 is designed to operate
best with IFB audio levels that are nomi-
nally –10 dBu. This is the nominal level of
most IFB systems. But actually having the
correct level present on an IFB circuit is of-
ten 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 the
desired –10 dBu. But some were much too
low, while others were much too “hot.” We
observed one unfortunate baseball “color”
commentator 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 de-
vice 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 obser-
vation 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 trans-
former-coupled “dry” audio outputs, one
for each IFB or intercom channel. These
outputs are useful for a variety of produc-
tion and testing applications. 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 connected to a moni-
tor panel, allowing visual and aural moni-
toring 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 defi-
nitely the “mother” when it came to the
unit’s invention. Working “in the field” with-
out 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
find owning one a very worthwhile invest-
ment. For further information please refer
to the Studio Technologies website.
Phantom Power
The Model 220 provides a 48 volt nomi-
nal source of phantom power to support
condenser microphones. It’s designed to
meet the P48 requirements as specified
in the IEC 61938 standard. The circuitry
is very simple: 6.85 k ohm resistors pro-
vide a path from a 45 volt source to pins 2
and 3 of the microphone input connector.