Project Description

DirectOut Technologies EXBOX.BLDS

Automatic, seamless MADI changeover switch for fail-safe applications.

  • 2-in/2-out MADI changeover switch for critical audio playback or broadcast routing applications
  • Automatically selects secondary MADI source if primary source fails
  • Alternative manual source selection from either front panel or via GPIs
  • Two modular MADI ports: either may be fitted with BNC coaxial, SC optical or SFP carrier in any combination
  • Uses proprietary BLDS (Buffer Loop Detection Signal) as trace tone to confirm presence/validity of incoming MADI data
  • Software application (supplied) generates a BLDS audio file to be imported onto a spare DAW track
  • Can be configured to switch on loss of BLDS or MADI frames
  • Switches within 2 samples (0.02 ms @ fs=96 kHz) of BLDS failure detection
  • MADI data is reclocked
  • Second (parallel) output for monitoring purposes
  • Supports sample rates up to 192 kHz
  • Seamless, inaudible changeover when sources are wordclock-synced
  • Supports all MADI formats: 56/64 channel, 48k/96k frame, S/MUX 2/4
  • LEDs confirm MADI and/or BLDS statuses
  • User-definable priority operation
  • USB port for remote control and firmware updates
  • 4 x GPI port, 4 x GPO port for signalling and control
  • Dual power supply inputs for redundancy
  • Compact free-standing unit; optional rackmount frame available for three EXBOX or MA2CHBOX.XL units

The EXBOX.BLDS is a development of the EXBOX.64, which provides MADI re-clocking, optical/coaxial format conversion and can act as a MADI extender.


The EXBOX.BLDS has been developed to provide an automatic, inaudible changeover between two identical, synchronised MADI sources in the event of the failure of one of them. Typical applications would be the use of two DAWs for multitrack audio playback at large-scale musical events, or two (differently-routed) MADI feeds at a large OB site.

DirectOut Technologies has developed the Buffer Loop Detection System (BLDS) as part of the solution to fail-safe, dual-redundant MADI operation. A specially-developed data pattern is transmitted on one channel of each MADI stream (usually Ch 56, or Ch 28 if 96 kHZ sample rate is in use) at low level (-66 dBFS). This can be generated by a simple Windows application (available as a freeware download) and imported as an audio file to one DAW track.

The EXBOX.BLDS constantly monitors the data channel on the primary input and in the event of a data discontinuity, automatically re-routes the output MADI datastream to be sourced from the secondary input. Changeover typically occurs within 2 samples, and provided the source audio is identical and the DAWs (or other MADI sources) are externally synchronised via a common timecode source, the output audio will be seamless and the changeover inaudible.

Manual operation is also available, with a front panel button “forcing” selection of one MADI input; source selection may also be controlled remotely via the GPI port.

MADI I/O on the EXBOX.BLDS is modular. Each of two independent ports can be fitted with any of three I/O module types: a coaxial module with two BNC sockets, an optical module with a standard dual SC optical connector (either singlemode or multimode), or an SFP module with an SFP carrier, which may be fitted with either a singlemode or multimode cartridge with LC connectors, or a dedicated MADI cartridge with a mini coaxial connector.

MADI Out 2 always provides a buffered and reclocked copy of the data at MADI Out 1; this is useful for local monitoring/checking of the output datastream.

A comprehensive set of front panel LEDs confirms the status of incoming MADI and BLDS signal on each port, priority settings and clock status. Separate 9-pin GPI and GPO ports allow remote set-up and monitoring. The 4-input GPI port permits manual selection of one input and priority set-up, while the 4-output GPO port provides unit status tallies for remote signalisation use.

The EXBOX.BLDS is built in a compact metal enclosure (140 x 140 x 42 mm) and is supplied with two external DC PSUs, which connect via separate, locking rear panel HiRose connectors. A 19” adaptor is available, which permits up to three units of the same size (the EXBOX range and the MA2CHBOX.XL) to be rackmounted.

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