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Poor Person's SMPTE

J.L. Cooper PPS-1

Looking for an alternative means of syncing MIDI instruments to tape? David Mellor tries out a low-cost solution from J.L. Cooper Electronics - the PPS-1.


David Mellor volunteers to be Sound On Sound's captive poor person and checks out the pennywise alternative to SMPTE timecode from J.L. Cooper Electronics. Does cutting the cost mean cutting the performance or has the great god of synchronisation met its match?


Before MIDI was invented, long ago in the dim and distant past, there was timecode - or SMPTE as it is colloquially known. Timecode was strictly for the pros. They used it to sync up their audio and video recorders to each other, and because it was so useful, they didn't mind paying thousands of pounds for a SMPTE unit. Musicians were not aware of all this because they were still struggling along, trying to record in the good old-fashioned manual way.

Then along came drum machines in the shape of the famous Linn. This had a little jack socket on the back labelled 'Tape Sync', or words to that effect. Quite what you might want to sync up to in those days was a debatable point but, eventually, some bright spark took the bold step of leaving the drums off the multitrack and mixing them live from the machine - synchronised to the tape.

With the benefits, along came the snags. It was nice to have clean sounding drums that had not gone through the magnetic mangle, but the tape sync feature only worked if you started from the top of the track. Start half-way through the tape and the machine didn't have a clue where it was. Since these dark days, the good old tape sync socket has changed little. OK, so it runs MIDI sequencers now, but you still have to go from the top every time.

SMPTE timecode is in a rather better position because manufacturers have seen it as 'the way to go', not only because you can sync sequencers up to tape so that they always know where they are, but also because they can sell lots of extra boxes with jumbo price tags to the consumer - boxes which don't actually make any music. SMPTE is more clever than tape sync because it knows where it is on the tape all the way through the track. If you use SMPTE for synchronisation, you can start the tape wherever you like and be in sync.

Let's backtrack a little and look at conventional tape sync and timecode in more detail.

TAPE SYNC



Tape sync, in its very crudest form, is just a tone generated by the sequencer or drum machine, which you record on one track of the multitrack tape. The normal procedure is to record a few tracks so that you have the basic song structure sorted out, then play back the song and record the sync tone on the tape. The tone will subsequently tell the sequencer when to start and what the tempo is, including any changes that you programmed. The frequency of this tone bears a set relationship to the internal clock pulses of the machine, so if you replay the tape and set the sequencer to 'external sync', it will lock up to this tone and play in synchronisation with the music you have recorded on tape.

A more complex version uses a technique known as frequency shift keying or FSK. This procedure uses two alternating tones of different frequency, the rate of alternation setting the tempo of the track. The single tone technique is pretty useless because it is very delicate: any crosstalk from nearby tracks on the tape will be interpreted as extra clock pulses and, thus, sync will be lost. You can guess how annoying this is!

FSK is much better, although the choice of the frequencies of the tones has a good deal of bearing on the robustness of the synchronisation. For example, I started off synchronising with a Yamaha QX7 sequencer and a YMC10 MIDI tape sync box - which is now doing duty as the world's most expensive two-way MIDI splitter! I found it difficult to find a compromise on a level which was high enough to be proof against crosstalk from the adjacent track, yet low enough not to be a cause of crosstalk itself. I gave up and left a track blank between the music tracks and the sync track. When you only have eight tracks to begin with, this is a hard sacrifice to make.

The Yamaha QX5 (which doesn't need a separate sync box) was a great improvement because the frequencies of the FSK tones had been chosen with more care and I found that I could use track seven (the blank 'guard' track) for music without difficulty. Of course, I still had the problem of having to start from the beginning of the track every time.

Frequency shift keying can convey as much information as you ask it to, subject to the limitations of the medium, but so far manufacturers have only used it for timing information - it contains no data about the position of the tape or how far into the track you may be. It tells the drum machine or sequencer when to start and how fast to go - that's all.

TIMECODE



As I said earlier, timecode used to be strictly for the pros, and rich ones at that! When Roland brought out their SBX80 Sync Box at under £1000, it opened the door for other SMPTE-MIDI timecode units at affordable prices. The current holder of the most affordable SMPTE box title (that I know of) is the Nomad SMC 1.0 which I reviewed in the May '87 issue of Sound On Sound. Does £343.85 sound like too much to pay? In comparison with the prices we have been used to, it's a steal.

When you have had a taste of using timecode, there's no going back to the old ways of conventional FSK tape sync. Timecode, whether SMPTE or EBU, is a data stream recorded on tape which conveys information about timing in terms of hours, minutes, seconds, and 25ths of a second. When you take out a new reel of tape, the first thing you do is 'stripe' it with SMPTE timecode. It is then labelled on every centimetre of its length with a unique time value, which can later be interpreted into MIDI sync and song position pointers. Only after the striping process is complete do you think about recording any music.

