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Removing the Wow and Flutter
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If you are a broadcast engineer, it may have been some time
since you to deal with “tape.” (You remember tape — that long, thin, brown
stuff, shiny on one side and less shiny on another, that went round and round.
In various appearances it might be on a reel or in a cassette, and used with proper
machinery, usually heavy, it reproduced or recorded useful sounds. Ah tape …)
The NAB Radio TechCheck newsletter has tape on its mind this
week. The engineers at NAB have put their editorial spotlight on Plangent Processes, proclaimed
to be “quite simply the finest magnetic tape and film playback system in the
world today,” at least according to the company, which probably doesn’t have
much competition these days. But it does sound impressive.
The Plangent approach is aimed at archiving, restoration and
remastering professionals. Radio TechCheck reports that the process is being
used by record labels, film studios, producers and artists but imagines that it
could prove useful for legacy broadcast recordings as well.
NAB explains that by using playback heads with a very wide
response band, wide enough to pick up the original bias used in the recording,
and superior mechanical tape transports and pathways, Plangent Processes seeks
to eliminate wow, flutter and other distortions (physical and electronic) that
may be affecting the tape (many recorded originally, not due to age or
deterioration). Having the ability to “see” or “hear” the original bias is part
of the process.
Plangent Processes states, “All we do is reclock the
recorded signal to remove jitter and intermodulation distortion.” A little DSP
magic helps as well. Ultimately a very “clean” reproduction from an old tape
can be turned into a digital file for safekeeping and further restoration work.
The company provides an interesting explanation of the
process here.
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