Omnya AM 41443 User manual

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AM 41443
AUTOMIXER
PREAMPLIFIER
User’s Manual
Rel. 1.01
24/09/2007

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SUMMARY
1 FOREWORD
1.1 Thanks
1.2 The automatic mixer preamplifier
1.3 The package contains
2. DESCRIPTION
2.1 Block diagram and description
2.2 Front panel of AM41443
2.3 Rear panel of AM41443
3. THE CIRCUIT
3.1 Front panel switch
3.2 Microphone channel
3.3 Tone controls
3.4 Master balanced output
3.5 Auxiliary balanced output
3.6 USB control port
3.7 RS232 control port
3.8 Daisy-Chain connectors and RS485 port
3.9 Internal selections
4 OPERATING MODES
4.1 Manual
4.2 Mixer Stand-alone
4.3 Mixer Daisy Chained
4.4 Programming and controlling
4.5 Master and Slave
5 PROGRAMMING
5.1 Reset
5.2 Indications from the VU-meter
5.3 LED for status channel indication
5.4 Default settings
5.5 Behaviour with the manual selections
6 INSTALLATION
6.1 Mechanical installation
6.2 Plugging into the mains
6.3 Ground loop
6.4 Microphone lines
7 USING THE AUTOMIXER
7.1 Church setup
7.2 Conference room setup
7.3 Videoconferencing setup
7.4 Broadcast uses
8. TECHNICAL CHARACTERISTICS AND PERFORMANCES
8.1 List of the controls available for remote control:
8.2 Technical Data
APPENDIX OPERATING FUNCTIONS
A.1 AMB-THR
A.2 Last-On
A.3 One-On
A.4 LOM
A.5 NOM
A.6 ORG
A.7 NOISE GATE
A8 LIMITER

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1. FOREWORD
1.1 THANKS
Congratulations! You have chosen an Omnya brand product. The automatic mixer and
preamplifier AM41443 is a high technology device engineered to solve numberless
problems with an incredibly easy use. We hope you will be completely satisfied with this
product’s features.
1.2 THE AUTOMATIC MIXER
When installing a P.A. system where loudspeakers and microphones are located in the same
room, two contrasting requirements need to be met: an adequate sound level has to be
achieved to ensure intelligibility, but feedback must not be triggered.
Problems come up especially when several microphones are used, as the installer has to adjust
each of them to the required sensitivity when in use. However, when all the microphones are on,
overall sensitivity increases significantly as well, by 3 dB each time the number of microphones
doubles. We thus have +3dB when going from one to two microphones, +6dB from two to four,
+9dB from four to eight. The sensitivity increase easily moves the system into the feedback-
triggering zone and the overall gain has to be reduced to move back into the safe zone. This
way however, each individual microphone no longer has its optimum sensitivity. In general, the
final setting is a possibly poor compromise, with the significant drawback that, especially in a
reverberating environment, any microphone that is open and not engaged picks up and feeds
reverberated sound into the system: even when feedback is not triggered, the returning sound
tail blurs the direct sound.
AM41443 belongs to a new generation of automatic mixers under the OMNYA brand.
It is a small mixer working both manually and automatically, with a total modularity that avoids
real limits to the number of channels. This also means that more AM41443s can be installed
locally or in different places and controlled through a PC connection or a remote control panel.
It can work as manual or automatic stand-alone or through a USB port controlled mode.
The AM41443 main characteristic is that the audio signal is analog. The high quality
microphone front end maintains a very low distortion and a maximum signal/noise ratio. With
its 20dB headroom it guarantees a perfect result in any condition. This automatic mixer is
produced in a ½ rack unit metallic box.
A powerful microcontroller manages the control functions, the internal functions, the network
supervision and the links with the panel or the controlling PC.
The AM41443 has 3 independent balanced outputs. The main output works through a volume
control on the front panel. The second output, also having a trimmer volume control, can serve
a separate group of amplification devices. The third output can create a chain of several
automatic mixers through a RJ45 shielded connection cable containing the audio and the
control line data.
An output group can be managed by a tri-band equalizer adjusting the curve. The input
channels can be divided into two groups for particular uses such as in broadcast applications
with ambience microphones.
This device works with 24V external batteries and can give power supply up to 5 AM41443
with no need of additional power sources.
The firmware updates available on Internet can be easily installed through the USB port.
1.3 THE PACKAGE CONTAINS
Inside the AM41443 box you will find:
1 AM41443
1 50 cm RJ45-RJ45 connection cable
1 24V 300mA power supply
1 short rack-mounting bracket (long bracket for single mount or support for double mount are
optional)

