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Tascam DA88 | |
8-Track Digital Tape RecorderArticle from Recording Musician, March 1993 |
Tascam's digital 8-track recorder is designed to meet the needs of professionals, yet is costed to appeal to the home studio market.
Tascam's DA88 would appear to be a direct threat to the current monopoly enjoyed by the Alesis ADAT. But is the market really large enough to sustain two incompatible 8-track digital formats? Dave Lockwood checks out the challenger.
Housed in a 4U rack chassis, the DA88 weighs in at a substantial 14kg, the extra weight presumably being in the chassis construction. From the back, the major system components can all be seen to be on individual, horizontally-mounted plug-in boards; the input interfacing and A/D conversion; the output interfacing and D/A conversion; the SY88 timecode/sync board (in fact a blanking panel on the review model, the SY88 not being available in time); the DSP board housing digital signal I/O and connection for the optional 24-channel remote meter unit (MU8824); finally, the System board, handling remote/sync operations.
The DA88 is force-cooled by a constantly-running 4-inch fan, venting to the side which, although quiet, is still audible when you're working close to the machine; multiple transports would certainly compound this. Using the unit with the remote, so that it can be distanced somewhat, or rackmounting it, reduces the noise to insignificant proportions.
Audio interfacing at both +4dBm and -10dBV is available, the former also being provided on an electronically balanced 25-pin D-sub. The standard low-level, unbalanced convention is observed, with phonos being used, ensuring compatibility with existing semi-pro multitrack looms.
The DA88 transport controls will be immediately familiar to existing Tascam multitrack users and incorporate most of the features evident on their present analogue models. The main difference here is that the locate functions and auto drop-in/out are frame-accurate, and no longer subject to possible drift due to tape slippage. The main transport controls are large, long-travel affairs, each with an adjacent status LED.
On the basic machine (without the remote) only two locate points are available, entered simply by pressing Memory 1 or 2, either on the fly, or with the tape stationary at the appropriate place. The remote extends the number of memories to a rather more useful 99. Memory points can then be located instantly just by pressing Locate 1 or 2. Activating Repeat will cycle between them. The status of the Auto-play switch determines whether Stop or Play will follow a locate function.
Auto drop-in works in the same way as on Tascam's analogue machines, by entering Rehearsal mode and then performing the drop-in on a dummy run to set up the In and Out points. Pre and post-roll default to sensible figures, and the machine really does everything for you from that point. You can rehearse the drop-in as many times as you need to before activating Auto In/Out to actually execute it. The procedure can be repeated, if necessary, on the same in and out points just by reactivating Auto In/Out.
What is monitored from the tape outputs of the machine is determined by selecting either All Input, Auto Input, or Insert. All Input is obviously self-explanatory; while in Insert, monitoring carries the track output until it enters Record, when it switches over to Input. Auto Input provides Input monitoring during stop or fast wind.
Tracks are selected to Record Ready via a switch beneath the appropriate LED column meter. These are clearly marked with track numbers, and there is a status LED above each one which flashes to indicate Ready mode, remaining constantly illuminated during Record.
Level metering is via high-visibility, peak-reading, 15-segment, yellow LED bargraph, with a single red element at the top indicating Overload. As always with digital systems, the onset of clipping is sudden and very audible, and therefore must be avoided. The DA88 clips like any other digital system — it sounds very nasty indeed.
The DA88's main display (8-digit, red LED, 7-segment format) normally shows Absolute tape time in Hours, Minutes, Seconds and Frames, derived from the tape format information. It can be cycled through other options, however, to display either of the memory points, or the Varispeed figure, drop-in crossfade time, machine offset, track delay, or pre-roll time. Increment/decrement switches, with intelligent scrolling, can be used to change values. Record Inhibit, Error, and Warning LEDS are also incorporated, the latter normally being accompanied by an explanatory message in the main display.
Inserting a formatted tape into the machine, or rewinding one to its beginning, is acknowledged by the display 'bot', confirming that this is the start of the tape.
DA88 systems consisting of multiple transports can be operated without the optional timecode board (just as ADATs can be chained without the BRC). The proprietary timing information recorded as part of the sub-code can simply be fed from the master to the slaves. Lock-up is said to be in the order of 1-2 seconds per machine in the system. The worst case figure arises from, say, going from Fast Wind straight into Play, while the best figure relates to going into Play from Stop, where the transports will already be parked within a few frames of one another. I am assured that a two-machine system can be Play-locked from Stop in under 1 second, while a 3-machine stack, being asked to Play straight from a lengthy rewind will still be up and running in under 4 seconds, though with only one machine in the UK at the time of writing, I couldn't verify this.
