bel Digital Audio BM-A1-16OB User manual

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BM-A1-16OB
16 Channel Digital Audio Monitor
User’s Guide

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BEL (Digital Audio) Ltd., has made every effort to ensure the accuracy of information contained within
this document, which is nevertheless supplied for information purposes only and does not constitute any
form of warranty or guarantee.
All trademarks acknowledged.
The information in this document is subject to change without notice.
Bel (Digital Audio) Ltd.
Unit 3
Horwood Court
Bletchley
Milton Keynes
Bucks
MK1 1RD
United Kingdom
Tel: [phone]
Email: [e-mail]
Web: www.beldigital.com

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Contents!
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Introduction!............................................................................................................................................!4!
Main!features!..........................................................................................................................................!5!
Front!panel!rotary!controls!.....................................................................................................................!6!
Operation!................................................................................................................................................!7!
Selecting!sources!.................................................................................................................................!7!
SDI!input!mode!...................................................................................................................................!7!
Directing!sources!to!speakers!.............................................................................................................!7!
Status!display!..........................................................................................................................................!7!
Rear!panel!inputs!....................................................................................................................................!8!
Rear!panel!outputs!..................................................................................................................................!8!
Menu!.......................................................................................................................................................!9!
Top!level!menu!page!...........................................................................................................................!9!
Line!level!output!adjustment!............................................................................................................!11!
Installation!............................................................................................................................................!12!
Specifications!........................................................................................................................................!13!
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Introduction!
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The BM-A1-16OB is a 1U high-quality sixteen-channel audio monitor with multiple I/O as
standard. Designed in a compact 200 mm depth chassis, ideal for outside broadcast
applications, the unit accepts audio from any one of four AES input pairs, two analogue inputs
or one of two SDI inputs and produces four pairs of AES outputs and one pair of analogue
monitor outputs. The SDI inputs automatically detect SD or HD or 3G video and de-multiplex
all 16 audio channels. An active loop-through output is available for the SDI input selected.
The headphone output mutes the speakers when used. Eight high-resolution tri-colour
bargraphs are provided with user-selectable ballistics and colour break points. Up to sixteen
channels can be selected individually or mixed and directed to each speaker.
Bargraph meters are arranged in two groups of eight, they can display 1 to 8 or 9 to 16 using
the select button under the status display. Stick-on graticule scales, which may be applied to
the spaces between the front-panel bargraphs, are supplied with the machine.
The first eight audio channels are provided at the rear of the unit as four pairs of AES signals.
The analogue outputs can be at a fixed level or slaved to the front panel volume control. The
analogue outputs can also be muted independently from the menu or under the control of
the front panel mute switch.

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Main!features!!
 Compact 200 mm depth chassis, ideal of OB/flyaway applications
 Four pairs of unbalanced (BNC) digital audio inputs (AES3id)
 Two auto-sensing SD/HD/3G inputs with regenerated loop-through
 Two balanced analogue inputs (XLR)
 Two groups of four tri-colour bargraphs (selectable between ch1-8 and 9-16)
 Analogue monitor line outputs, four pairs of AES3id outputs
 Headphone connector with speaker mute
 Three speaker system with dedicated LF driver
 Stainless steel chassis

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Front!panel!rotary!controls!
Volume
The volume of the speaker and headphone output can be adjusted using this control.
Volume level is indicated on the Status Display. Pressing the end of the control will mute
the speaker audio. This can also mute the analogue outputs.
Balance
This control will differentially adjust the level of the speaker and headphone output.
Pressing the end of this control will centre the audio output.
Menu
Pressing the end of this control will enter the menu mode described in the Menu section.
Input select
Rotating this control will select one of the four audio input sources; Analogue, AES, SDI1
or SDI2.

