Studio Technologies 230 2014 - Manual (Page 19)

Model 230 User Guide Issue 9, November 2014
Studio Technologies, Inc. Page 19
Unfortunately, there’s no “perfect” gain
setting that this guide can recommend.
The two issues that impact the setting are
output sensitivity of the connected micro-
phone and the acoustical output level of
the microphone’s user. With some headset
microphones, such as the Sennheiser HMD
26, selecting an initial setting of 40 dB is
appropriate. Users who speak loudly might
need to have the gain reduced to 30 dB.
Quiet users might need 50 dB of gain.
An LED indicator is provided as an aid in
correctly setting the gain of the microphone
preamplifier. Red in color, this LED is
located adjacent to switch assembly 1.
It is visible by observing the bottom of the
Model 230’s enclosure when the security
plate has been removed. Technically, this
red LED lights whenever the compressor cir-
cuitry is controlling the dynamic range of the
signal coming from the microphone pream-
plifier. The threshold is set to be 2 dB above
the Model 230’s nominal internal operating
level. So a good “rule of thumb” is to adjust
the gain of the microphone preamplifier
such that the compressor active LED lights
(“flashes”) when the connected microphone
is sending signal peaks. During normal
operation the LED should not remain fully
lit when audio is present on the mic input.
It’s important to remember that the com-
pressor active LED is used to assist in set-
ting the gain to the optimal value. It doesn’t
necessarily indicate that the main output’s
signal is being compressed. Unless specifi-
cally configured to perform otherwise, the
output of the compressor is only used for
the talkback output.
It’s expected that the 20 and 60 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 phantom-
powered condenser-type, 20 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 60 dB
of gain. But in general, the 30, 40, and 50
dB gain settings will serve most applica-
tions.
Note that if no gain switch is set to its ac-
tive (on) position the preamplifier will oper-
ate at unity (0 dB) gain. This is provided
for compatibility when line-level signals
need to be connected to the microphone
input. But with a microphone 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 outputs will be much
too high.
Phantom Power On/Off
The Model 230 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 required for a specific
microphone.
Figure 5. Phantom power switch settings