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Friendchip SRC/AT

MIDI Synchroniser

It's not the cheapest synchroniser money can buy, but it's sophisticated and flexible enough to become one of the most popular. Vic Leonard gets in sync.


Away from the recent proliferation of budget-level synchronisers, Friendchip, manufacturers of the industry-standard SRC, have developed an upmarket unit with facilities to match.


THE QUESTION OF how to lock up a sequencer to a tape machine has been with us for some time now, and no sooner has one method become acceptable than another rears its head. Audio click, DIN sync and FSK have all had their day and, finally, the audio industry appears to have settled on SMPTE to MIDI Song Position Pointer converters as the norm. The code on the tape specifies the position in hours, minutes and seconds and so ensures that the sequencer is in sync with the tape machine when it starts to play - consequently, the tape can be run from any position. SMPTE was designed for use in the film and video industries and has four formats, any of which can be used in a solely musical context.

A comparative review of synchronisers in a professional periodical concluded that it is inadvisable to change the make of a converter once one has been used, for the following reason; different converters have different tempo resolutions, and as tempo changes are programmed in via a table, timing errors will be caused due to the way in which the decimal places are rounded. Not to dwell too much on the mathematics involved, it is quite conceivable that a cumulative delay of one second can occur in a four-minute song. Obviously this would be totally unacceptable.

Description



THE SRC/AT IS a 1U-high rackmount, with a front panel consisting of two key pads and a backlit display with two rows of 16 characters. The left-hand keys allow for cursor movement, number increment/decrement, C (clear/continue) and E (enter/start). The right hand pad has six function/mode keys arranged as follows:

TEMPO EDIT SMPTE DATA SONG
LEARN UPDATE CUES A< AUX >B SHIFT

The bottom row is selected by holding down the shift button and is indicated by a small LED in the top left hand corner of the shift button.

The rear panel has SMPTE in and out for connection to a tape machine, audio input, footswitch and window and click outputs as well as MIDI sockets for keyboard connection, slave out for transmitting MIDI-clock, song pointer and MIDI time code, computer in/out, the latter of which merges the internally created data with the keyboard in information, and no less than four MIDI Thrus.

Basic Operation



ON POWER UP you are greeted with the usual "fanfare" of flashing LEDs and a display which ends up with "SRC-AT: The Best Synchroniser" - arrogant or what?

Each function has its own menu which can be scrolled through and one page selected. The cursor can then be moved around that page and the +/- keys can change relevant data.

Let's take a wander through a typical session and assume that the sequencing has been completed. Select SMPTE mode and set the format - from the four standard options - before starting the generator and recording the code to tape on track one or 16 at about -6dB for the length of the song. Tempo mode then allows the particular layout of the song to be entered - changes of time signature and tempo in steps of between a 16th and a quarter note, and as 999 tempo changes are permitted, you're unlikely to run out. Key in the song length in Edit mode and a swift push of the Song mode button sets the SRC/AT into computing the SMPTE times for each step. In fact, the machine will run on its own internal clock, allowing you to check out the sequencing without being locked to tape, and any alterations can be made in Update mode by moving the SMPTE time for any step.

Should you then decide that parts of the sequencing have to be changed, simply go into Edit mode and use the Copy, Insert, Delete and Clear functions. Finally, should you wish to drop in at certain places, Cue mode allows cues to be set up.

Imagine for a moment that you now find the song is, say, 15 seconds too long. Time to start again? No, the SRC/AT has the ability to change the total time of a song by expressing it as a percentage of the original and alters all tempo changes accordingly. Life saver.

Applications



THE PRINCIPAL USE of this device is to record a time code onto tape and to then lock a sequencer to that code on playback. However, there are units costing less than a third of the price of the AT which will adequately do this, so why splash out on the SRC/AT?

One function that this unit possesses is of immense power - that of "learning" a song by either reading the clock from an external MIDI device or by timing pulses from an audio source. In fact, it can read other tape sync codes, such as DIN sync, by treating them as audio signals and feeding them via the audio in. The SRC/AT will time the gaps between consecutive clocks/pulses and tabulate them. This takes place in Learn mode and can be edited or corrected in Update mode by changing the SMPTE time of a step, hence altering the tempo of the previous step - neat. More to the point, it doesn't count these as being actual tempo changes, and so 999 bars can be input effectively with 16 tempo changes per bar.

