Digidesign ADAT Bridge I/O

Digidesign's new interface allows Pro Tools users to transfer data to and from ADAT‑compatible devices. Mike Collins finds out if it's a Bridge too far...

The ADAT Bridge I/O is Digidesign's latest addition to the wide range of peripherals available for Pro Tools systems, and enables the user to transfer simultaneously up to 16 tracks of ADAT data in either direction between a Pro Tools system and two ADAT‑compatible devices. Bridge I/O works with Pro Tools 24, Pro Tools III or Pro Tools Project PCI systems using Pro Tools v4.1.1 (or higher) software. As ADATs are 8‑channel devices, the unit manages its I/O in two separate 8‑channel Groups, A and B. You can connect two ADATs to each ADAT Bridge I/O, and up to five ADAT Bridge I/Os can be used with Pro Tools for a maximum of 72 channels of input and output. The ADAT Bridge connects to your Pro Tools card in exactly the same way as an 888 or 882 interface, using a multiway cable running from the back of the unit to the computer card. If you already have an interface connected you can connect to the DSP Farm card instead, and if you have two interfaces already, you can use a special Y‑cable (which Digidesign can supply) to connect two interfaces to one socket on the back of the card.

Judging By Appearances

Looking from the left of the front panel, the On/Off switch is followed by four pairs of Sync Mode LEDs. Group A (channels 1‑8) and Group B (channels 9‑16) each have their own set of LEDs to indicate the sync mode. This will be 'Internal' when using the internal clock, 'ADAT' when slaved to an ADAT, 'Digital' when slaved to AES‑EBU or S/PDIF, or 'Slave' when referenced to an external clock signal. Two pairs of LEDs near the centre show whether Pro Tools' channel 1‑2 inputs for Group A or B are receiving from the ADAT ports or the AES‑EBU or S/PDIF ports. You also get two pairs of LEDs to indicate whether the current sample rates of Group A and Group B are 44.1 or 48kHz. A final pair of LEDs indicate which digital port, AES‑EBU or S/PDIF, is currently being used for digital input on channels 1‑2 of Group A or B. All very straightforward and easy to get to grips with.

On the back panel, looking from the left, there is a pair of analogue outputs via balanced quarter‑inch TRS jack sockets, which feature 20‑bit D‑A converters. The outputs are software‑switchable for ‑10dBV or +4dBu operation, and by routing your Pro Tools mix to outputs 1‑2 you can use them to monitor your entire mix. Two pairs of ADAT optical input and output connectors are provided, one for each Group, and there are two Computer ports which you use to connect the interface to a Pro Tools d24 card, DSP Farm, or Disk I/O card. To the right of these there is a pair of AES‑EBU balanced XLR connectors, followed by a pair of unbalanced phono S/PDIF connectors — both of which can carry digital data in and out at up to 24‑bit resolution. Again, these carry whatever signals you have routed to output pair 1‑2 in Pro Tools. A pair of BNC 'Slave Clock' in and out sockets are provided for Digidesign's 256 x word clock (often referred to as super clock) and these may be used for slaving from or to additional ADAT Bridges, audio interfaces or sync peripherals. A single Word Clock Out BNC is also provided to let you connect the ADAT Bridge to a BRC or other sync device which requires this type of clock signal. Finally, at the far right there is a Euro‑connector for the mains supply.

In Use

The most obvious use of the ADAT Bridge I/O is to transfer up to 16 tracks of digital audio simultaneously from ADAT into Pro Tools. This is a great way to work with your ADAT tracks, allowing you to use Pro Tools' non‑linear editing, TDM effects processing and digital mixing with automation. You can go the other way as well, transferring 16 tracks at a time from Pro Tools onto ADAT to replace original tracks with edited tracks. This also provides an affordable means of backing up Pro Tools tracks on to S‑VHS tapes, and a convenient way of transferring Pro Tools tracks to another Pro Tools/ADAT system. You can simply hook up the ADATs to Pro Tools, start Pro Tools recording and then press play on the ADATs to record tracks into Pro Tools — or vice versa — though this way there is no sync between Pro Tools and the ADATs. For proper sync, with better than quarter‑frame accuracy, you need an external sync device. Probably the cheapest solution is the JL Cooper DataSync 2 which translates the proprietary ADAT ABS time‑reference signal embedded in ADAT tapes into MTC. With a DataSync 2 and a MIDI interface, ABS is converted to MTC and used to trigger Pro Tools using the ADAT's transport. A second alternative is the MOTU Digital Time Piece which also features ADAT sync along with many other sync types. Alternatively, the ADAT BRC can be used as both a transport and clock master for Pro Tools and the ADAT to achieve synchronised track transfers. Yet another possibility is to use the ADAT ports to connect Pro Tools to a Yamaha 02R or 03D, Mackie 8‑buss or other compact digital mixer at 20‑bit resolution. In this case you can synchronise the mixing console's sample rate to the Word Clock output from the ADAT Bridge I/O. You can also use the ADAT Bridge I/O as a stand‑alone S/PDIF or AES‑EBU to ADAT‑optical converter so you can transfer audio digitally from DAT or CD to ADAT without having to power on your computer or launch Pro Tools.

Final Word

The ADAT Bridge I/O proved to be ideal for use in my project studio along with my existing 888 interface, allowing me to connect 24 tracks from Pro Tools to my 02R. In this setup I used a DTP as the transport and clock master, feeding super clock to the ADAT Bridge I/O and word clock to the 02R. The ADAT Bridge I/O performed flawlessly, and I can highly recommend it to anyone with similar requirements.