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Time To Get In-Sync

Fostex Synchroniser & Sync Controller

Having familiarised you hopefully with the jargon and workings of synchronisers through his 'Using Timecodes' series, Francis Rumsey now turns his critical eye to the most affordable synchroniser/controller set-up available: the Model 4030/4035 from Fostex.


The appearance of this low-cost synchroniser package from Fostex makes the linking of recorded music/soundtracks with video a viable possibility at last for those of us working to a budget. Through his 'Using Timecodes' series, Tonmeister lecturer Francis Rumsey has attempted to prepare the way for a better understanding of audio/video synchronisation in readiness for this review. So here it is...


When I first discovered the existence of a synchroniser system costing not much more than a thousand pounds, I didn't believe it. It was nevertheless true, and seems set effectively to do to the established synchroniser manufacturers what the Amstrad computer is presently doing to the IBM PC.

SYSTEM CONCEPT



The Fostex 4030/4035 combination falls neatly into the 'multiple chase synchronisers with intelligent controller' bracket, which I have outlined in Part 4 of my series Using Timecodes (see page 56). Such systems have the flexibility to allow either simple chase operation between a master and a slave with no need for a controller, or a more advanced configuration using an intelligent controller to address up to a given number of chase synchronisers (four in this case).

The 4030 Synchroniser is a 1U rack-mountable device with a minimum of display and control, information, and providing remote control synchronisation of one slave transport. Effectively, it is necessary to use one 4030 for each slave to be locked, if multi-machine systems are in use. Control of up to four 4030s is performed by the 4035 Controller, which provides for offset insertion, looping, cue memories etc, requiring an 8710 Synchroniser Interface unit between them.

On the rear panel of each 4030 Synchroniser is a DIN socket which allows for 'pseudo-RS232' communication with a host computer. Presumably they mean by this that the data format resembles RS232 but the connector is non-standard; nevertheless, this opens the door for users to develop their own controlling programs from a desk-top microcomputer, perhaps for more than four slaves, holding many more edit points than the dedicated 4035. Whether this is practical is naturally dependent on your situation and the amount of space in your control room.

4030 SYNCHRONISER



Taking a more detailed look at the chase synchroniser alone, it is clear that this is all you need for simple locking of two machines with no frills: suiting such applications as dual-multitrack lock, layback of mixed audio to video etc.

The front panel holds three status lights, these being for Valid Master Code, Valid Slave Code, and Locked: all self-explanatory. Controls are provided for Lock Enable and Chase Enable, plus a group of buttons for modifying the offset between master and slave codes by a small amount. Lock Enable seems only important if the 4030 is part of a larger system, because it brings the 4030 'on-line', but without chasing the master, while Chase Enable causes the lock-enabled slave to locate to the master timecode position (plus or minus any offset), thereafter following the master wherever it goes.

Offset alteration is allowed in the form of a 'trim' from the zero-offset position, using the Offset Modify key in conjunction with the Retard and Advance keys. A further two keys allow one to Store and Clear the modified offset, but only if Offset Modify is activated, which prevents inadvertent cancelling of the correct offset. Offset trim seems designed to be very slow (inaudible pitch change), at about one frame every ten to twenty seconds, which is annoying for lining up short sections because they're over before you've moved half a frame, but good for broadcast environments where inaudible corrections sometimes need to be made between the audio and video tapes of a simultaneous transmission in a 'live' environment.

INTERFACING TO THE 4030



Looking at the rear panel of the 4030, there are master and slave timecode inputs with 'foldback' outputs (really a 'through' link for taking timecode on elsewhere), master and slave transport connectors (parallel multi-pin), a parallel connector for the 4035 Controller, and a DIN socket for 'communication'. Switches are provided to select communication baud-rate, slave 'damping' (deceleration characteristics of slave machine during location), frequency or voltage servo-control for slave capstan, and lock conditions (known as Frame, Auto, and Sync - more on this later). LEDs indicate Tape Speed Low and High, to be used in adjustment of capstan slew limits, so that the speed of the incoming timecode does not go out of the range of the timecode reader (half to two times play speed).