The only problem with this is that the signal arriving at the audio input must be both percussive and clear or else false triggering will occur. To aid this, the AT uses a gating system, whereby the window stays open for a percentage of the time between two beats and then the shutters come down for the remainder, muting the input. This is of particular use when drums are mixed onto a track or where the only version of a song is on a two-track master. As an example, if the window is set to 5%, then it will open for 5% of the time between two pulses and, if no pulse is received within this time, will stay open again for further multiples of 5% until a pulse appears - an approximate tempo has to be set in the first instance. Once a pulse has appeared, the window closes for 95% of the estimated time for the next pulse and then opens again. At 120bpm, a 5% window will open for 25 milliseconds during which the pulse needs to appear if the window is to then close.

Getting this percentage right takes a fair bit of trial and error - more of the latter to begin with in my case - but one useful feature is that the pulse generated appears at the click output and can be patched into the audio system, making judgement of the window size a much easier task. It also provides the drive for non-MIDI drum machines and the like with a rate adjustable from one pulse-per-four-beats down to 24 pulses-per-quarter-note.

The main point to realise here is that the larger the changes that occur in the tempo, the longer the window has to stay open which leads to a higher percentage figure.

You can play in a song from a sequencer complete with tempo changes and it will also be learnt by the AT. This is an alternative to setting up the tempo changes in Tempo mode - and it's much quicker.

On test, typical lock-up time was about two seconds and I was quite amazed at what this machine could do, trying it with various styles of music. The first thing to do was to choose which percussive instrument to trigger the AT from, by deciding which one exhibited the most regular pattern - the snare was usually a good bet although good results were also obtained by using bass drum, hi-hat or rimshot. If the instrument doesn't play on the beat of the bar, then you can simply offset the code to allow for this. I did succeed in confusing the poor AT when driving the audio from a stereo mixdown but, again, it came down to getting the window time right.

For triggering from a live drum kit, acoustic or Simmons, the AT can only be described as absolutely wicked. It gives the same kind of results as the Kahler Human Clock, and could be used live to allow the drummer to drive a sequencer. The human feel is subtle but really does take the rigidity out of the music. There's more: connect any source capable of producing an audio signal (I used an old acoustic guitar pickup) and tap in the rhythm. Again, you can listen to the click or see the LEDs on the tempo and shift buttons flashing on the beat.

Running timecode on tape is a less than perfect way of doing things, and occasionally the unthinkable happens and you get a dropout. The AT can generate its own internal frame count from the point at which the SMPTE input stops and defaults to ten frames - something just less than half a second. OK, this doesn't dub the code back on to tape but it does prevent you having to do so. If the song happens to be going through a tight set of tempo changes, then some alteration of the tempo table may be necessary. Alternatively, you can reassign the sync position of the next measure.

Coding Accuracy



IN THE INTRODUCTION I mentioned sticking to the same synchroniser to avoid compatibility problems. But the high tempo resolution of this machine ensures that there will never be more than one millisecond of inaccuracy over the duration of a four-minute song. If another converter has inaccurately sync'd up the sequencer to the tape machine, replacing it with the SRC/AT will not correct what's already on tape even though what will be recorded will now be spot on. One alternative would be to read one of the percussive instruments into the AT and recreate the conversion.

It's good to see that song data can be sent to the sequencer via SysEx and reloaded into the SRC/AT at the beginning of a song. I was impressed to find Friendchip appreciated that not all sequencers have the ability to record SysEx and have implemented a save facility using a string of note on and offs which will then be decoded when sent back. Saved data by either means can be verified by running it back into the AT.

Verdict



THERE IS NO doubt that this is a machine of the highest professional quality which offers facilities above and beyond the all of duty. It comes with an excellent manual full of notes, tables and even a basic computer language program to help sort out sync positions at various tempos.

Even the price isn't high when compared with machines like the RTL Event and the SMP24. But it is fair to say that should you only intend to use it for straight time coding, then much cheaper alternatives do exist.

Price £699 including VAT

(Contact Details)


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Previous Article in this issue

Music TV

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World Machine


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

 

Music Technology - Nov 1988

Gear in this article:

Synchroniser > Friendchip > SRC/AT

Review by Vic Lennard

Previous article in this issue:

> Music TV

Next article in this issue:

> World Machine


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