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Operation!!
Selecting!sources!!
The input source select switch determines which source (Analogue, AES, SDI 1 or SDI 2)
is available to the speaker selectors and bargraphs. AES inputs can be from 44.1 kHz to
96 kHz sampling rate.
SDI!input!mode!!
The unit automatically detects SD, HD or 3G video. The four SDI groups will be demuxed
to give 16 audio signals.
Directing!sources!to!speakers!!!
Where more than two audio signals are present it may be useful to direct and combine
sources to selected speakers. The left speaker is indicated by a red LED and the right by a
green LED on the top of the bargraphs.
To direct a particular source to the left or right speakers proceed as follows:
Repeatedly press the button under the bargraph corresponding to the input audio signal
required until the top LEDs of the bargraph shows red for the left speaker, green for the
right or both to direct the audio to both speakers. Each speaker can receive a mix of audio
from inputs 1 to 16. Select either lower or upper 8 sources using the select button.
Note that the mix button assignments are retained over power-down.
Status!display!!
The Status display will show general status information related to the currently selected
input such as the source selected and video standard where applicable. It also displays on
the bottom row the volume level as a horizontal bar.
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Rear!panel!inputs!
The BM-A1-16OB accepts SDI video, AES and analogue audio inputs. Two balanced
analogue inputs are provided on XLR connectors. Four pairs of AES3id unbalanced inputs
are also available on BNC connectors. Two SD, HD, 3G auto-select SDI inputs are
provided on BNC connectors.
Rear!panel!outputs!!
The BM-A1-16OB provides both digital and analogue audio outputs on the rear panel. The
audio carried on the AES outputs are derived from the currently selected input source
(analogue, AES or SDI). In effect, these audio outputs are a copy of the signals shown on
the unit’s bargraphs (channels 1-8). Two balanced analogue monitor outputs are provided
which carry the same audio as the speakers. The levels of the analogue outputs can be
configured to either be fixed or adjustable via the front panel volume control in the menu. It
is possible to mute the output from the unit’s speakers by pressing the end of the VOLUME
control. It is also possible to independently mute the analogue outputs, either via the volume
control or by muting it using the menu.
An SDI loop-through is available which carries a reconstituted SDI signal from the currently
selected SDI input.
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Menu!
Many of the characteristics of the BM-A1-16OB can be adjusted in the menu. When the
menu is activated, by pressing the NAV rotary encoder, the top level of the menu will
appear. The items in this level can be selected by rotating the encoder and then pressing
it for approximately 0.5 seconds. The second level will then appear and the required item
selected by rotating the encoder and then pressing it. At this point in the menu the value
of the current parameter can be adjusted. To go back one step in the menu press and
hold the encoder for longer than 1 second.
Tip: Simultaneously pressing the buttons under the bargraphs 7 and 8 will completely exit
the menu.
The characteristics that can be adjusted in the menu are shown below.
Top!level!menu!page!
The top level of the menu carries the main areas of operation of the BM-A1-16OB that
can be adjusted.
1. Level meters - This section allows access to the bargraph colour break points and
ballistics.
2. Line levels - The analogue output level control can be selected here (either fixed level or
controlled by the volume control). The analogue output can also be muted, or slaved to
the main speaker mute control.

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Level!Meter!Adjustment(
Various aspects of the audio level indication can be adjusted here.
1. Amber threshold - The point at which the bargraph changes from green to amber can be
adjusted here. Bargraph 16 is forced to full scale to allow easy control of the colour
transitions.
2. Red threshold - The point at which the bargraph changes from amber to red can be
adjusted here. Bargraph 16 is forced to full scale to allow easy control of the colour
transitions.
3. Ballistics - The scales and dynamics of the bargraphs can be selected here. The options
are AES, DIN, VU and BBC. The appropriate scales should be affixed to the front panel.
4. Analogue offset - When an analogue input is selected and the bargraph ballistics are
AES the way in which this is displayed is adjusted here. If 0 dB analogue is applied to the
unit the bargraph can be configured to show either -18 dB or -20 dB.
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Line!level!output!adjustment!
The audio currently selected for the two front panel speakers is also available on two XLR
connectors on the rear panel. The level of these can be adjusted from this menu.
1. Line level - The line output level can be fixed or controlled by the front panel volume
control and this can be selected here.
2. Fixed line level - When fixed output level is selected its level can be adjusted here.
3. Line mute - The line outputs can be muted here or the mute can be slaved to the front
panel volume control.
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Installation!!
The BM-A1-16OB is designed to be installed in 19" bays on an equipment tray.
Ventilation is by natural convection.

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Specifications!!
Audio inputs
Digital AES3id 4 x 75 ohm (BNC connector). Sample rate 44.1 - 96 kHz.
Analogue 2 differential XLR. Clipping +15 dB
Audio outputs
Digital AES3id 4x 75 ohm (BNC connector) sample rate 48 kHz.
Line output Copy of speaker outputs, level adjustable on 2 x XLR3M
connectors.
Analogue noise Noise+THD: -108 dB w.r.t clipping
Analogue frequency response: 20 Hz to 20 kHz ±1dB
Video inputs
Video format 2 x 32/HD/SD – auto-sensing (BNC)
SMPTE 424M, 259M, 296M, 274M, 292M
Video output
1 SDI active reclocked loop-through (BNC connector).
Main drive amp
Noise +THD -80dB w.r.t. maximum output.
Speaker driver units
Peak acoustic level (@2ft) 100 dB SPL
Shielding Magnetic

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Meters
Tri-colour LED bargraphs with adjustable colour break points and ballistics.
DIN PPM: Overall dynamic range: 55 dB (+5 to -50 dB)
Attack time: 10 mSec
Fallback: 1.5 Sec per 20 dB decay
BBC PPM: Overall dynamic range: (+12 to-12 dB from mark 7 to mark 1)
Attack time: 10 mSec
Fallback: 2.85 Sec (from mark 7 to mark 1)
VU: Overall dynamic range: 23 dB (+3 to -20 dB)
Attack time: 300 mSec
Fallback: 300 mSec
AES/EBU: Overall dynamic range: 60 dB (0 to -60 dB)
Attack time: 1 mSec
Fallback: 1.5 Sec per 20 dB decay
Dimensions
19” Rack Mount: 1U high.
Outline Dimensions: 483 mm(W) x 200 mm(D) x 44.3 mm(H)
Outline Dimensions: 19 inch(W) x 7.87 inch(D) x 1.75 inch(H)
Environmental
Temperature 0° C to 30° C Humidity 70% max (non-condensing)
Weight
4kg (8.8lbs)

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