MIDI > Thru Boxes, Mergers, Patchbays & Sync Boxes

Bokse SM-9 (1987)

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chrisNova777:
http://www.muzines.co.uk/articles/bokse-sm-9/1360



--- Quote ---The increasing popularity of SMPTE has meant a corresponding growth in sync units. We take a look at this one from Bokse.


SMPTE is gradually taking hold as the system for synchronising recording and sequencing gear to tape. This month we take a look at a unit specifically designed for use with SMPTE.


It's nothing new to find a unit which embraces SMPTE, EBU and MIDI. After all, Roland released one some time ago: the SBX-80 (reviewed in H&SR March 85), which enabled the user to record a SMPTE time code onto tape, retrieve it and convert it to MIDI timing data, and to run drum machines and sequencer systems from it with great accuracy. When it first came on the market at just under £1000, a SMPTE-based system at that price was unheard of, but as you know, the fickle finger of time does the most extraordinary things to the world of musical technology, especially its price.

To date we have had the Fostex 4050 Autolocator at £899 which offers tape machine transport and SMPTE to MIDI control in one unit, and now we have the subject of this review - the Bokse SM-9 - weighing in at £829 including VAT and packing one hell of a punch to boot despite its cheaper retail price. The Bokse has the ability to read and generate SMPTE/EBU code simultaneously, can store up to 128 cue points and will output event points as MIDI and +5V triggers. Definitely a match for its competitors.

Grappling with the Concepts


For those of you who don't already know (those of you who do can smugly read on to the next bit), SMPTE was introduced by the Society of Motion Picture and Television Engineers, hence the acronym. Its original intention was to synchronise film to a soundtrack, but it has great potential in audio studios too. Now widely used for video as well as film, SMPTE code carries digital information that accurately defines any given position on the recording tape in units of both elapsed time and video frames and so is altogether more comprehensive and flexible than an ordinary sync code from, for example, a drum machine. This added sophistication means that the track does not have to be run from the top in order to achieve synchronisation: once the machine sees the appropriate piece of code on tape, it locks onto it automatically. Users of MIDI sequencers and drum machines with simple sync to tape facilities will immediately see the implications of this feature in practical terms. A unit like the SM-9 which reads and generates SMPTE will allow you to drop in sequencer, drum machine, triggered arpeggio or sampled parts without having to take it from the top every time.

The frame rate for standard film use is 24 frames per second (fps), but through its application to the TV and video worlds, three more standards have evolved and the SM-9 can cope quite happily with them all. When powered up the unit defaults to 25 frames per second, because this is the rate used in Britain (derived from the 50 cycles mains frequency), and the British television standard, often called the EBU (European Broadcasting Union) code. What this means in application is an accuracy of 1/25th of a second (40mS) for any musical event. The American video standard is 30fps to cope with the American NTSC (jokingly referred to as the Never The Same Colour) television picture system. But before you start getting worried about all this technology let me tell you that this sort of sophistication enables the system to calculate the exact position of any 16th, 8th, or quarter note, and so the timing data can be related to musical note length.

Time Out


Now the preliminaries are dealt with we can take a look at the unit itself. Unlike the 4050 and the SBX-80, the SM-9 is rackmounting which will appeal to people who think free-standing units take up too much space, and annoy those who feel that having it with the control panel vertical in a rack will make it hard to manually tap in cue points. For the latter, a little extra cash will purchase the remote which has all the features of the main front panel without the MIDI and jack sockets. In essence, the operation of the SM-9 can be broken down into two parts: SMPTE Generate/Read and Events Control. To stripe the tape with SMPTE (record the timecode), and retrieve it, two jack sockets are provided on the rear panel. It's probably worth noting at this point that as the MIDI In and Thru, +5V outputs, and SMPTE Thru sockets are all mounted on the rear panel, a patchbay will probably be needed if the unit is rack mounted. Most engineers suggest that you use an edge track for striping and leave a spare track between it and the rest of the tape because it reduces the amount of crosstalk from the code to the other tracks and stops transient sounds like drums from interfering with the code itself. This is all well and good for 24-track operation upwards, but can prove awkward for Fostex B16 and A8 owners where the track spacing is limited by the width of the tape and outside tracks are all too easily damaged by mishandling and poor storage, and are prone to dropout. In practice, however, it's possible to record the code produced by the Bokse SM-9 a couple of tracks away from the edge. This is because the SMPTE sent to the tape has had its fast leading edges rounded off which helps to minimise the crosstalk caused by the high frequency content of its fast edged square wave signals. Care should be taken, though, to keep transient sounds away from the adjacent tracks. Once the code is on tape you simply switch the SM-9 to Read, run the tape from any position and the unit will decode the signal and display the time. I was pleased to find that although the manual suggests a recording level of -3 to -7dB for the code, on the knackered old piece of tape I used the Bokse unflinchingly decoded the signal in Read mode when drop-out caused the level to drop to -20dB and sharply recover to -7dB! Very impressive. What's more, as the unit can Read and Generate SMPTE at the same time, if your code has been well and truly corrupted at some point, a repair can be affected by reading up to the point of damage and then recording the new code over that section.

