Decca 2

IVC Video transport type 826P.

Well this may look very much like an IVC video tape recorder on the outside, but that ain't no
video recorder! For unlike those manufacturers who inserted their audio data stream into a
composite video signal that could be recorded on a standard video machine, Decca changed their
work horse IVC video recorders to 'directly record digital frames of bi-phase modulated digital
data'. This was done by replacing the mod/demod boards and the colour adapter with their own
special 'home made' electronics. Normal composite syncs were inserted to allow the machine's
servos to have something to lock to. But otherwise this really is a digital tape recorder,

Bolted underneath the machine is a rather impressive compartment containing what looks like a
microprocessor based transport remote control interface.

Inside the machine, the tape counter roller assembly has had an optical encoder attached to its
rear end.

These modifications, which were done by IVC in Reading for Decca, enabled the machine to
work with 'modern' (well at least before these non-linear days) 9 pin RS-422 serial video editing
controllers.

(The black switch protector on the front casing of this machine is my own addition to protect a
very vulnerable tape type change over switch.) These machines can use both Ampex 191 and 3M
491 tape on 9 Inch reels, which gives a running time of slightly over and hour. Decca didn't
bother using their recorders with front covers on mostly, and the one I fitted to this machine is
borrowed from a 'standard' 826p video recorder.)

Oh, and the signals going in and coming out of this beast look nothing at all like video...

Because of the 'racket' IVC machines make (two large induction motors plus a cooling fan all
whirring away at high speed), when on location they were probably placed well away from the
proceedings. They communicated with the rest of the World by means of a 9 pin serial interface
and three 75 ohm coaxial cables - digital input, output and word clock.

(Under this machine you can see a pair of early Decca digital audio converters, but they are un-
tested and their condition is unknown).

IVC made three grades of 1 inch video tape recorders. They all had very similar transports of
the same mechanical format, which allowed tapes recorded on one machine to be played on any
of the other versions. The differences were to do with refinements, such as improved
electronics, better bearings, still frame, confidence video or better quality editing. The most
sophisticated machines (before the ill-fated 9,000 and 1-10 machines) were the 900 series, and
these large machines were mostly intended for television broadcast use (the BBC used a few of
them for local news). The 826 model as used by Decca was a 'middle of the range' industrial
recorder and was ideally suited to heavy duty day in day out working. And similar machines
were often to be found in an educational or medical TV environments. It also is fitted an extra
video head to allow off-tape video monitoring, which allowed in this case the Decca engineers
to make sure that there would be no unpleasant surprises back at base. (This 'confidence replay'
as it was known in video circles, was not available on any of the other early digital audio
systems with sometimes very unfortunate consequences!) This machine is also fitted with a form
of simple automatic tracking (possibly by Decca).

In those days videocassette were well in the future (and were never very much better anyway
until the arrival of Betacam), they were also very slow to use with all that lacing and un-lacing,
and so the next step up from one of these IVC recorders was a Ł30,000+ broadcast Quadruplex
machine. And those would have been a nightmare... So using IVCs was perhaps a rather obvious
choice at the time.

A typical IVC 800 series monochrome recorder cost rather more than Ł2,000 in 1974, or say
around Ł18,000 in today's money. Still quite expensive though.