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Nomad SMC

MIDI-SMPTE Converter

As the price of SMPTE synchronising devices continues to fall, more and more home studios will be availed of their sophistication. Simon Trask checks out the latest breakthrough to find out it's not only cheap but British.


The two worlds of MIDI and SMPTE have been united for three years, but only now has the union been made accessible to the musician in the street - thanks to a new British company.


ALTHOUGH SMPTE TIMECODE was developed back in the late '60s to facilitate precision editing of video tape, its use has developed far beyond this initial brief to encompass the audio and video worlds - individually and together.

With the increasingly high profile of MIDI sequencing in the recording world, SMPTE timecode (or SMPTE/EBU timecode, to be exact) is now becoming the de facto standard for synchronising audio and MIDI, too. This requires a device that not only reads and writes SMPTE timecode, but also converts from SMPTE to MIDI.

Roland's SBX80 (reviewed in E&MM February '85) is one of the earliest examples of a SMPTE/MIDI converter, but since that time, an increasing number of such devices have been finding their way onto the market. And it's a trend which shows no sign of abating.

But until now, this facility has been outside the reach of many musicians, who have had to make do with the less satisfactory sync-to-tape methods such as FSK, which are quite capable of keeping everything in time, but provide no information on position in time. While these inferior methods simply record a constant timing reference onto tape, SMPTE timecode is a much more sophisticated concept altogether, in that each frame (remember timecode's video origins) has its own unique 80-byte digital code "word" which records hour, minute, second and frame-count values.

When transplanted into the purely audio domain, SMPTE's importance is that it provides an absolute timing and position reference which is accurate to 1/30th of a second (at the maximum frame rate of 30fps). MIDI's equivalent when it comes to defining sequence position is the Song Position Pointer, which is essentially a count of 16th notes (six MIDI clocks) elapsed since the start of a sequence. An SPP value of 128 would indicate that you were eight 4/4 bars into a sequence. MIDI's Song Position Pointer can store a value up to 16,383. Bearing in mind that these are 16th notes, this means that at a tempo of 120BPM, you can locate a MIDI position up to 34 minutes into a composition.

A SMPTE/MIDI converter has to do two things once a tape has been striped with timecode. When the tape is running, it has to translate received SMPTE code into MIDI clocks which are sent at a tempo rate that you select on the converter; when you shuttle the tape to a new position, it has to translate the SMPTE time at that position to a MIDI SPP value which will define an equivalent position in a MIDI sequencer. For instance, a SMPTE time of 00:02:00:00 would translate to a MIDI SPP of 960 for a 120BPM tempo. One word of advice: make sure your sequencer can actually respond to the Song Position Pointer code - if not, you can forget SMPTE.

Once the above-mentioned basic functions are in place, there are all manner of extra features which can be added to make a SMPTE/MIDI device more flexible in operation, and until now, manufacturers have gone for this approach in preference to a scaled-down, budget unit - sometimes at the expense of user-friendliness.

Format



NOMAD'S SMC1.0 (the initials stand for SMPTE MIDI Computer) has the distinction of being the first standalone SMPTE/MIDI converter to be made available for less than £500.

It's a compact, lightweight unit which you should have no trouble finding shelf space for. On the top panel is a helpful block diagram which illustrates in an uncomplicated fashion what the SMC gets up to. A sizeable LED window handles the unit's display requirements, while below this are nine buttons which take care of the SMC's operation.

The rear panel provides Tape In and Out jack sockets, MIDI In, MIDI Thru and two MIDI Outs. The MIDI In is particularly valuable, since performance data received at this port is merged internally with MIDI timing data before being sent via the MIDI Outs - a task which the SMC handles unflinchingly, even when presented with the most manic of MIDI performances. The significance of this is that you can record sequenced and taped parts together, or in any order you want - though in practice the true usefulness of this feature will depend on how your sequencer deals with recording and playback in external sync mode.

Nomad have provided the four standard SMPTE frame rates: 30, 30 drop-frame, 25 and 24 frames per second. Thirty fps is used for monochrome TV signals, thirty drop-frame is the American NTSC colour system for TV and video, and 24fps is the standard for film. Twenty-five fps is the EBU (European Broadcasting Union) TV and video standard, which adheres to the same 80-byte "word" format as SMPTE with a few small differences in coding.

For audio-only applications, it doesn't matter which frame rate you use - though Nomad recommend 25fps, which is the default rate on the SMC and (as mentioned above) the European rather than American standard.

Once you've connected the SMC's tape out to a track on your tape machine (ordinarily an outside track) and set a suitable recording level (somewhere between -3 and -7dB), start the tape and then press the Gen button on the SMC. This stripes the tape track with SMPTE code, beginning from zero time.