It is only when SMPTE/EBU is required for external synchronisation that the SY88 card comes into play. Incoming timecode is converted to sub-code data for recording, being re-synthesized on replay. As far as the user is concerned, however, timecode goes in, and timecode comes out, so everything looks normal, but the output code is always a regenerated signal, which should therefore prove to be clean and stable.
For use with conventional MIDI-to-Tape FSK sync units, a tape track must be used to record the time code in the same way as it is with analogue machines.
Two remote control units are available; the RC848 multi-unit remote, and the simple RC808 single-unit remote which replicates the front-panel transport functions, record switching, 2-point autolocate, monitor switching and auto drop-in controls available from the DA88.
Connecting to the Sync In of the master transport, the large remote has substantial, positive transport controls, and replicates the DA88's Shuttle facility, with the further enhancement of a jog wheel. The number of autolocate memories is expanded to 99, with dedicated Record switching for up to 48 tracks (six DA88s), in addition to centralised transport control. Two large LED time displays, in Hours, Minutes, Seconds and Frames, allow tape time and locate times to be displayed simultaneously, which always makes session 'memory-management' that bit easier. A succession of cue points can be picked up on the fly, storing automatically into sequential locations; numbers can be entered directly into memory via the numeric keypad, and cues recalled for examination or editing at any time.
Operation of the more sophisticated functions is made considerably easier by the inclusion of an LCD display. Here, factors such as varispeed amount, sampling frequency, crossfade times for drop-ins, machine offsets, and so on, can be set up. A simple menu system, and dedicated data increment and decrement switches make operation reasonably straightforward.
The RC848 remote duplicates the DA88's shuttle facility, and adds an additional jog wheel function. Shuttle allows the tape to be replayed at a speed determined by the position of the control, ranging from a quarter to eight-times normal playback speed. Rotating the control clockwise from the detented centre position gives forward playback, whilst turning it anti-clockwise initiates reverse playback. The further you turn, the faster the playback.
Reconstructing digital audio at drastically altered speeds, however, is a complex task, and the audio output is always considerably degraded. The further you deviate from normal speed, the more 'crunch' you get. Entering Jog/Shuttle mode automatically attenuates the output by a few dB to avoid any risk of feeding high level distortion into your monitors.
At very slow speeds audio break-up is considerable, occasionally muting completely while still appearing to be above the minimum operational speed. But I did find that after a while I seemed to learn the characteristics of the controller and was able to locate with some accuracy.
Shuttle is not fitted to this machine on a whim; the Shuttle control as implemented emulates its video equivalent, ensuring that both DA88 and RC848 will fit comfortably into any audio-for-picture environment. A DA88 transport in Shuttle mode is designed to be able to keep up with video transports driven by a video edit controller.
The jog wheel on the remote functions in a related fashion. The inner ring of the concentric Jog/Shuttle controller has a pair of finger-detents. Inserting a digit, one can simply rotate the wheel to achieve playback at the desired speed. The gearing was a little adrift on the review model, requiring excessive effort to achieve a reasonable playback speed, but I'm told the software has already been updated to correct this.
Before a recording can be made using a new tape, it must be formatted, though it is not necessary to pre-format the entire tape before use. Incomplete formatting can be picked up and continued from where it ends, and even discontinuous formatting is permitted. The DA88 simply rolls on until it finds the next bit of valid tape. However, you can't re-format a tape that has previously been used for video recording. Before formatting can commence, you have to make a choice between the two sample rates on offer; 44.1 and 48kHz. If you are originating material that may end up on CD, it is probably worth recording it at 44.1 kHz — unless you have a good reason for using 48Khz.
Audio can be recorded at the same time as formatting, so timecode can be striped in the same pass (into sub-code if you have the SY88 board), or onto an audio track.
Once you've got a formatted tape in the machine, and selected between analogue and digital inputs (defaults to analogue), you can treat the DA88 much like any other multitrack recorder. Pressing Record and Play simultaneously gets you into Record, but dropping-in on the fly can be performed using just the Record switch. Manual dropping-out is via the Play switch so the control format follows that established on Tascam's analogue machines.