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2. DESCRIPTION
The automatic mixer preamplifier AM41443 provides all the fundamental functions typical of
such device and some more features:
•It opens the engaged microphone channels only, and keeps the others closed (see par.
4.8). In other words, when the signal is generated by the voice of the speaker talking into
the microphone, the channel opens and turns on the signal. In any other case, when the
signal is due to ambient noise or reverberation, the channel stays closed and the signal
is attenuated and not heard.
•It keeps the mixer's output level at its preset value when the number of open microphone
channels changes (see NOM App.A.5)
Besides, the following functions are also available:
•LAST-ON: last activated microphone remains open even if the speaker is silent until a
new microphone is activated
•LOM: The number of open microphones can be limited from 1 to 4 for the single device,
from 1 to N for linked devices.
•ONE-ON: Microphone channel 1 is activated when any other microphone receives a
signal
•PRIO: one microphone channel has the priority over the other microphones.
•ORG: a chosen channel forces the closing of other channels which were qualified for
this function
•OVR: A channel can be forced open
Other AM41443 features are indicated in sections 8.1-8.2
The logic controlling this device is undoubtedly its fundamental and most important
characteristic. The AM41443 is basically a mixer with a VCA on each microphone channel that
turns the microphone on and off. Normally off, the gate goes on as soon as someone begins
speaking at the relevant microphone. One of the most important problems for an Automixer is
the circuit used to turn the channel on or off. To attain this result the incoming voice signal must
be compared to a reference or threshold signal. The easiest way is the use of a fixed threshold
as in a simple gate (the threshold voltage may actually be adjusted manually but remains fixed
during operation). A fixed threshold does not work: if set low, every unwanted sound picked up
by the microphone will open the channel, if set too high the first syllable of the speech will be
lost.
What is needed is a threshold voltage that automatically follows the ambient noise. Such is the
circuit used by the Automixer where the sum of the signals picked up by all microphones
connected to it is processed to produce the reference threshold signal that represents the
ambient noise. This way what actually turns the channel on is the difference between the direct
sound and the background or ambient sound.
The managing of the functions dedicated to an automatic mixer can be various and different.
The AM41443 is an analog mixer based on a digital control and even if it has a predefined
control mechanism it is open for future implementation of alternative models for the microphone
controls.
The AM41443 features 4 variable gain microphone inputs; phantom power is given to all
microphones at the same time through a front panel switch.

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2.1 BLOCK DIAGRAM AND DESCRIPTION
As shown in the picture the AM41443 mixer can be
used in very different situations thanks to its
particular features. As already said in the
description, this automatic mixer is a digital
controlled analog device. This means that AM41443
can conceive a very high audio purity and has the
advantage to allow both a local and a remote control
on the main functions. Also other processes, as the
channels opening, can be automated following
needs.
The input section has 4 variable sensitivity inputs
and processes signals from –60 dB to line level.
These inputs can be divided into 2 blocks of 2
channels each to control separately (locally or
remotely) the mixing of a number of channels. In this
manner, for example, we can mix on the auxiliary
output all 4 channels while we send only two of them
to the general mixing. This function could be useful
in situations in which a service need ambience
signals for a radio broadcast while the preserved
signals (without the ambience) are sent to the local
reinforcement system.
A tone correction feature can be used before the
master or the auxiliary output. The daisy chain
connection of more AM41443 (up to 24 devices can
be linked) is obtained through a RJ45 connector.
This connection allows the link between the units of
the digital line for the control-information on the
chain and the analog signals producing the mixed
program. The audio signals are directional.

