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Issue 1, September 2007 Model 233 User Guide
Page 34 Studio Technologies, Inc.
to the connected headphones. The user
can now, in response to changing condi-
tions, adjust the front-panel level controls
as desired. Returning the controls to their
detent positions will always provide the
“reference” level to the headphone output.
A second example has the intercom input
and line input 1 both providing cue sourc-
es. Pin 2 of the intercom circuit supplies
program-with-interrupt audio that is routed
to the headphone output’s left chan-
nel. Pin 3 of the intercom circuit supplies
program-only audio that is routed to the
right channel. Line input 1 is connected to
an audio source associated with a sports-
event “spotter” position. This source is
routed to the headphone output’s right
channel. The input trim pot associated
with line input 1 can now serve a critical
role—adjusting the relative level of the
“spotter” audio as compared to the level
of intercom pin 3. The trim pot allows the
desired “mix” to be created, providing the
user with an effective cue signal.
Intercom Interface Sidetone
Adjustment
Associated with the talkback-to-intercom
functions are sidetone trim potentiometers
that are used to adjust the talkback levels
that are returned by way of the intercom
line cue audio source circuitry. These two
trim pots are part of the analog hybrid cir-
cuit that separates (nulls) talkback audio
from receive (listen) audio. If audio from
either or both of the intercom channels is
to be used as a headphone source, and
talkback to these intercom channels has
been configured, the sidetone trim pots
may need to be adjusted.
One trim pot is associated with the side-
tone level for each channel of the inter-
com interface. Both are accessible on
the bottom of the Model 233’s enclosure,
adjacent to the trim pots associated with
the line-level inputs. Adjusting them is very
simple, requiring only a pair of ears and a
screwdriver.
With the Model 233 configured as previ-
ously described, activate one of the talk-
back-to-intercom functions. Audio from
the connected microphone may be heard
in the configured headphone output
channel(s). Adjust the trim pot associated
with the active intercom channel so that
the desired sidetone level, relative to the
intercom receive level, is achieved. The
adjustment range is approximately 18 dB,
with the sidetone level increasing as the
trim pot is rotated in its clockwise direc-
tion. Now change to the other intercom
channel and adjust its sidetone trim pot
as desired.
Using the Model 233’s sidetone func-
tion, talkback audio will be routed to the
headphone outputs by means of active
circuitry. If this is enabled be certain to
place the two intercom sidetone trim pots
to their fully counterclockwise positions.
This will minimize the increase in sidetone
level that will occur when both the main
sidetone and the sidetone associated with
talkback-to-intercom functions are active.
Technical Notes
Grounding and Shielding
As previously discussed in this user guide,
the pin 1 connections on the 3-pin male
XLR-type connectors associated with the
main and line-level talkback outputs are
“floating,” i.e., not connected to anything
within the Model 233’s enclosure. Some
audio experts might take offense to this,
grousing that this should have been left