Basic operation of the AR-DM21 Audio Monitor involves selecting an input module as the audio source, monitoring signal presence using 16 LEDs, and choosing a mode in which to monitor audio through the stereo speakers. The user can switch between up to four installed I/O modules, each providing up to 16 channels of audio. The 16 Channel Presence LEDs immediately display signal presence for all channels. Finally, audio channels from the selected module can then be monitored through the stereo speakers in a variety of ways: Any single channel can be monitored in mono, any channel pair can be monitored in stereo, and any group of eight channels can be down-mixed to stereo using a variety of configurations.


16 Channel Digital Audio Monitor – 1RU Mainframe

Owner's Manual (PDF) Spec Sheet (PDF)
16 Channel Digital Audio Monitor 1RU Mainframe

  • Only 1RU (1.75")
  • 16 LED Indicators for channel presence
  • User-configurable with a variety of modules
  • 100% Digital Processing
  • Class D Audio Amplification
  • Dolby® Digital / Dolby® E Decoding (with optional ARDM-D552 module)
  • Selectable Stereo Downmix Modes
  • USB 2.0 Port enables on-site firmware upgrades
  • Ethernet port allows remote alarm monitoring
  • Balance and Volume Control
  • 1/4" Headphone Jack

The AR-DM21 is ideal for TV facilities, studios, post production, VTR bays, mobile production vehicles, satellite links, and wherever multichannel audio monitoring is required. The AR-DM21 supports 16 audio channels with four slots available for interchangeable input / output modules. This unit also provides pristine audio quality and unrivaled flexibility with 100% digital processing, Class D (digital) amplification, selectable stereo downmix modes, Dolby® Digital / Dolby® E decoding capability (with optional ARDM-D552 module), a ¼” headphone jack with Level control, and an RS-485 port for on-site firmware upgrades.

The AR-DM21 also provides LED indicators for monitoring signal presence and system status. Both VU and peak metering are supported. Channel, Group, Mix, Dolby®, and Balance selection, and saved configurations are easily accessed via the system’s large navigation buttons. For audio playback, the AR-DM21 provides two magnetically-shielded loudspeakers in a compact 1RU design.

Marshall Electronics 16 Channel Digital Audio Monitors are equipped with features to help broadcasters comply with CALM and EBU loudness regulations. The monitors provide timely visual and audio alerts, email notifications and complete logging of noncompliant signals.

Multi-Rate SDI/HD-SDI Video InputARDM-HDSDI
  • Multi-Rate SDI/HD-SDI Video Input (Auto-Detect)
  • Re-Clocked SDI/HD-SDI Loop-Through Output
  • SDI: SMPTE 259M-C / HD-SDI: SMPTE 292M
  • Supports 8 Stereo Embedded Channels or Dolby®
  • Multi-Channel Decoding*

4 Unbalanced AES/EBU Inputs (BNC)ARDM-AES-BNC
  • 4 Unbalanced AES/EBU Inputs (BNC)
  • 4 Passive Loop-Through Outputs (BNC)
  • Supports 4 Stereo Channels or Dolby® Multi-Channel Decoding*
4 Balanced AES/EBU Stereo InputsARDM-AES-XLR
  • 4 Balanced AES/EBU Stereo Inputs (DB-25)
  • 4 Passive Loop-Through Outputs (DB-25)
  • Break-Out Cable included (DB-25 to 8 XLR)
  • Supports 4 Stereo Channels or Dolby® Multi-Channel Decoding*
8 Balanced Analog Audio InputsARDM-AA-8XLR
  • 8 Balanced Analog Audio Inputs (DB-25)
  • Nominal level: 0,+4,+6, or+8 dBu = -20dBFs
  • Break-Out Cable included (DB-25 to XLR)
2 Balanced Analog Audio OutputsARDM-AA-2OUT
  • 2 Balanced Analog Audio Outputs
  • Nominal level: -20 dBFs = +8 dBu
  • Excellent for on-the-fly 2-channel monitoring
4 Unbalanced AES/EBU OutputsARDM-AES-4OUT
  • 4 Unbalanced AES/EBU Outputs (75Ω BNC)
  • Capable of 4 AES/EBU Outputs
    De-embedded from HD-SDI or SD-SDI input
  • Capable of 4 AES/EBU Outputs Decoded
    from Dolby® E / Dolby® Digital bitstream*
Requires optional Dolby® E / Dolby® Digital Decoder Module (ARDM-D552)

Dolby E/Dolby Digital Decoder Module


Dolby® E/Dolby® Digital Decoder Module
Required for multi-channel decoding

Dolby and the double-D symbol are registered trademarks of Dolby Laboratories

AR-DM21 specifications
HDSDI Input Module Dolby Support ARDM-D552 Module
1/4" Headphone Jack Yes
16 LED Indicators for channel Yes
Internal Speakers Yes
Modular Input Slots 4
Self-Sensing Yes
1 x SDI 75Ω BNC 16 Channels Embedded Audio
PCM,Dolby E, Dolby Digital AC3, Yes
Video Formats 525i, 625i, 720p, 1080i, 1080p
De-Embedded from SDI Yes
Sample Rates: 44.1kHz, 48kHz
Unbalanced 75Ω BNC 4 x AES/EBU Inputs
Unbalanced 75Ω BNC 4 x AES/EBU Passive Loop Outputs
Formats Professional and Consumer (SPDIF)
AES BNC Module PCM,Dolby E, Dolby Digital AC3, Yes
AES XLR Module 4 x AES/EBU Balanced 110Ω DB-25 Connector
Formats Professional and Consumer (SPDIF)
PCM,Dolby E, Dolby Digital AC3, Yes
Sample Rates: 44.1kHz, 48kHz
AA-8XLR Module 8 x Analog Balanced XLR DB-25 Connector
Reference: 0, 4, 6, or 8dBu = -20dBFS Selectable
DB-25 Pinout: GOLD-DB25-XLR-05 Break-Out Cable
AES 4 Out Module Output 4 x AES/EBU Unbalanced 75Ω BNC
Formats Professional and Consumer SPDIF
Audio Coding: PCM,Dolby E, Dolby Digital AC3,
Sample Rates: 44.1kHz, 48kHz
AA-2 Out Module Outputs 2 x Analog Balanced XLR
Reference: -20dBFS = 8dBu
Control Features Volume Control Yes
Balance Control Yes
Ethernet Yes
Memory Stick Upgradable Yes
Mute Functions Yes
Controls on front Panel Yes
SRC Switch Selector Yes
Handles Yes
Power Voltage 24 VDC
Consumption Less than 45W
Connector 4Pin XLR
Rack Unit dimensions 18.94” x 1.75” x 7.80
Weight (Main Body) 3.7 lbs

* Pricing does not reflect freight costs and applicable taxes and duties
* Pricing, specification and features are subject to change


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