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Fostex D90

Hard Disk 8-track Recorder By Paul White
Published August 1997

Fostex take their stand‑alone 8‑track hard disk concept onward and upward, turning the well‑received D80 into the D90 with some useful and welcome enhancements. Paul White is d‑lighted...

It seems that a lot of people would like to make the transition from tape to tapeless recording, but some perceive the computer environment as over‑complicated or unreliable. Though numerous other companies produced stand‑alone hard disk multitrack recorders before Fostex did, Fostex were one of the first to address this problem in a way that was both straightforward and affordable, making their DMT8 multitracker (reviewed SOS December 1995; VL version update December 1996) and the D80 stand‑alone 8‑track recorder (reviewed SOS June 1996) popular with those who wanted solid performance on a tight budget. The new D90 is not a revolutionary product, but rather evolutionary, in that it builds on the success of the D80 by adding new user options and features, an ADAT interface and a removable drive system. Multiple D90s may also be locked together when more tracks are needed. It can record on all eight tracks simultaneously and has comprehensive MIDI options, including integral MTC generation for sequencer sync purposes. As with the other machines in the range, recording is 16‑bit at 44.1kHz without any form of data compression, and in this model, there's also the option to work at 48kHz (for use with ADAT), and to varispeed the machine by up to 6% in either direction.

The D90 Package

The D90 is a 3U, rackmount 8‑track recorder capable of recording or replaying up to eight tracks at once using an 850Mb, IDE hard drive as a storage medium. On this model, the drive is fitted into a removable tray for easy replacement and an optional 1.3Gb drive provides up to 30 minutes of recording time; the standard drive gives around 20 minutes of recording. Other recommended drives are listed in the manual, the largest being a little over 2.6Gb.

The drive bay itself is located on the front panel of the main unit, and the control panel, which also includes metering, is detachable. Using optional multicore extensions, the control panel may be used up to 10 metres from the main unit. Unbalanced phono inputs and outputs are provided as standard, and there's a pair of ADAT optical ins and outs as well as the usual MIDI In, Out and Thru sockets. Two blanking panels on the rear of the unit may be removed to fit a SCSI option (25‑way 'D'‑connector) and a set of electronically balanced analogue ins and outs on XLRs. Using the SCSI option, any suitably specified external SCSI drive, either fixed or removable, may be used for loading and storing data.


Like previous Fostex hard disk recorders in the series, the D90 operates as a virtual tape machine, in as much as that the maximum recording time assumes that all eight tracks will be used — you can't, for example, record for twice as long by restricting yourself to four‑track recording. The space on the disk is sub‑divided into a maximum of nine 'projects', each of which may be of any length, with the proviso that their combined length does not exceed that of the total recording time. Each project would normally be used to record one song and, in addition to the audio, locate points and other data are also stored.

Fostex still persist in calling their D‑series machines non‑destructive digital recorders, but this isn't strictly true. Unlike more sophisticated systems that use a playlist system, when data is copied, moved or deleted in the D90, it really is copied, moved and deleted, just as it would be on a tape machine. In other words, if you want to use the same chorus ten times in a song, you have to make nine further copies of the original in the desired locations, overwriting anything that was previously at those locations. This simplifies operation, but doesn't conserve disk memory as well as playlist‑based systems. The majority of functions can be undone if they don't work out, providing there's sufficient disk space left for the machine to create an undo file, and I assume that this is what Fostex mean by non‑destructive. As with the D80, the editing functions are pretty basic by digital standards, but they do allow most musicians to achieve the majority of what they're ever likely to want to do without undue complications.

For all practical purposes, the recording quality is as good as DAT or ADAT, punching in and out is seamless, and the most commonly executed functions are reasonably straightforward.

Basic editing revolves around copy and paste, move and paste, cut, and erase, all of which may be referred to absolute time, MTC or MIDI bar and beat locations — the latter providing you're using the tempo map facility. Data being copied or moved is handled by a clipboard system, which, as far as I can deduce, stores the in, out and track number details of the source material rather than the material itself. Undo cancels the last edit, and Redo cancels the last Undo!

Backing up is a major concern when using hard disk systems, but in this case, data may be stored to a DAT machine (the machine must have an optical digital interface or an S/PDIF interface, plus a Fostex COP1 optical to S/PDIF converter); to an ADAT; or, if the SCSI interface is fitted, to a removable drive. Backed‑up material may then be loaded back into Programs 1‑9 of the internal drive — Programs are really just convenient ways to keep all your songs, and their settings, separate and safe from being overwritten.