Next, rewind the tape and hit the SMC's Read button. When generating and reading timecode, the SMC's display shows time advancing, but for reasons of economy Nomad have only provided three digits - which means the display counts through 10 minutes (9:59) before wrapping round to zero again. Of course, this doesn't affect the timecode on tape, and for songwriting applications (which is really what the SMC is intended for) the limitation shouldn't be too much of a problem.

The manual states emphatically that noise reduction shouldn't be used on the timecode track, which could be bad news if you own a personal multitrack machine that doesn't allow NR to be switched out. But one such machine (the Tascam 244) which I used with the Nomad synced up perfectly first time and every time, which suggests Nomad's manual writers are erring on the side of caution. SMC chases the tape perfectly, and the sequencer (I tried both Pro24 and Iconix) locks to tape within 1-2 seconds. The SMC also tracks consistently through tape dropouts - so all in all, a very robust unit.



"The unit only allows you to set an initial tempo - you can't arrange for tempo changes to occur during the course of a song."


A "Bad Code" LED lights whenever the unit can't read timecode off tape properly - which, disconcertingly, includes occasions when it's reading no code at all.

Also disconcertingly, the SMC sends out a stream of MIDI Stop codes when it's reading nothing, which caused problems with both my sequencers when I wanted to record into them while they were in external sync mode. With Pro24 I was able to sidestep the problem (after a fashion), but not with the Iconix. Fortunately System Exclusive, Iconix' designers, have now ironed out the problem from their end.

After you've striped the tape with SMPTE code, you have to define both the sequencer start point and the tempo. The task of a SMPTE/MIDI converter is essentially to keep a MIDI sequencer in a steady relationship with the timecode (a bit like marriage guidance, really), which means that it must begin the sequencer at the same SMPTE time every time for each recording, and that it must bridge the gap between absolute time (SMPTE timecode, expressed as hours, minutes, seconds and frames) and relative time (sequencer tempo, expressed as beats per minute).

Nomad's unit fulfils both these requirements successfully, if in a rather unsophisticated fashion. In order to select your sequencer start point on the SMC, you have to hit the unit's Start button "on the fly" when playing back (reading) the SMPTE-striped tape. The SMC then stores the SMPTE time at which you hit the button internally, and from then on sends a MIDI Start code whenever this time is read.

Once you start laying down tape parts in sync with sequenced parts, it's crucial that the sequence start point remains unaltered - otherwise tape and sequencer will run in a constant relationship to one another, but will be out of step.

Pressing the SMC's Tempo button allows you to specify a tempo within a range of 30-255 BPM using the unit's +/- buttons. But a critical consideration for anyone thinking of buying the SMCI is that it only allows you to set a single, initial tempo - you can't arrange for tempo changes to occur during the course of a song. Bear in mind that even if your sequencer allows you to specify extensive tempo changes internally, they'll go to the wall when the sequencer is running off an external sync. This is because MIDI synchronisation also defines tempo, through the rate at which MIDI timing bytes are received referenced to the MIDI standard of 24 timing bytes per quarter-note.

Finally, the SMC has no battery backup, so start and tempo settings have to be saved to tape before you turn the unit off. There is, however, a Verify facility for inveterate paranoics (or perhaps just the sensibly cautious) among you. When you return to the session later on, the first thing you'll need to do is load the start and tempo settings back in. Laborious, but under the circumstances, essential.

Verdict



ONE THING IS clear. If you're looking for full-blown SMPTE/MIDI sophistication, you'll need to look to such devices as Steinberg's SMP24, the Bokse SM9, the Fostex 4050, Real Time Logic's Event or Yamaha's new MSS1. Sadly, that also means looking at a price tag of between £800 and £1000.

Nomad's SMC, on the other hand, may be short on sophistication, but its strength lies in its very simplicity (it's incredibly easy to use) as well as in its budget price. The unit is ideal for musicians and budget studio owners who are looking to upgrade from sync-to-tape to SMPTE, but can't afford the sort of financial outlay this has previously entailed.

But Nomad aren't having it all their own way, as Bokse are about to bring out the SM1 SMPTE/MIDI converter, which retails for £449; that's just over £100 more than the SMC1, but then it does add 16 tempo changes, an offset facility, a full time display, six MIDI Outs (really), and optional battery backup.

With the possible exception of the SMC's single tempo setting, the compromises that have been made in the name of cost-cutting shouldn't cause you any lost sleep - just remember to save that start point.

What really matters is that the SMC allows your sequencer and tape recorder to be locked together wherever you shuttle the tape, and that sequencing and tape recording methods suddenly become interactive.

In short, Nomad are to be congratulated for making SMPTE both affordable and accessible to musicians.

Price £344 including VAT

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Music Technology - Copyright: Music Maker Publications (UK), Future Publishing.

 

Music Technology - Aug 1987

Gear in this article:

Synchroniser > Nomad > SMC 1.0

Review by Simon Trask

Previous article in this issue:

> Box! Clever

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