Issue 2, December 2013
Model 42A User Guide
Page 12
Studio Technologies, Inc.
twisted-pair cable rather than worrying
about whether or not it is shielded. The foil
shields typically provided in many of types
of audio cables generally offer very limited
effectiveness. The best rule to follow is to
try to minimize exposure to large noise
sources. (Okay, so that’s hardly ever prac-
tical but at least it’s a nice dream!)
In the event that very long cable runs are
required, the resistance of the cable can
impact the DC power supplied by the
Model 42A. There’s no way to get around
the fact that some DC voltage will be
dropped in the interconnecting cable(s). A
simple “ohms law” calculation will tell you
the impact that a cable run will have. You’ll
need to know the exact cable length, the
current draw of the connected device(s),
the minimum voltage required by the con-
nected device(s), and the resistance of the
cable’s conductors. This is generally stat-
ed as ohms per 1000 feet. Make sure that
you account for the resistance in both the
pin 1 and pin 2 legs! In general, if there is
the potential for a cable-length problem,
moving to a more substantial cable gauge,
such as 20 or 18 AWG, can be effective.
AC Mains Power
The Model 42A operates directly from AC
mains power over the range of 100 to
240 V, 50/60 Hz. Being a “universal input”
device, there are no switches to set or
jumpers to install to match a location’s
nominal AC mains voltage. The Model 42A
uses a 3-pin IEC 320 C14 inlet connector
to mate with a detachable AC mains cord.
All units are supplied with an AC mains
cord that has a North-American (NEMA
5-15P) standard plug on one end and
an IEC 320 C13 connector on the other
end. Units bound for other destinations
require that the appropriate cord set be
obtained. The wire colors in the AC mains
cord should conform to the internationally
recognized color code and be terminated
accordingly:
Connection
Wire Color
Neutral (N)
Light Blue
Line (L)
Brown
Earth/Ground (E) Green/Yellow
Safety Warning:
The Model 42A does
not contain an AC mains disconnect
switch. As such, the AC mains cord
plug serves as the disconnection
device. Safety considerations require
that the plug and associated inlet be
easily accessible to allow rapid dis-
connection of AC mains power should
it prove necessary.
As soon as AC mains power is applied
the Model 42A will begin its power-up
sequence. As a “boot-up” indication
each of the front-panel LEDs will light in a
processor-controlled sequence. After that
has completed one of the status LEDs will
remain lit. The unit is now fully operational.
Post-Installation
Audio Input Source Level
Adjustment
It’s important to confirm and, if required,
adjust the level of the audio sources
that are connected to the Model 42A’s
audio inputs. The monitor section’s dual
5-segment LED level meters will help
make this task simple. Begin by using
the pushbutton switch, located on the
front panel, to select the IFB output that is
going to be calibrated. Adjust the source
levels so that the four green LEDs light
