Studio Technologies 212 2013 - Manual (Page 17)

Model 212 User Guide Issue 5, May 2013
Studio Technologies, Inc. Page 17
that the compressor active LED will light
(“flash”) only when the connected micro-
phone is sending signal peaks. During
normal operation the LED should never
remain fully lit when audio of typical signal
level is present on the mic input.
If the threshold is set for –4 dBFS the LED
should light only on extreme signal peaks,
or possibly never. This is because with
a –4 dBFS threshold the compressor is
intended only to prevent signals from ever
causing the maximum digital level of 0
dBFS to be reached. It’s not supposed to
reduce the dynamic range of normal pro-
gram material. As an aid in setting the mi-
crophone preamplifier’s gain, it might be
useful to temporarily set the compressor’s
threshold to –14 dBFS. Once the gain has
been set so that the LED lights only on
peaks the threshold can be returned to
the –4 dBFS setting.
It’s expected that the 10 and 50 dB gain
settings will not often be used. But there
are always exceptions and that’s why they
were included. It’s possible that with a
very “hot” microphone, such as a phan-
tom-powered condenser-type, 10 dB of
gain could be correct. It’s also possible
that a microphone with a very low-level
output, such as a ribbon-type, would need
50 dB of gain. But in general, the 20, 30,
and 40 dB gain settings will serve most
applications.
Note that if no gain switch is set to its
active (on) position the preamplifier will
operate at unity (0 dB) gain. With a mi-
crophone connected as the input source
one should never use the 0 dB setting.
The issue is that with no gain added to the
microphone input signal, the relative noise
floor on the main and talkback output
channels will be much too high.
Figure 5. Phantom power switch settings
Phantom Power
The Model 212 can provide 48 volt nomi-
nal phantom power to the connected
microphone. Switch SW1-8 controls
whether or not phantom power is active.
By phantom power’s very nature it could
be left applied to the microphone input at
all times. But generally people prefer to
turn it off unless it is required for a specific
microphone.
Compressor Threshold
An analog audio compressor circuit is
provided to control the dynamic range of
the signal coming from the output of the
microphone preamplifier. Switch SW1-7
is used to select the threshold (level) at
which the compressor circuit will actively
begin controlling the signal’s dynamic
range. Two choices are available, –14 or
–4 dBFS, which refer to the signal level
in dB below the maximum digital output
level. (The maximum level of a digital au-
dio signal is typically referred to as 0 dBFS
with FS indicating full scale or all bits
being “1”s.) Setting the threshold for –14
dBFS would provide 6 dB of level above
Figure 6. Compressor theshold switch settings