To the engineer, the 'feel' of a recorder's transport is perhaps the most important consideration apart from sound quality. Operators with years of experience on analogue transports tend to find rotary-head systems (DAT, or anything based on a video transport), rather clumsy in comparison; a complex and lengthy tape path limits the practical speed at which safe fast-winding is possible. The higher speeds needed for rapid relocation can only be achieved by disengaging from the rotary head mechanism. Domestic videos give you a choice of slow 'picture-search' wind, or conventional fast wind, entered via Stop; DAT, similarly has audio-search, whilst ADAT offers slow wind, accessable straight from Play, or fast wind available only via Stop. The unlacing process, however, takes time.
The DA88 behaves far more like a conventional transport; when you hit fast wind from Play, the response is instant, and the speed also ramps to a maximum of 100 times play speed after a while, allowing fine control over a short relocate, whilst minimising the tedium of a long run (the DA88 can, in fact, wind the whole length of a 113-minute formatted tape in just 80 seconds). With a slow linear tape speed, combined with a fast, intelligent transport, the DA88 can be remarkably quick to find its locate points. Start-up is always clean and consistent.
Observing the DA88 transport at work with the cover removed for a brief period reveals that the 226-degree tape-wrap remains the same in all modes other than Stop, which retracts the two main guides. Audible location to precise points is taken care of via the Shuttle facility which stops the tape, but maintains head motion and tape contact — in effect, a Pause mode. Turning the centre-detented Shuttle control to either side then commences speed-governed replay, forwards or backwards according to which direction you rotate. The range is from one quarter to up to eight times normal play speed. Shuttle mode ceases automatically, defaulting to Stop if the machine has not been used for 10 seconds.
The Track Delay facility allows a musical part to be 'slid' backwards (or forwards, by delaying all the other tracks) in time, thereby adjusting its musical 'feel'. A maximum delay of 150ms is possible, adjustable in the finest possible increment of single-sample steps.
Not all 16-bit linear digital audio systems sound the same. The type of converters used, the filtering they necessitate, the coding method, the error-correction strategy, and many other factors involved in simply making the system work, all have their say in what we eventually hear. Major improvements have been made in digital audio over the last decade, mainly as a result of users being willing to say 'I don't care how theoretically perfect it is, it still doesn't sound right'. Tascam's pedigree in the digital audio world is well established via their DASH format digital multitrack, and their respected DA30 DAT recorder, and obviously the DA88 benefits from that experience. What much of the industry is agreed on is that a whole group of recorders with certain characteristics — 64 times oversampling, delta/sigma converters, shallow-slope filters and so forth, impart something audibly desirable to their signals. The DA88 conforms to that profile and sounds as good as any 16-bit digital system I have ever used.
Drop-ins, be they programmed, manual, or via footswitch, are aurally impeccable. With the new signal being digitally crossfaded with the previous one, clicks and other waveform discontinuities are a thing of the past. Crossfade time defaults to 10mS — fast enough to appear instant, yet long enough to smooth out the transition — and can be increased in 10mS increments to a maximum of 90mS.
A drop-in on a multitrack digital audio recorder is actually quite an engineering feat, necessitating the reading of existing data into a RAM buffer, before crossfading it with the new data, and then writing the new information back to the storage medium. Because this process involves an element of re-recording existing information, it has been suggested that some digital multitrack systems will be prone to error when repeatedly dropping-in on the same spot, am not sure how many repetitions are supposed to be required, but I did as many as I could stand listening to without generating a hint of a problem. In real work, I don't think I would ever actually allow this to occur, but it was interesting to see the DA88 pass the test.
Digital dubbing on the DA88 is not limited to merely copying signals from one machine to another. Simply by cross-patching the 25-way D-sub digital I/O it would seem to be possible to achieve internal track-bouncing in the digital domain. The TDIF-1 format handles tracks in pairs, and therefore limits you to bouncing even-numbered tracks to even-numbered tracks, and odd to odd, but you don't have to bounce both tracks of the pair — if you only put one of the destination pair into record, you will only bounce its matching odd/even source track. It would certainly be worthwhile making up a digital patchbay if you could foresee yourself making any significant use of this excellent facility.
With Fostex committed now to ADAT, does Tascam's DA88 herald the start of yet another format war? Despite the differences in primary market orientation, I think inevitably it must — with investment in R&D running to millions, there is so much at stake. There is no doubt that, in some fields, the format able to show an early lead will pick up additional sales simply through being perceived as the de facto 'standard'. If most people have 'format X' you won't be able to simply take your 'format Y' tapes to your friends' studios, or into a similarly equipped commercial facility. Ultimately, however, you can't beat the market; the professional user in particular will always buy the product that comes closest to fitting the profile of his requirements. There can be no doubt that Tascam have targeted audio post-pro with the DA88, but in so doing, they have lost nothing in the music market — no-one is exactly going to complain that their recorder is over-built!
