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Removing the Wow and Flutter

Tape recording restoration brings the bias out

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.