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2.2 AM41443 FRONT PANEL
1) AUX2 Auxiliary volume output 2) Master volume 3) Low-medium-high tone control
4) VU meter and configuration signal 5) Microphone input level 1-4 6) ON LED
7) USB connection for remote PC control 8) External control LED 9) Reset button
10) Mode and function selection switch
12 345789
10
6

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2.3 AM41443 REAR PANEL
20) DAISY CHAIN connector 21) RCA auxiliary output 22) Master output
23) RS232 port 24) DC power supply 25) MICRO-LINE inputs
26) Sensitivity/filter switch
20 21 22 23 24 2625

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3. THE CIRCUIT
AM41443 is a complete automixer-preamplifier that can drive one or more power amplifiers.
Main features:
•4 variable sensitivity microphone inputs with 48V phantom power and selectable
high pass filter (see 3.1-3.2)
•General tone control (see 3.3)
•Balanced master output on XLRm connector (see 3.4)
•Balanced auxiliary output on RCA connectors (see 3.5)
•USB control port (see 3.6).
•RS232 serial control port (see 3.7).
•Connector used to link other mixing units through a daisy chain connection (see
3.8).
3.1 FRONT PANEL SELECTION SWITCH
In the default configuration of the device all the switches are lowered. In this condition it
works as an automatic mixer. To be more detailed:
The first lowered switch shows that the device is operative in the automatic mode, while all
the other functions are deactivated. These functions can be activated putting switches no. 2-
3-4-5 in the ON position.
For example:
to activate LAST-ON push switch no. 3 upward.
to activate phantom power on all microphones put switch no. 5 in the ON position.
The first switch in the ON position shows that the device is in the manual mode, i.e. mixing
every signal without on-board intelligence (as a concert mixer). The other functions (Noise-
Gate, Future Use, Limiter, and Phantom) can be activated pushing the switches upward
N.B. The first switch position changes the meaning of 2nd and 3rd switch.
AUTOMIXER
1
2
3
4
5
PHANTOM
LIMITER
LAST-ON
PRIO-CH1
ON
OFF

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P.S. The AM41443 can be controlled through an external serial connection (see
software user’s manual for the control of AM41443). It is important to remember that
the settings activated from the front panel prevail on the ones given from an external
control.
3.2 MICROPHONE CHANNEL
It includes the balanced input low noise preamplifier with selectable sensitivity control and
high-pass filter.
The microphone input features a XLR-3F connector codified as follows:
PIN 1 = MAINS / PIN 2 = + (hot) / PIN 3 = - (cold)
Next to the XLR connector there is a 4-position DIP-Switch [26, par.2.4]. The three sections
on the right control the gain following the scheme in the picture.
1
2
3
4
5
MANUAL
MIXER ON
OFF
PHANTOM
LIMITER
(FUTURE USE)
NOISE-GATE

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The gains increase lowering the switches from right to left as shown here above and on the
device rear panel.
HIGH PASS FILTER
HIGH PASS FILTER ON 100HZ
FLAT
(flat up to 10 Hz)
The first section on the left is for the activation of the high pass filter. This filter is activated as
in the above scheme:
The installer must necessarily know the exact sensitivity of the installed microphones
in order to assign the correct gain to each input.
The green LED (par.2.3) placed on the front panel under every volume control lights up when
a channel is activated. When the light goes out the channel is being deactivated. In case of
short pauses the led stays on, due to the HOLD circuit.
When this LED lights up in RED colour it indicates the channel is saturated. If the LIMITER
function is activated, this LED indicates that the limiting function is active on the signal to
avoid the saturation.
1 2 3 4 1 2 3 4
1 2 3 4 1 2 3 4
0dB
40dB
20dB
60dB
1 2 3 4
1 2 3 4