User Interface

All the controls are to be found on the detachable front panel, though this may be left in place if remote operation isn't required. A large custom fluorescent display presents metering for all eight channels, along with a time readout and edit information, while a jog/shuttle dial aids location and cueing. For the most part this is effective, but some of the displayed text is difficult to read, and often contains substitute characters when the display can't manage to create the letter it needs. For example, MTC comes out as a lower case 'n' with a bar over it in place of the M — hardly intuitive.

The shuttle part of the dial provides up to 20x normal speed cuing in seven speed steps, and the jog section provides digital scrubbing for locating precise edit points without changing the pitch of the monitored sound. Parameters may also be recalled and data entered via this dial. Obviously a hard disk machine can locate to any point in a recording within milliseconds, but to retain an analogue feel the D90 'fast winds' at 30x play speed, and there's also a 5x cueing facility accessed by pressing both Play and Wind/Rewind. Punching in and out may be manual or automated, but for me the rear‑panel footswitch jack, enabling an optional footswitch to be used for hands‑off punch in/out, provides the most friendly way to work. As you'd expect, punching in and out is both seamless and gapless.

An important benefit of the D90 is that, in addition to the analogue inputs, it can also record data from a digital source via the optical interface, and both ADAT and optical S/PDIF data can be accommodated. The machine supports both 44.1kHz and 48kHz sampling rates, and the same optical connector is used for both S/PDIF and ADAT data formats. Before recording, it's necessary to select a Program to record into, which may be done by depressing the Hold button, then using the Store key to step through the Program numbers. It is also important to manually set the sample rate of the D90 to match that of the source, and different Programs can be recorded at different sample rates if required. This information is stored as part of the Program.

The type of digital input is selected in the Setup menu, one of the three main display modes selected by means of the Disp Sel button. If the source is an ADAT, the ADAT tracks 1‑8 correspond with the D90's tracks 1‑8. One of the great advantages of the ADAT interface is not just that you can connect the machine to an ADAT, but that the D90 can also be integrated into a digital system where the mixer has an ADAT‑standard digital interface. If the source is S/PDIF, the left and right channels can each be routed to any of the eight D90 channels. The S/PDIF output can select any track pair for output.

To reset a channel for analogue input, it is only necessary to ensure that it isn't assigned to a digital source. Also in the Setup menu is the master/slave status of the machine for multiple‑machine operation, device ID number, sample frequency IDE/SCSI drive selection, and other basic options. Selecting a track for recording follows the usual rules of arming the track via separate Record buttons for each track, and putting the machine into input monitor mode for armed tracks is simply a matter of pressing Record twice.


Basic operation is very much like a tape‑based multitrack machine, but of course the 'rewind' is much faster. Most functions are straightforward, but I still feel that the procedure for storing in and out locator points for the auto‑punch‑in mode is unnecessarily‑long winded, involving, as it does, pressing the Store button first to grab the necessary time value, then pressing the Auto Punch In or Out key to assign it to the appropriate in or out locator memory. If the punch in and out points are very close together, this is simply too clumsy — a system requiring only a single button‑press for each point would have been rather more satisfactory.

The same is true of selecting start and end points for edit selections. But, this aside, you have everything you need — auto looping, adjustable pre‑roll, and a rehearsal mode to let you hear the effect of your punch‑in before you commit yourself. This all works extremely smoothly, and my only minor whinges are directed towards the occasionally cryptic display and the fact that the control buttons look too much alike. For example, Locate could usefully have been made a different colour or size to the other buttons. I'd also have liked record‑ready warning LEDs directly over the arming buttons, rather than only at the bottom of the level meters — which aren't aligned with the record buttons. However, the lack of multi‑function buttons is laudable — you have to depress two buttons at once to get to some functions, but that's about as complicated as it gets.

Though not exactly silent, the disk drive in the D90 is reasonably quiet, with only the faintest of clunkings and whirrings to betray its existence. Even so, you wouldn't want to have a sensitive mic right on top of it, which is why the remote front panel is such a good idea for solo recordists. Project studio owners will also appreciate the direct MTC output for sync'ing sequencers, something that ADATs still need outside help from a BRC or similar to achieve. Though low‑cost hardware does now allow MIDI sequencers to integrate audio with multiple outputs, the sound quality of systems with on‑card converters doesn't come close to what you can get out of the D90, especially when it comes to dynamic range and background noise. Though some cards have on‑paper figures that get close to the D90's 92dB, in a real‑life installation the figures are likely to be tens of dBs worse than this, and most cards we've tried so far have been hard pushed to produce better than a 60dB signal‑to‑noise ratio.

