Studio Technologies M233-01151 - Manual (Page 35)

Model 233 User Guide Issue 5, November 2014
Studio Technologies, Inc. Page 35
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 connectors associated with the main
and line-level talkback outputs are “float-
ing,” i.e., not connected to anything within
the Model 233’s enclosure. Some audio
experts might take offense to this, grous-
ing that this should have been left to the
user or installer to be connected or dis-
connected as desired. However, repeated
field testing found that floating pin 1 on
these outputs was the key to maintaining
quiet audio. From Fenway Park in Boston,
to the Orange Bowl in Miami, and then
northwest to Husker Stadium on the
Nebraska Plains, lifting pin 1 always did
the trick.
A simple solution is available if an
application does require that a ground
be available on the main and line-level
talkback outputs’ interconnecting cables.
All Model 233 XLR connectors have a
ground connection that is made to the
interfacing connector’s metal “shell.” And
most XLR connectors have a pin or con-
nection point available to access its metal
shell. By connecting the cable shield to
the mating connector’s shell terminal, the
common connection typically found on
audio interconnections is created.