This is where the big difference lies between timecode and conventional FSK tape sync. Although timecode on your tape contains positional information, it bears no relationship to your music until you define one. You have to set the start point and you have to set the tempo, and any tempo changes, on the SMPTE-MIDI device you are using.

In practice, this means that you record basic music tracks on the sequencer, list on paper the tempo and any tempo changes, then enter these into the timecode unit, along with the timecode value of the start point you want. Needless to say, it is somewhat inconvenient to have your musical data in the sequencer and your tempo data in the timecode unit, but until manufacturers start to combine the two in one box it is something that we shall have to live with - at least, I thought it was something we were going to have to live with...

IMPROVED FSK



As the saying goes, sometimes you can't see the wood for the trees. I for one had consigned any non-timecode synchronisation system to the trash-can icon of life. SMPTE seemed to be the way to go. Perhaps manufacturers were also thinking the same way, or perhaps I could speculate that they saw SMPTE as too good an earner to develop a cheaper system. MIDI timecode (MTC) is on the way of course, it's been on the way a long time and you could die waiting. In the meantime, could old-fashioned FSK tape sync be improved. What does it need to make it better and what advantages might it have over SMPTE? Let's see...

As I have outlined, the good thing about conventional FSK tape sync is that you only have one command centre - the sequencer or drum machine. You record your basic tracks on that, along with any tempo change data you choose. To record the sync track is just a matter of hooking the system up correctly, then playing back your sequence, recording the FSK pulses onto tape. The start of the FSK pulses is then automatically the start of the composition, and tempo data is determined automatically by the variation in the rate of frequency shift keying.

If it were possible to add extra data to put timing information on the tape, the FSK system would be perfect. So much simpler than timecode and probably cheaper too. Don't forget that SMPTE timecode was originally intended for synchronising audio and video recorders. Only now are we trying to graft MIDI onto it.

THE PPS-1



If you read last month's 'Inside Views' feature on Jim Cooper (who is, of course, Mr J.L. Cooper himself, designer of the PPS-1), you will be considerably enlightened - as I was - about his attitude towards 'filling in the gaps' that the major manufacturers miss out. You could call it picking up the crumbs but, as it happens, this particular 'crumb' turns out to be a rather large and tasty piece of cake.

The PPS-1, or Poor Person's SMPTE as the distributors in this country choose to describe it, is conventional FSK tape sync with bits added - digital bits which perform much the same task as SMPTE, but oriented towards the MIDI user rather than the TV studio.

The PPS-1 comes in a distinctly unflashy steel box. I haven't given it the drop test yet but I am sure it would survive. Rear connections include DC 9V In, MIDI IN, two x MIDI OUT, TO TAPE and FROM TAPE - all you need really. Top panel controls are minimal: one LED to indicate that you're plugged in to a power source, one LED to show you that you're locked onto good quality incoming code, and a three-way switch which I shall explain shortly.



"Poor Person's SMPTE... is conventional FSK tape sync with bits added - digital bits which perform much the same task as SMPTE, but oriented towards the MIDI user rather than the TV studio."


FIGURE 1. How the J.L. Cooper PPS-1 unit fits into a typical MIDI recording set-up.


Let's see how you connect up the PPS-1: Figure 1 shows how its done. There are two stages to the synchronisation procedure. After you have recorded a few basic tracks away from the tape recorder, it's time to lay the sync track on the tape.

MIDI OUT from the sequencer is connected to MIDI IN on the PPS-1 and the sequence set to play. I didn't have a lot of success in monitoring the output of a synth while laying down the sync track, as the manual suggests you can, but perhaps this is due to peculiarities of my specific set-up. If this is important to you then I suggest you check with the distributor. I didn't find it too much of a hardship not to be able to monitor while laying down the sync code because it successfully removed the temptation to lay down music tracks at the same time. Doing this can result in tracks ending up a few milliseconds out of true, which can often be enough to upset the whole feel of the song.

Having recorded the sync track, you have to replug the system (which is a bit of a bore) into the FROM TAPE configuration. A MIDI patchbay would help here. To get started with the real business of recording, just slide the front panel switch to the appropriate FROM TAPE position and you're off. Wherever you go on the tape, your sequencer will follow, taking just a couple of seconds to catch up. MIDI Start and Continue codes are sent as necessary and since changes in tempo are now written into the sync code, the sequencer will slow down and speed up automatically.

THREE POSITIONS



I ought to elaborate on the three-position switch on the top panel. Obviously, this switches between 'record sync to tape' and 'read sync from tape', respectively labelled TO TAPE and FROM TAPE. Less obvious is the need for two FROM TAPE switch positions. The manual explains, not very well but I understand what it's getting at. Apparently, some sequencers and drum machines are a little slow in their thought processes - in fact, if you throw too much data at them too quickly they will just shut up shop and say 'I've had enough!' Other sequencers have high IQs and can respond quickly to new instructions.

