Studio Technologies 47A - Manual (Page 9)

Model 47A User Guide Issue 1, September 2014
Studio Technologies, Inc. Page 9
Simple Installation
The Model 47A uses standard 3-pin XLR
connectors to allow convenient intercon-
nection in most broadcast and general
audio environments. For flexibility, access
to the 2-wire party-line intercom interfaces
can be made using the connectors pro-
vided on both the front and back panels.
In permanent installations the back-panel
connectors will typically be utilized. In
other settings, such as field television
production, front-panel access allows in-
tercom beltpacks to be rapidly connected,
without requiring access to the inside of a
rack enclosure or necessitating the use of
a secondary input/output (I/O) panel.
The Model 47A is housed in a rugged
aluminum and steel enclosure that is
designed to be “road tough.” It mounts in
one space (1U) of a standard 19-inch rack
enclosure. The mains input source can
range from 100 to 240 volts, 50/60 Hz al-
lowing direct operation virtually anywhere
in the world. A switch-mode power supply,
contained within the Model 47A’s enclo-
sure, provides conversion of the mains
input power into the DC voltage required
by the party-line power supply circuits.
Also contained within the unit is a DC-to-
DC converter that creates the voltages
required by the analog and digital circuitry.
These efficient power supplies help to
ensure cool, reliable operation in a variety
of settings.
Design Philosophy
While the “bits and pieces” that make up
the Model 47A have been described in
conventional terms, the real strength of the
unit rests in how it integrates and performs
in the “real world.” Before beginning the
Model 47A’s design process, conversations
with industry experts quickly made it appar-
ent that installing and configuring existing
2-wire-to-4-wire interface units was invari-
ably a time-consuming, aggravating pro-
cess that required the talent of an expert
to achieve reasonable results. And even
under those constraints the resulting au-
dio performance was often mediocre. Any
new design had to look at the application
in a different way. This led to the over-rid-
ing Model 47A design goal: create a “new
breed of cat,” fundamentally changing how
broadcast 2-wire-to-4-wire interface equip-
ment fit into actual applications.
An important first step was to eliminate
the requirement that a senior technician,
along with a screwdriver, be present dur-
ing every installation. (It was universally
acknowledged that their time can be better
spent elsewhere!) The need to adjust trim
potentiometers, fabricate special cabling
and connector straps, use nulling earpiec-
es, etc., had to be eliminated. For example,
in virtually all instances, input and output
levels fall within just a few dB of their nomi-
nal values and, as such, could be support-
ed with a limited number of configurable
choices. In addition, it was acknowledged
that in this application analog audio cir-
cuitry was capable of providing excellent
audio performance, but that the required
manual nulling process was operation-
ally taxing. By adding digital control to the
analog circuitry, automatic nulling could be
performed—the best of both worlds!
The next step was to identify resources
that would improve the installation process
and make operation more reliable. This
led to the inclusion of multiple LED level
meters, allowing continuous monitoring of
the input and output signals. It also turned