Maintaining Audio Quality in the Broadcast Facility 2011 - Orban

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Maintaining Audio Quality
being manufactured. Before considering use of old stock of these tapes for new recordings,
be aware that several suffered from “sticky-shed syndrome” (see page 65)
and may have deteriorated severely since they were manufactured. It is safer to use
newly manufactured tape for new recordings.
In 2006, Recorded Media Group International (RMGI) in the Netherlands began
manufacturing EMTEC specification tape in Oosterhout. ATR Magnetics of York, PA,
longtime service and modification shop for multitrack and master recorders, began
manufacturing analog multitrack tape, and in November 2006 began beta testing a
new formula. Jai Electronic Industries in India is currently making audio tape in
6.35 mm (1/4") and 12.7 mm (1/2") width, and perforated 16 mm and 35 mm audio
tape for the film industry. Daniel Technology in the USA are making 3.81 mm tape
for the Nagra SN-series tape recorders. Pyral in France are making perforated
16 mm, 17.5 mm and 35 mm audio tape. 18
Tape Speed:
If all aspects of the disk-to-tape transfer receive proper care, then the difference in
quality between 15ips (38cm/sec) and 7.5ips (19cm/sec) recording is easily audible.
15ips has far superior high-frequency headroom. The effects of drop-outs and tape
irregularity are also reduced, and the effects of interchannel phase shifts are halved.
However, a playback machine can deteriorate (due to oxide build-up on the heads
or incorrect azimuth) far more severely at 15ips than at 7.5ips before an audible
change occurs in audio quality.
Noise Reduction:
,A compander-type (encode/decode) noise reduction system can be used to reduce
tape hiss to an unobtrusive or even inaudible level. However, if transparency is desired,
it is difficult to imagine a contemporary broadcast application where companded
analog tape would be preferred to linear PCM digital recording, which is
reliably transparent when implemented correctly. In contemporary production, tape
is usually used because it colors the sound in a way that artists and producers find
attractive. Tape hiss, soft saturation, and modulation noise are part of that color.
Because 7.5 ips introduces more high-frequency saturation than 15 ips, the production
community has found both speeds to be useful for different effects.
However, compander technology is still of interest because many legacy recordings
were recorded using a compander-type noise reduction system and correct playback
requires access to the compander hardware or a digital model of it. We have evaluated
and can enthusiastically recommend Dolby SR (Spectral Recording). Good results
have been reported with Telcom C4 as well. dbx Type II noise reduction is also
effective and has the advantages of economy and freedom from mistracking due to
level mismatches between record and playback. Dolby A was the original multiband
compander and many legacy recordings were recorded using the Dolby A system,
which provides modest amounts of noise reduction but no audible noise pumping or
breathing when properly aligned.
18 http://en.wikipedia.org/wiki/Reel-to-reel_audio_tape_recording