The Synchroniser was designed primarily for use with Fostex tape transports, but, like everyone else before them, Fostex have opted to produce interfaces to other manufacturers' machines, with all the problems implied in such a move. Nevertheless, the 4030 seems quite flexible in its 'interfaceability', requiring little in the way of extra components to make it work with other machines.

Without any intermediate machine interface, the 4030 will accept status tallies (Stop, Play, Rwd etc) with high levels from 4 to 15 volts, low-true, while providing open-collector transport command outputs for lines having high levels of not more than 30 volts. Capstan servo control is either by variable frequency (range 2kHz-30kHz) or variable voltage (range +18V to -14V); tape tachometer pulses having rates higher than 4Hz in play mode and lower than 5kHz at maximum wind speed are acceptable. A reference signal can be taken from the master in the form of either pilot or CTL pulses between 48-60Hz, and this may serve instead of timecode in some cases. An input is provided for reference video, although it is not clear whether this allows video genlock of machines.

So far, Fostex indicate that the following interfaces may be acquired for non-Fostex devices:

Video machines:
Sony VO-5800, 5850, 5630
JVC BR-8600U, 6400TR, 5300TR, CR-6650E, 8250E, 5550E

Figure 1. Locking audio tracks to video using one slave recorder.

Panasonic NV8500
(all presumably master-only interfaces)

Audio machines:
Ampex MM-1200
Otari MTR-90,10,12, MX-70
Tascam MS-16, 388, Series 50, Series 40

Obviously, your dealer will be the best person to advise you as to what is and what is not possible.

OPERATIONAL TRIALS



The system which I tested for this review used a Sony VO-5850 video machine as the master, and an MCI JH-24 multitrack as the slave. As you will see above, the JH-24 is not on the interfactly adequate one, to allow the JH-24 to link up. I make no apologies for using the JH-24 in this review, as I happen to know their quirks intimately, and know their interface requirements too, so will take these into account. As it happens, very few of the operational problems encountered can be attributed to the JH-24. This section will deal with physical synchronisation and location, leaving the controller operations until later.

Considered as a pure chase synchroniser the 4030 does its job excellently, except for a few nasties which could easily be eliminated by further software revision.

Slave location to the master position is very accurate when chase enabled, getting closer than one second to a stopped master, and often within a few frames. Speed control over the slave while locating was achieved in this system by fast toggling between Forward and Rewind modes, proving accurate while following a moving master to within a few seconds, so that lock was quickly achieved when going back into Play. In this respect it was better than a number of other chase synchronisers which allow the slave to lurch either side of the master before exercising correction.

Synchronisation of the slave in Play mode is achieved by fairly rough handling of the capstan, slewing it up and down by up to 100% of play speed while locking: this is perhaps a little unkind to the tape, but could probably be adjusted. Two basic lock modes are allowed: Frame Lock and Sync Lock. Frame Lock looks at absolute timecode values of master and slave, endeavouring to maintain the correct offset, being a 'tight' lock which appears also to transfer master speed variations to the slave. Sync Lock ignores the absolute numerical value of the timecode, looking only at the relative phase of the master and slave codes, appearing to be a 'loose' lock which does not transfer speed variations. As such it may be useful for locking tapes which have discontinuous code, or tapes having widely differing times recorded. Auto mode tries to achieve frame lock first, then switches over to sync lock, but the change to sync lock took up to ten seconds on the system which I tested, meaning that there was a long period over which the wow+flutter of the slave was bad due to the Sony U-matic master. Sync Lock on its own is annoying, and should not be generally used because the 4030 Synchroniser latches onto the first phase-locked frame on the slave after it has reached play speed at which to lock, which may not be the programmed offset point (see further comments in the Controller section).

