[ProAudio] Plangent playback, was: Re: FeralA - Recordings released encoded with Dolby A

John Chester jkc at jkc-lab.com
Sun Feb 9 20:02:42 EST 2020

On 2/9/20 8:48 PM, Corey Bailey Audio Engineering via ProAudio wrote:

> While I understand that you are capturing both signals during playback 
> (on yet, a different machine), aren't you assuming that the record 
> head & the erase head were in perfect agreement on the original record 
> deck?

The signal that remains on the tape is the bias signal from the record 
head, same head that's recording the audio.  Thus, the bias and the 
audio on the tape have exactly the same azimuth and the same wow and 

I don't know whether the erase head records a signal on the tape at the 
erase frequency -- I've never tried running a recorder with the record 
head disconnected.  If the erase head does record the erase frequency, 
the bias is certainly strong enough to erase that signal.

Playback is done with a head that's got wide enough bandwidth to capture 
both audio and bias with the same head.  Because both signals are 
recovered by the same gap, flutter caused by the playback machine will 
be identical for audio and bias.  Plangent processing will remove both 
the flutter of the recorder and the flutter of the playback machine.

-- John Chester

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