INDEPENDENT MEDIA

Yamaha D24 MO Disk-based High-resolution Digital Multitracker

Published in SOS May 2000
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Reviews : Multitrack Recorder

The eight-track digital recorder has become a standard building block at virtually every level of the recording industry, and a wide range of tape and hard disk-based devices is available. Now Yamaha have extended the choice with a machine built around a 640Mb magneto-optical drive. Hugh Robjohns takes it for a spin...

The concept of the Modular Digital Multitrack or MDM has been widely adopted across the professional and semi-pro recording industry. It all started back in the early 1990s with Tascam's DTRS and Alesis's ADAT formats. DTRS has become the mainstay within professional circles whereas ADAT reigns supreme in the MI business, and both formats have been adopted by other manufacturers -- Sony in the case of DTRS and Studer for ADAT. Both of the original systems have also seen upgrades to higher resolutions recently.

However, ADAT and DTRS are far from being the only MDM formats on the market. It seems that virtually every significant pro audio manufacturer has something similar to offer, and many are based around hard-disk formats rather than tapes -- for example, the DAR, Genex and Akai systems, to name just three. Yamaha have recently joined this competitive marketplace with their own contribution, the D24 Digital Multitrack Recorder.

Optional Interfaces     The mini YGDAI interface cards used in the D24 are already proven in the O1V digital console, but are different to those employed in the O3D and O2R consoles and are not interchangeable. Analogue inputs and outputs are catered for with the MY4DA, MY4AD and MY8AD, providing four-channel D-A and A-D and eight-channel A-D conversion respectively. The four-channel cards feature electronically balanced XLRs and 24-bit converters whereas the eight-channel card employs TRS quarter-inch sockets and 20-bit converters. All have adjustable gain structures through slide switches on the circuit cards. The MY4AD offers three possibilities with 0dBFS aligning to either +4dBV, +18dBu or +24dBu -- configurations optimised for -10dBV, +4dBu and +10dBu environments, respectively. The MY8AD card provides two alignment options, +24dBu and +4dBV, and the D-A module is provided with similar slide switches to select the nominal operating level to suit +4dBu or -10dBV environments (0dBFS digital peak equating to +18dBu or +4dBV, respectively). Three digital interfacing options are available with ADAT and TDIF formats as well as AES-EBU, all carrying eight channels of I/O supporting 16-, 20- or 24-bit resolution. The MY8AT card provides a pair of ADAT light-pipe ports for input and output, while the MY8TD TDIF version is fitted with a 25-pin D-sub connector and BNC word clock output. The AES-EBU interface on the MY8AE card requires a special breakout cable to access the eight inputs and outputs from a 25-pin D-sub connector. When recording at the elevated sample rates of 88.2 or 96kHz, the four audio tracks are made available in the double-fast format over the AES-EBU interface: the AES-EBU connector normally associated with tracks 1 and 2 carries only Track 1, outputs 3 and 4 carry track 2, and so on. Analogue or digital inputs are installed in YGDAI slots 1 and 2, whereas slots 3 and 4 are for analogue output cards. I set the review machine up with an ADAT card in slot 1 and an MY4AD in Slot 2 (the MY8AD was not available). Slots 3 and 4 carried MY4DA cards to provide eight analogue outputs in addition to the eight digital ADAT outputs.

The rear panel contains a wealth of interfaces, including four slots for optional mini-YGDAI cards. The top row includes video and word clock interfaces (both with In and Through sockets, plus termination switches), a trio of MIDI sockets, a 50-pin half-pitch SCSI port (see SCSI box), an RS422 9-pin serial port, and a pair of 15-pin D-sub sockets labelled Remote/Sync In and Sync Out. These are used to interface the optional remote-control unit, and also to connect multiple D24s together in various configurations using 15-pin sync cables.

The lower left quadrant contains a reasonably quiet cooling fan along with the usual IEC mains inlet, timecode In and Out sockets (on XLRs) and a pair of S/PDIF digital I/O connectors. These can be assigned to individual pairs of tracks, all tracks (allocated on a left-odd, right-even basis), or turned off completely. The S/PDIF input accepts 16-, 20- or 24-bit signals, as determined by the current project settings. However, there is no facility to redither 24-bit input signals if you are recording at 16-bit, for example, and care must be taken to set the correct dithering options at source. The S/PDIF output resolution is the same as that of the recording, and it is disabled for elevated sample rates.

The D24 supports all the usual timecode formats including 24, 25, 30-drop and non-drop frame rates. It contains its own internal timecode generator but can also slave to external timecode or timecode via the Remote/Sync-In connector, as well as accommodating MIDI Time code (MTC). The synchronising timecode source (internal or external) is also output through the same array of ports, including MTC, and with an offset if required.

Four slave chase modes provide a continuous chase lock, a sync and free-run operation, and two variations on this last mode which cause the transport to stop if the code becomes unreadable for either 1 or 2 seconds. These modes are very useful, for example, when the master timecode disappears during tape shuttling. Under this condition, the continuous chase-lock mode will abort and stop the transport, whilst the free-run mode will carry on regardless! The two last modes, however, will stop and then resync as soon as stable code appears.

The bulk of the rear panel is given over to four removable blanking plates, permitting a variety of analogue and digital interfaces to be installed. These mini-YGDAI cards (as used in the O1V digital mixer) are fitted easily into side rails and retained by thumbscrews. See the Optional Interfaces box for more information.