For all practical purposes, the recording quality is as good as DAT or ADAT, punching in and out is seamless, and the most commonly executed functions are reasonably straightforward. More advanced sync scenarios, such as running multiple machines or integrating with ADATs, requires a bit of careful manual reading, but the information is there if you look hard enough — it's just that it could have been presented a lot better than it is. If there's a downside to the actual operating system, it's that editing is really destructive, so you can't conserve disk space by re‑using the same section of a track again, as you can with a true playlist system, and aside from one level of undo, you can't get back to an earlier point in a project if things start to go horribly wrong. Even so, that's still one stage of undo that you don't get with a tape recorder, and even though you can do copy and paste editing between a couple of ADATs, it's much faster with the D90, and you only need one machine to do it.

Thanks to my friend Paul Joyner, I was able to verify that the D90 slaved OK directly to his Fostex RD8 ADAT machine, but the manual doesn't make it obvious that the slave machine needs to be set to Chase mode — otherwise MMC will start it playing, but it won't find the right position. It also proved straightforward to pass ADAT recordings to and from the D90 via the optical interface.


Price restructuring means that the D90 isn't much more expensive than the D80 originally was, yet it contains a number of genuinely useful enhancements, the most notable of which are the SCSI option, the removable drive, the ADAT interface, and more flexible sync options. I'm particularly enthusiastic about the inclusion of an ADAT interface, and it's also useful that D90s can sync in both master and slave modes. The flexibility available from combining multiple D90s or a mixture of D90s and ADATs in a synchronised system is extremely welcome, as it allows ADAT data to be lifted off, edited, and then replaced to tape relatively simply.

The basic principle of operation remains the same as for the D80, however, and I feel that, for a great number of users, this relatively simple approach is absolutely right, though both the display and the manual could be more friendly towards inexperienced users. The way in which the punch‑in and ‑out points are stored could also be improved, and the buttons could be better differentiated, but most operations are reasonably intuitive.

For 16‑track work, you could link two D90s, though I'd be tempted to hold out for the forthcoming 16‑track hard disk recorder from Fostex (the D160) if that's specifically what you need to do. However, if you need a stand‑alone 8‑track tapeless recorder that combines simplicity with flexibility and great sync facilities, and can be readily interfaced with an Alesis ADAT (providing you have a MIDI interface for your ADATs), there's really no contest at the price.


A D90 internal tempo map can contain up to 64 tempo changes, and, once the tempo map has been created, the D90 can send MTC (related to absolute time, with up to six hours offset) to sync a sequencer or other MIDI device. Alternatively, MIDI Clock (with Song Position Pointers) can be used to sync those systems not compatible with MTC, and the D90 fully supports MIDI Machine Control. To allow time for sync to occur, the D90 is set up so that ABS 0 occurs a couple of bars before the song start point, so that by the time the song start is reached, the external device should have had time to sync up.

MTC is also used when multiple D90s are required to run in sync, with the units being daisy‑chained via both their MIDI and optical data sockets. Engaging Chase Lock ensures that all the machines in a multi‑machine system are completely in sync during recording and playback, though if an error of greater than 10 frames is detected, the slaves will be muted and a re‑chase operation actioned until sync is restored. According to the manual, this doesn't normally happen, but as we only had one D90 for review, there was no means of testing the effectiveness of locking multiple machines, other than with an ADAT.

To sync to an ADAT, both MIDI and optical data connections are needed, which is why the Fostex RD8 provided a convenient way to test the system, though we also confirmed that users of conventional Alesis ADAT or ADAT XT machines can lock up via their BRC remote controls. Perhaps the inclusion of an Alesis‑style 9‑pin sync interface would have enabled D90s to behave as virtual ADATs in non‑BRC systems? It seems odd to have come so close without providing full ADAT emulation.

The D90 is perfectly able to slave to an external MIDI device capable of providing MTC, such as a sequencer. For this to work, the D90 must contain a recording, even if only of silence — if there's no recording, the machine can't sync. Once in sync, the real recorded parts can be added and the blank audio track or tracks overwritten. For MTC lock to be maintained, the source speed should be within plus or minus 5.6% of that of the D90. Outside these limits, chase lock sync cannot be maintained.


  • One‑box solution to hard disk multitrack.
  • Better sound quality than most soundcard‑based computer systems.
  • Useful range of features and interfacing facilities.
  • Generally easy to use.


  • The manual could be a lot shorter and a lot clearer.
  • The plasma display often displays cryptic characters


If you liked the D80, the D90 offers more features, more flexibility and more options for relatively little extra cost. It provides a very straightforward and cost‑effective way of getting into tapeless recording, and you generally won't have to worry about needing external sync boxes.