The Read mode will cope with fluctuations up to ±30%, allowing transports to be used in varispeed mode with no problem. This means that if recording a troublesome acoustic instrument that needs to be varisped, it's possible to use the code at the same time. However, I can't honestly think of many occasions on which this would be necessary. Far more likely uses are for things like altering the pitch of triggered sounds which have to be synchronised to tape. A sampled snare drum, for instance, could be too low in pitch for the Stuart Copeland sound you originally envisaged, but by recording it with the varispeed pitched down and consequently playing it back at the right pitch the desired effect could be recreated. Of course there are other ways of doing this, but it's nice to know that the Bokse is versatile enough to allow it.

The SM-9 can also be used in a 'stand alone' situation to run through and check sequencer or drum machine parts without going through the hassle of running the tape or de-syncing them from the Bokse. Simply pressing Generate followed by Read will cause the SM-9 to read its own internal timecode and permit as many dry runs as you need.


"...Bokse have increased the versatility of the SM-9 by allowing them to provide a 'gated' start! stop of any incoming clock pulses within the DC to 1MHz frequency range."


The Main Event


Event programming is split into four sections called Cue A, B, C, and D and each cue is capable of storing up to 32 different event start and stop points. This gives you a degree of control over drum machines and sequencers unparalleled at this price, but in order for the SM-9 to output MIDI timing data or clock pulses with reference to the SMPTE code, it needs to be told where to start from. This Tempo Start Time is then used as a reference point from which all the cues are taken and it can be set to whatever time is required in hours, mins, secs and frames. There's even an offset of 80 subdivisions for each frame giving a lining up accuracy of + or -0.5mS, which should satisfy even the most critical user. Programming on the SM-9 is easy; simply select the parameter you want to edit, and the relevant information comes up on the display, whereupon you may alter it with incremental controls and implement the command by pressing Enter.

The next thing you're probably going to want to do is define a Tempo for the composition. This is one of the areas where SMPTE scores over tempo-related sync codes because once the tape is striped any tempo can be used. Users of simpler synchronisation codes will know how limiting it is to be stuck with one tempo for a whole song and each song must have a new code. With SMPTE the practice is to stripe the tape from start to end and then program your alterations in tempo. 64 changes in tempo may be memorised and each tempo may last a maximum of 9999 quarter notes. For example, if putting music to a piece of video footage, you may need four bars at 150bpm for a piece of fast action then eight at 90bpm when things calm down. So you'd program tempo speed and duration in quarter notes (4 bars = 16 beats) into tempo memory one, step up to memory two and program in 90bpm for 32 beats. If you are keen to work it out in frames, the readout can be changed to frames per beat and a little simple mental arithmetic will ascertain how long you want a certain tempo to last. Obviously the faster the tempo, the fewer frames per beat.

Another limitation of the one-tempo synchronisation code involves the fractional but frustratingly audible delay when equipment with different response times is being run off the code. Compensation for this usually involves messing around with digital delays to delay the code and is a time-consuming process in which the different attack times of synthesiser patches can also become painfully irritating. Well, you can kiss goodbye to a lot of the hassle when you use the SM-9's Tempo Start Offset capabilities! This Offset control actually moves the start time within the time period of one frame and will consequently alter the position of all cues relative to the SMPTE. This means they'll be precisely in registration with any other equipment. Offset also has a range of values from 0-79 with each step offsetting or delaying the Tempo Start by 0.5mS, thereby giving a maximum offset of 80 steps x0.5mS = 40mS maximum (1 frame period at 25fps).