If the master is stopped during locked Play, the slave continues playing for about four seconds, after which it stops and relocates to the master position; likewise, the locked slave is not allowed more than four seconds away from the master on its own without the synchroniser trying to relocate it. This period would seem a little long and unnecessary if it is just a safeguard against drop-outs in master timecode which would last perhaps half a second: the Synchroniser has Stop status from the master, so it could stop the slave immediately. I suspect that the Synchroniser is designed to operate with just a feed of master code, in which case this would be the only reference for the slave, and this supports my next point, which is that the slave waits up to one and a half seconds after the master has started playing before it goes into play itself, obviously waiting until the Synchroniser indicates valid master code: this tends to mean that the slave is well behind the master when it finally plays, resulting in a rather wild lurch up to two-times play speed to catch up, and a very long lock-up time. (The 4035 Controller can get round these problems by sending Play or Stop to selected transports simultaneously).

Such points are a function of the Synchroniser, not the slave transport, so could be corrected in future updates.

Simulated timecode drop-outs on the slave while locked were handled well, with no audible pitch correction upon regaining timecode. In this respect it was better than a number of more expensive synchronisers which tend to go a little crazy if they lose code, causing the slave to get faster and faster.

4035 SYNC CONTROLLER



The Fostex Controller can handle up to four machines, and is a neat and well laid out unit, connected by a single multiway cable to the rest of the system. Once one has mastered the meanings of controls like Auto Return and Auto Play, operation is very flexible, allowing multiple loop programming, variable pre-roll, automatic drop-ins and outs, and much more.

At the top of the control panel, a single numerical display can be selected to show Master Code, Slave Code, or Offset in hours, minutes, seconds, frames, and 'sub-frames' (a single figure, presumably, being tenths of a frame). A single pushbutton cycles between all three functions, and three red LEDs indicate the selection. To the right of the display are three green LEDs duplicating the three on the front of the 4030 Synchroniser.

Figure 2. A typical multi-slave recorder setup.


Below is a numerical keypad, with Store, Recall, Clr, Plus (+) and Minus (-). Some of these keys have double functions, but the designers have sensibly avoided the need for a Shift or Extra key to access these functions, by changing the function of the key automatically when that function is required. Above the numerical keypad there are two Trim controls: one for altering the offset while locked (a duplication of the Offset Modify key on the 4030) and the other for trimming stored registers, such as offset or preroll when these are recalled.

A vertical row of controls is provided to control the looping functions, these being Zone Limit, Auto Play, Auto Return, and Auto Record, and there is a further block of controls on the right-hand side for selecting transport control, lock, chase and record enable functions for the various machines.

OPERATING THE 4035



Individual control of slave and master is possible via the machine selection and transport controls, as is use of the autolocator functions to locate machines on their own. Chase enabling machines means that there after they will follow the master everywhere, just like a chase system, but it is apparent that pressing master and slave transport selections simultaneously will improve the lock time by ensuring that commands like Play are issued to all selected machines at once.

The numerical keypad allows the entering of offsets between master and slave timecodes, although any entry on the keypad is rather laborious because of the need to move the decimal point along to the hours, minutes, frames etc window in order to enter each part of the time. Offsets may include 'sub-frames', and may be trimmed either in locked mode very slowly, or in the memory register by the Trim and +/— controls. If the display is selected to show offset, it will indicate the actual numerical distance between master and selected slave dynamically (in other words, it will show any drift).

Cue memories allow for very flexible loops to be set up, in that the amount of automation involved is very much up to the operator. Timecode values may be stored in each memory (up to ten memories), and a cycle may be set up between any two cue points using the Auto Return function, specifying the start cue and stop cue. The Locate function will locate the master to the start cue minus the preroll (up to 59 seconds), and the slaves will follow, plus or minus any offset, although herein lies a slight problem, because the Fostex Synchronisers still only act as chase synchronisers, which means that they have to wait for the master to locate and stop before they know where to stop themselves.