To get the best out of both sequencer types there is a FAST setting and a SLOW setting on the PPS-1. In FAST, synchronisation lock is achieved very quickly with a quick-thinking sequencer; in SLOW, a waiting period is inserted automatically so that the sequencer has time to do its bookkeeping. According to the manual, machines which require the SLOW setting include the Yamaha QX5 sequencer - of which I just happen to own a specimen, as a backup to my currently favoured software system. I have commented on the QX5's difficulty with MIDI song position pointers before so I will not go into it again here, except to say that it only concerns record mode, playback is fine. I tried the QX5 on both SLOW and FAST settings of the PPS-1 and found no difficulty, using SLOW just meant that things took longer. The PPS-1 manual lists three other machines which may have this problem, but since I don't have them to hand to check them out I think it would be a little unfair for me to name names on someone else's say-so.

PERFORMANCE



With a simple device like the J.L. Cooper PPS-1, one might be tempted to write a review which says 'Yes, it works' and leave it at that. The facts of life are that there always seems to be something to say about even the most unassuming piece of equipment.

The PPS-1 does work, and could well find its way onto my shopping list in the near future. The only possible query could be the robustness of the sync pulse - how well it stands up to crosstalk from the adjacent track. I tried putting some nasty bass frequencies on tape, which tend to 'spread', and at high level they did tend to affect synchronisation, but no more so than any other synchroniser I have tried. I would in practice be happy to record any instrument, apart from very bassy sounds, on track seven of my half-inch 8-track recorder. The code itself, being a lower frequency, is less troublesome than SMPTE and causes less crosstalk, which is another plus point.

According to the manual, the code used has enough bits to cope with over two hours worth of recording time at 120 beats per second. Given that they probably mean beats per minute, this would seem to be enough for most musical purposes - unless you're into opera!

There isn't a piece of equipment on the market that doesn't have a few problems and the PPS-1 is no exception. They are fairly small problems but since the only true goal in life for a manufacturer ought to be perfection, I have no real hesitation in pointing them out.

First and foremost is the Taiwanese mains adaptor. The transformer and two-pin mains plug are in one plastic moulding, and when plugged via a three-pin adaptor into the mains they make an exceedingly top-heavy unit. I very much hope that Mr Cooper will find a better supplier for this item.

Second problem is the output level of the sync tone. I measured it at around 200 millivolts peak-to-peak, which wasn't really enough for my properly lined-up -10dBu machine. Playing back at this level didn't give a satisfactory lock-up, even with new tape and clean heads. Perhaps a screwdriver-operated preset would have improved matters.

The third matter is something that most manufacturers have cottoned onto already, that internal items should not be fixed by screws which are accessible from the front panel. It looks messy and isn't necessary. Although it's only a small point here, I have seen it in its greater and more problem-inducing manifestations on other manufacturers' gear, so I'm keen to nip it in the bud.

MIDI TIMECODE



Is there anything else? Have I been hiding something which might be interesting? Well there is another feature to the PPS-1. I mentioned MIDI timecode earlier on, and I'm still waiting for Jay Chapman to write the definitive article on the subject so I'll know what it's all about, but in the J.L. Cooper PPS-1, MTC has arrived!

The PPS-1, apparently, can handle MIDI timecode - if the rest of your equipment can. By changing the position of an internal jumper, the PPS-1 can read SMPTE code and convert it into MIDI timecode. As a bonus, it can also - when reset in this way - generate SMPTE code in the 30 frames per second, non drop-frame format. The clever thing is, once you have reset the internal jumper, you can use the PPS-1 in either the ordinary tape sync mode or the MIDI timecode mode, depending on the position of the top panel switch on power-up. I wasn't able to test this feature as I don't own any gear which has the new MIDI timecode facility on it (apart from Sequential's Studio 440, such devices are presently thin on the ground), but it could come in handy in future. Who knows?

So, the conclusion, is the PPS-1 a good thing! Well, I can't figure out why nobody thought of it before, it's a great idea. I found it much simpler to use than SMPTE, because you don't have to worry about start points and tempo. It's cheaper than SMPTE too, at £228.85 you'd call it a bargain if it didn't come in such a small box.

If you're into video and all the big boys' stuff, then it has got to be SMPTE. If you're into music and MIDI, then it's got to be the J.L. Cooper PPS-1. Thanks J.L.

Price £228.85.

Contact Evenlode Soundworks, (Contact Details).


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Sequencer Plus

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The Sound On Sound Guide To Samplers


Sound On Sound - Copyright: SOS Publications Ltd.
The contents of this magazine are re-published here with the kind permission of SOS Publications Ltd.

 

Sound On Sound - Nov 1987

Gear in this article:

Synchroniser > JL Cooper > PPS1

Review by David Mellor

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