Imagine a situation where a bass sequence is run from a sequencer with a slower response time than the drum machine. To get the track to sound perfectly tight and punchy you have two options, either delay the cue to the drum machine or advance the cue to the sequencer. If the recording is not too far advanced, then it may be easier to delay the drum machine by experimenting with the Offset (2 steps = a delay of 1 mS) until it sits right on top of the bass line. Alternatively, if other instruments have already been recorded which sound tight with the drums, you would probably decide to advance the cue to the sequencer by moving the start time one frame earlier and creating a pre-delay effect where the higher the value of offset, the less the pre-delay. Another example of the usefulness of such a predelay involves the triggering of sampled sounds. A lot of sampling delay lines still have quite audible delay times before the sample triggers, but an advanced Tempo Start would take care of all that, running the drum machine or sequencer providing the trigger a little early to the beat to compensate. I'm sure you'll agree that the SM-9 would be a boon to any studio for this capacity alone and taken another stage further, you can have all sorts of fun delaying and pre-delaying music for realtime ADT and other delay effects.

Join the Cue


While you may use the incremental controls to program where you wish MIDI timing data to start and stop, there's an optional manual method of execution. A variable correction factor of quarter, eighth, 16th note, and even second/frame editing is available in this mode, thank goodness! You merely press the Cue button as near as possible to the right place, check and edit as necessary. Cue A can be set to output MIDI Start, Stop or Continue information, but you can also use it to activate older analogue systems that trigger off contact closures or require a +5V kick. The practical applications of the Cue system are in dropping in and out parts. A high-energy polyphonic sequence for each chorus could be given start/stop cues instead of the fuss of having to program the whole song into a sequencer gaps and all. Or even simpler, you may want to do a Phil Collins on the song and have the drums thundering in at the end of the track. A simple cue point start command for this could be set up in seconds.


"The SM-9 overcomes all the problems associated with the tempo-related sync code because once the code is down the user can choose the tempo required, and you don't have to start from the beginning every time something has to be dropped in."


Cue B and C each have 32 programmable cue points but are not used for MIDI control. Instead Bokse have increased the versatility of the SM-9 by allowing them to provide a 'gated' start/stop of any incoming clock pulses within the DC to 1MHz frequency range. In layman's terms this means that the user can feed in a clock pulse rate from another source to the Cue B or C front panel input and back out to control a non-MIDI sequencer or drum machine. A cue start point has to be programmed which opens the gate and lets the clock pulses through until a cue stop point at a suitable place in the composition shuts it all down. A neat way of allowing units to be stopped and started in sync with the timecode off tape.

Cue D brings us back to MIDI control, because not only does it have the familiar 32 cue points available, but also these can be tailored to output MIDI programme change data. For each cue, the user can set the time you want it to occur, the MIDI programme number (0-127), and finally the MIDI Channel (1 - 16). The lack of such control is one of he SBX-80's biggest drawbacks because its inclusion allows extensive MIDI-controlled mixdown capabilities. A change in delay programme here, movement from a a short to long reverb at another part of the song, not to mention programme changing keyboards being run on the mix. The potential is enormous.

It's a Knockout


Well, as you can see, I was favourably impressed with this unit. Its versatility with both MIDI and non-MIDI equipment is only further augmented by the other units in the Bokse range such as the Universal Synchroniser US-8 which solves incompatible trigger and sync code problems, the MH-2 MIDI Humaniser and the TS-4 Active Timebase. As it stands though, the SM-9 is not equipped to synchronise two or more machines such as tape recorders; that's not what it was designed to do.

The SM-9 overcomes all the problems associated with the tempo-related sync code because once the code is down the user can choose the tempo required, and you don't have to start from the beginning every time something has to be dropped in. The offset facility also negates the problem of triggering equipment with different response times by allowing the user to place the start command point a specified time earlier in the track. Real time delay and pre-delay effects can also be effectively controlled in this way. And the inclusion of the MIDI program change section places the Bokse SM-9 firmly ahead of the competition when it comes to creative mixdown capabilities. If you use timecodes and MIDI gear a lot, once you've tried this unit you'll wonder how you ever did without it! A winner.

The Bokse SM-9 costs £829 including VAT.
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