Studio Technologies M233-01151 - Manual (Page 14)

Issue 5, November 2014 Model 233 User Guide
Page 14 Studio Technologies, Inc.
coming out of the right channel goes into
a “dead” short. There is a simple means
of eliminating this issue; when configuring
the headphone sources simply do not as-
sign any to the right channel headphone
output. Refer to the Configuration section
of this user guide for details.
Main Output
The Model 233’s main output is intended
to be the “on-air” or primary signal that
typically connects to the input of an
audio console. The output is transformer
balanced with a nominal signal level of
–2 dBu. The actual level will depend upon
the gain setting of the microphone pream-
plifier, sensitivity of the microphone, and
how loudly the user speaks into the micro-
phone. The transformer used in the main
output is intended for professional audio
applications. Its source impedance is
very low and can drive lengthy cable runs
without difficulty. It is capable of driving
loads as low as 600 ohms but performs
best with loads of 2 k ohms or greater.
(This should not prove to be an issue as
virtually all contemporary audio equipment
has a relatively high input impedance.)
As the secondary winding of the output
transformer connects directly to the main
output connector, care should be taken
so that a DC voltage is never present on
the interconnecting cable.
The main output is interfaced by means
of a 3-pin male XLR connector located on
the Model 233’s back panel. The intercon-
necting cable’s mating connector (female)
should be wired so that signal high (+ or
hot) is on pin 2 and signal low (– or cold)
is on pin 3. The cable’s shield can be con-
nected to pin 1, but it will have no func-
tion. Also, the cable’s shield must not be
terminated on the metal “shell” connec-
tion of the mating connector. To limit the
chance of grounding interaction between
the Model 233 and connected equipment,
pin 1 on the main output’s connector is
isolated from any point in the Model 233.
The fact that pin 1 “floats” will minimize
the chance of hums, noises, or buzzes be-
ing present on the equipment connected
to the main output.
Line-Level Talkback Outputs
The two line-level talkback outputs are
intended to be connected to control
rooms, production trailers, or other loca-
tions where talent-originated voice cues
are required. The outputs are transformer
balanced with a nominal level of +4 dBu.
To enhance talkback audio quality, a com-
pressor circuit controls the dynamic range
of the signal coming from the microphone
preamplifier.
For protection against accidental connec-
tion to cables that have DC power present,
the line-level talkback outputs are capaci-
tor coupled. In series with the talkback
output leads are 300 ohm resistors, mak-
ing the effective output impedance ap-
proximately 600 ohms. These resistors
create a passive summing network, allow-
ing talkback outputs on multiple Model
233 units to be connected (“bridged”)
together.
The line-level talkback outputs are con-
nected by way of two 3-pin male XLR con-
nectors which are located on the Model
233’s back panel. The mating connectors
(female) should be prepared so that signal
high (+ or hot) is provided on pin 2.
Signal low (– or cold) should be provided
on pin 3. The cables’ shields can be con-
nected to pin 1. But, like the main out-
put, in order to minimize the chance that
ground-interaction problems will arise,
pin 1 on the line-level talkback output