The 'DA88 system', as a whole, seems well-conceived, with a sophisticated remote for those who need one, but with the option of a separate sync board for those who just require time-code or to interface with a video edit controller.
In the long-term, a number of issues remain unaddressed. No-one really knows at this stage what the data-life/reliability of either format will be. If I had to guess, I would say that the chances are that each of them is equally technically viable — they are both elegant engineering solutions to the same problem. Projected head-life for the DA88 was unspecified at the time of writing, but a company source was willing to project 'longer than analogue' and a head-replacement cost 'cheaper than analogue'. The cumulative head-drum rotation time is actually monitored by the system, the figure being available on interrogation via the software.
Another good solid pro feature is error-rate monitoring. No manufacturer is particularly keen to display how hard their error-correction is having to work in 'normal' operation, but interpolation-rate monitoring remains the best guide to detecting a potential problem before it occurs. The DA88 Error LED illuminates only when an 'uncorrectable' error has occured and the interpolation strategy has therefore been implemented (this didn't occur during the review period). An 'uncorrectable' error does not mean an audible 'glitch' in the output, merely that the coding strategy has not been able to be certain that it has reconstructed the exact bit-status and has therefore made an intelligent guess — all digital systems do it, but only some are prepared to make this information available to the user. In a multi-machine digital system, a tape showing an increasing error-rate can be cloned before giving audible problems. Most professional users will probably implement a regime of automatic renewal of heavily worked tapes anyway, but it is helpful to have a bit of guidance in optimising usage.
Routine maintenance appears to amount to precisely zero; there is nothing to check, nothing to align — inveterate machine-tweakers will hardly know what to do with themselves.
Much will rest on the lock-up performance of synchronised transports. With only one chassis I was obviously unable to verify this, but if it is as fast as claimed, then it will be operationally very good indeed. If the future is to lie with multiple-chassis multitracks, then they must approach the capability of responding as if they were a single transport, whilst retaining all the advantages of a split system.
Whatever your preconceptions in the ADAT versus DA88 arena, the DA88 is undeniably one of those products that inspires a high degree of appreciation of its engineering. The fact that Tascam, with all the tape options available to them, chose to follow the 'high-density' route previously taken by both Akai and Yamaha may also be seen as significant in terms of format confidence. Whichever way you look at it, this is a very serious machine both for professional audio and AV applications, or for high quality home recording.
Further Information
Tascam DA88 £3,999; RC848 System Remote £999; RC808 Simple Remote £129; SY88 Sync board £499; IF 88AE AES/EBU Digital Interface £799; SDiF-2 Digital Interface £925; MU8824 24-channel Meter Bridge £599. Prices include VAT.
Tascam UK Ltd, (Contact Details).
Heads: | Rotary, 4-head. |
Tape: | Hi-8 (metal). |
Tracks: | 8 (plus timecode in subcode with SY88). |
Tape Speed: | 16mm/s. |
Recording time: | 113 mins (at 48kHz) with PAL 90 tape. |
FF/Rewind: | 80 sec for PAL 90 tape (100 x speed). |
Audio scan (Shuttle/Jog): | one quarter to nine times speed. |
T/C scan | 100 x speed. |
Wow and flutter: | Unmeasurable. |
Sampling frequency: | 44.1/48kHz switchable. |
Quantisation: | A/D 16-bit linear/64 x delta-sigma; D/A 18-bit linear/8 x oversampling. |
Varispeed: | +/-6% (41.45 to 50.88kHz in 0.1% steps). |
Frequency response: | (+/-0.5dB) 20Hz to 20kHz. |
Dynamic range: | Better than 92dB. |
Distortion: | Less than 0.007% THD. |
Chan, separation (1 kHz): | Better than 90dB. |
Digital crossfade: | 10mS to 90ms (variable in 10mS steps). |
Track delay: | Max 150mS (variable in individual sample steps). |
Analog I/O: | D-sub, 25-pin (+4dBm, balanced); RCA (phono) x 8 (-10dBV, unbalanced). |
Digital I/O: | D-sub, 15-pin (TDIF-1 format). |
Dimensions: | (WxHxD) 482mm x 197mm x 377mm. |
Weight: | 14kg. |
Tascam DA-88 - Digital Multitracker
(MT Mar 93)
Tascam DA88 - Digital 8-Track Recorder
(SOS Apr 93)
Browse category: Digital Tape Deck (Multitrack) > Tascam
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Review by Dave Lockwood
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