Studio Technologies 214 - Manual (Page 14)

Issue 1, July 2014 Model 214 User Guide
Page 14 Studio Technologies, Inc.
Microphone Preamplifier Gain
and Phantom Power
Two pushbutton switches, located on the
bottom of the Model 214, are used to set
the gain of the microphone preamplifier
and select the on/off status of the phantom
power source. A 2-digit LED display pro-
vides a status indication of both
functions.
LED Display Time-Out
As previously mentioned, a 2-digit LED
display provides an indication of the gain
of the microphone preamplifier as well
as the on/off status of the phantom power
supply. As a power-saving measure the dis-
play will automatically stop lighting approxi-
mately 100 seconds after the last time that
either of the bottom pushbutton switches
is pressed. A different time-out interval
applies after the Model 214 has had power
applied and neither pushbutton is pressed;
the display will light for approximately 10
seconds and then turn off.
In most cases this display auto-off function
will lead a technician or installer to initially
observe that the 2-digit display is not light-
ing. For example, a Model 214 has been
operating normally but the security panel
has just been removed. To cause the 2-digit
display to again light just requires pressing
either of the bottom pushbutton switches.
This “wakes up” the display and resets the
timer. The initial press of either pushbutton
will not cause the gain to change or impact
the phantom power on/off status. Only
when the 2-digit display is active will the
pushbuttons impact the settings.
Microphone Preamplifier Gain
The two pushbutton switches are used
to select the gain of the microphone pre-
amplifier. The range is 19 to 64 dB in 3-dB
steps. There’s no problem changing the
gain setting while the unit is operating.
Small audio clicks or pops might occur
during gain transitions, but this shouldn’t
be a major issue as long as associated
monitor loudspeakers are temporarily at-
tenuated or muted. As expected, the 2-digit
LED display will directly indicate, in dB, the
selected amount of gain.
Selecting the correct amount of gain for an
application might take a little experimenta-
tion. The goal is to bring the mic’s signal
up to the Dante reference level which is
typically considered to be –20 dBFS. (This
is 20 dB below digital maximum.) Operat-
ing at this signal level will help ensure the
delivery of “clean” audio to the destination
device or devices.
There’s no “perfect” gain setting that this
guide can recommend. The two issues
that impact the setting are output sensitiv-
ity of the connected microphone and the
acoustical output level of the microphone’s
user. With some headset microphones,
such as the Sennheiser HMD26, selecting
an initial setting of 43 or 46 dB would be
appropriate. Users who speak loudly might
need to have the gain reduced to 40 or
even 37 dB. Quiet users might need 49 or
52 dB of gain.
Using the device that’s digitally connected
(via Dante) to the Model 214’s main output
channel is typically the best way to check
the signal level and the setting of the
mic preamplifier. Most devices have
some method of providing an indication
of the digital level, either in the form of
a numerical value, virtual meter, or LED-
based meter display. The Studio Technolo-
gies’ Model 5202 Dante to Phones and
Line Output Interface would also be an
excellent means of monitoring the Model