Studio Technologies 41 2007 - Manual (Page 14)

Issue 2, February 2007 Model 41 User Guide
Page 14 Studio Technologies, Inc.
Associated with the audio and DC voltage
monitor functions are four status LEDs,
one pushbutton switch, two 5-segment
LED level meters, a rotary level control,
and a headphone jack. The four monitor
status LEDs are used to indicate which
IFB circuit is currently being audio moni-
tored as well as presenting the status of
the DC output voltages. One of the LEDs
is always lit, indicating which IFB circuit is
currently being monitored by the meters
and headphone output.
Audio Monitoring
The dual 5-segment LED level meters al-
low a direct observation of the audio levels
present on pins 2 and 3 of the selected
IFB circuit’s output connector. In television
broadcast settings, the left meter will typi-
cally display the “interrupt” signal while
the right meter will display “program.” A
quick glance at the meters will give an
accurate overall indication of a circuit’s
performance. During the initial power-up
period, lasting approximately 10 seconds,
the meters may be observed “bouncing”
if the IFB circuit selected for monitoring is
changed. This is normal, caused by DC
blocking capacitors taking a minute or two
to reach their final state.
It’s important to note that the meters on
the Model 41 are calibrated differently
from the typical “VU” scale. The level
steps were selected so as to effectively
display the IFB circuit’s nominal –10 dBu
signal level. The ballistics of the meters
is also different, being a cross between
VU and peak. The bottom four LEDs are
green in color and indicate that signals
are in the normal range. The top LED,
yellow in color, lights when signals are
6 dB or greater above –10 dBu. A correctly
functioning IFB circuit should find signals
lighting the four green LEDs, with the yel-
low LED lighting only on peaks.
The headphone output allows audible
monitoring of the selected IFB circuit.
The 2-channel (stereo) output is compat-
ible with virtually any pair of stereo head-
phones. As the output circuitry meets “pro
audio” specifications, it’s recommended
that high-quality headphones be used.
Pin 2 of the IFB circuit is the signal source
for the left channel of the headphone out-
put. Pin 3 of the IFB circuit is the source
for the right channel. The rotary control
adjusts the output level of both the left
and right channels. Should it be neces-
sary, there’s no reason why the head-
phone output couldn’t also be used as
a line-level monitor output.
Figure 7. Detail of front panel showing dual
5-segment LED level meters
Figure 6. Detail of front panel showing four
status LEDs and associated pushbutton switch