Putting the master into Play, having located it to the cue point, will cause the slaves to follow and lock up during the pre-roll, and here I discovered another little problem: the U-matic master was located to the preroll point by unlacing the tape and rewinding it until the cue point, at which time the transport was put into Play/Pause mode ready for pre-roll. During the rewind, CTL pulses are counted instead of timecode, and the action of unlacing and relacing the tape can cause a shift in the value of where the Synchroniser thinks the machine is, and where the timecode says it is, a problem which it only realises when it releases the U-matic VTR from Pause at the start of the preroll. At this point, the master time register jumps from its estimated time to the actual timecode off tape - a jump which may be more than three seconds, causing the slaves to realise that they're in the wrong place and try to relocate.

The subsequent lock-up period is often up to ten seconds before frame lock is achieved, and another ten seconds before sync lock (no wow and flutter transfer), so the user could find himself waiting up to twenty seconds before he can make a flutter-free locked dub. Such a problem could easily be solved by rewinding the master to a point slightly before the pre-roll park and putting it into Play up to the park point, so that it could read timecode and find out exactly where it was. The lock time would probably only be about five seconds or less in this case.

Auto Return in conjunction with Auto Play can be used to execute a loop automatically, in which the Synchroniser returns to the start of the cycle when it reaches the assigned 'end' cue and goes back into Play again. The only practical problem here is that the Controller does not wait until the slaves have also located to the start of the loop before putting the master back into play!

Within a loop, Auto Record locations may be stored in cue memories 8 and 9, to perform drop-in on record-enabled slaves. The auto-record function allows for rehearsal and execution, switching on a green LED during the section to be recorded when rehearsing. Using all the Auto functions it would thus be possible to specify a loop with a variable pre-roll, variable start and end points, and variable record drop-in and out within the loop. The Zone Limit function allows 'end of reel' locations (or others) to be stored, outside which the tape may not pass: very useful for situations in which the tape machines are in another room. A Review button will wind back five seconds and play, or wind back for as long as it is held down and then play.

Cue points may be captured 'on-the-fly' using the Store key and then picking a memory location; this is also true for record locations, zone limits etc.

SOME FINER POINTS



If one watches the offset display while the machines are locking, it is noticeable that the Locked indicator light comes on when the machines are about half a frame from actual lock, after which very gradual and inaudible trim is made to the lock, and after which the Synchroniser switches to the looser Sync Lock (assuming Auto mode is selected). If Sync Lock alone is selected then the Synchroniser will still endeavour to maintain the programmed offset in locating modes, but (as found with the 4030) will lock at the first frame it can phase-lock to once the slave has reached full play speed (which is unlikely to be at the correct offset). Selecting Frame Lock subsequently causes the slave to try and relock at the correct offset.

SUMMARY



I have reviewed this system extremely critically because it is beginning to have applications in the professional field, through the availability of professional machine interfaces, and thus must be compared with other notable models, despite its incredibly low price. Despite the problems which have been apparent in my review, I am nonetheless extremely impressed and feel that the Fostex Synchroniser will certainly give the big-boys a run for their money if the next revisions in the software can take care of some of these rather annoying bugs.

There are a few doubts in my mind about the architecture of the system, in that it does not appear to be a true network-type synchroniser, whereby each interface can store its own offsets, locate points etc. Rather, it is a set of chase synchronisers with the Controller doing most of the work, and as such probably has limited expansion capability. It would, nonetheless, be foolish to expect such sophistication in a system costing perhaps one-fifth that of similar existing devices.

Finally, I would like to thank West Heath Studios and HHB Hire & Sales for their assistance in preparing this review.

(Contact Details)


Also featuring gear in this article



Previous Article in this issue

The Synclavier

Next article in this issue

Busy Doing Nothing?


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 - May 1986

Donated by: Gavin Livingstone

>

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Gear in this article:

Synchroniser > Fostex > 4030

Synchroniser > Fostex > 4035

Review by Francis Rumsey

Previous article in this issue:

> The Synclavier

Next article in this issue:

> Busy Doing Nothing?


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