Audio-Technica AT-MX351 - Manual (Page 4)

Introduction
Please Note!
This manual assumes use of microphone-level inputs and line-level output, the most typical
SmartMixer application. However, all inputs and the output may be individually switched
internally to achieve any combination of mic- and line-level input/output. See page 10 for
details.
What is a SmartMixer?
The AT-MX351 SmartMixer ® is a microprocessor controlled, automatic switching, five-channel
mixer.
The four microphone inputs are XLRF-type balanced, with 48-volt phantom power available on
pins 2 and 3. The Aux input is an RCA jack accepting auxiliary-level input from sources such
as tape decks and VCRs. There is no signal processing of the Aux input. The mixer output is
XLRM-type balanced, non-inverting.
All AT-MX351 and AT-MX341a SmartMixers can be daisy-chained via the included
AT8325/1.0 Link Cable and special connectors on the rear panel. The control bus and the
audio are carried between mixers by the link cable. The result is that all microphones on a
multi-mixer system can be controlled by one microphone connected to any mixer. Since all
of the mixers are independently powered, there is no practical limit to the number of
SmartMixers that can be daisy-chained.
Features
The AT-MX351 provides an independent gain control on the front panel for each input channel.
Substantial gain reserve and adjustment range permit microphones of widely differing sensi-
tivities to be used together successfully. Automatic threshold setting on all mic/line channels
ensures proper gating levels for existing ambient sound conditions.
Priority Pre-select
To custom-tailor conferencing needs, the mode of each microphone channel can be indepen-
dently switched via the front panel “Priority Pre-select” DIP switches. The combination of
switch settings results in three different modes of priority selection/operation.
In any of the three modes of operation, when everyone stops talking, the last microphone “on”
will remain “on.” In a teleconferencing, recording, or broadcast application, this feature will
provide continuous room ambience. This feature is cascaded throughout all linked mixers so
that only one microphone in the entire system will remain on.
When a microphone is “off,” its input is only attenuated. This attenuation is factory set at
8 dB. The amount of “off ” attenuation can be internally adjusted between 6 dB and 40 dB if
desired. (See page 12, “Adjusting ‘Off ’ Attenuation.”)
If automatic switching is not desired, a “manual” DIP-switch setting on the front panel bypasses
the AT-MX351’s automatic switching and attenuation functions, causing the unit to behave
like a conventional mixer. In this mode, the relative level of each microphone is strictly a
function of the position of its respective front-panel gain control.
NOMA (Number of Open Microphones Attenuated)
The NOMA system helps control feedback by allowing for the increase in system gain that
occurs when the number of open microphones increases. A built-in matrix in the AT-MX351
recognizes exactly how many microphones are on and automatically adjusts the gain accord-
ingly. Because use of NOMA is not always appropriate or desired, the AT-MX351 is shipped
with the NOMA function switched off.
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