During a visit earlier this week, U47 alerted me to a fascinating article in issue 94 of Tape OP magazine.
It's describes a new process to improve/restore audio recorded on (old?) analog tapes and film. Called the Plangent Process (http://www.plangentprocesses.com) it was pioneered by Jamie Howarth. From a dictionary, the name “Plangent” refers to sound – “loud, reverberating and often melancholy”.
In essence, during the 1980’s while doing some research on tape formulations, Jamie happened upon the bias tone inevitably “embedded” on a tape during the recording process. This tone, well outside of normal hearing range, is generated in the tape deck by a very stable sine wave oscillator. Upon investigating the tone on many old tapes, he realized that it was VERY distorted in the frequency domain. These FM (frequency modulated) deviations, caused by electrical/mechanical problems in the transport mechanism (including scrape flutter) were not only evident in what we refer to today as wow and flutter (say below 40hz or so) but more insidiously, could work their way up the audio spectrum creating sidebands that would actually mix with and change the harmonic content and timing of the recorded music.
If I understand it correctly, Jamie’s Plangent Process digitizes the whole audio signal including the bias tone. It separates out this (now) FM modulated bias tone, determines it’s supposed base frequency; generates a “pure” tone at the “correct” frequency; compares this pure tone to the FM tone and generates an “error signal” which is then applied to and time corrects the audio-band information on the tape. This detection/correction process involves a tremendous amount of high-speed DSP (digital signal processing). During the development process, Jamie enlisted a number of experts to accomplish both the tape head, analog playback recording hardware design, signal filtering and DSP development.
The process has been successfully applied to “problem” analog recordings from Woody Guthrie, Grateful Dead and Neil Young as well as a number of film sound restorations. Jamie claims that “even on a well-made ‘60s or 70’s recording, it cleans out all the debris that was caused by the transport. This was a surprise. Listen to how much better and fresher the imaging is, how much more depth there is and how solid it feels”.
What’s the takeaway from this for us analog tapesters. Being a digital process, perhaps not much - BUT it IS food for thought. With the appearance of many new sources of “dubs”, and some problems reported to me, I’ve been thinking about the “dubbing quality” of the tape transfer process. With LP reissues, not many people have access to recording lathes and vinyl presses, but with tape dubbing it’s different. Fire up the Webcor’s! Maybe it’s time for a “tape transfer shootout” amongst/between “suppliers”.
Charles
It's describes a new process to improve/restore audio recorded on (old?) analog tapes and film. Called the Plangent Process (http://www.plangentprocesses.com) it was pioneered by Jamie Howarth. From a dictionary, the name “Plangent” refers to sound – “loud, reverberating and often melancholy”.
In essence, during the 1980’s while doing some research on tape formulations, Jamie happened upon the bias tone inevitably “embedded” on a tape during the recording process. This tone, well outside of normal hearing range, is generated in the tape deck by a very stable sine wave oscillator. Upon investigating the tone on many old tapes, he realized that it was VERY distorted in the frequency domain. These FM (frequency modulated) deviations, caused by electrical/mechanical problems in the transport mechanism (including scrape flutter) were not only evident in what we refer to today as wow and flutter (say below 40hz or so) but more insidiously, could work their way up the audio spectrum creating sidebands that would actually mix with and change the harmonic content and timing of the recorded music.
If I understand it correctly, Jamie’s Plangent Process digitizes the whole audio signal including the bias tone. It separates out this (now) FM modulated bias tone, determines it’s supposed base frequency; generates a “pure” tone at the “correct” frequency; compares this pure tone to the FM tone and generates an “error signal” which is then applied to and time corrects the audio-band information on the tape. This detection/correction process involves a tremendous amount of high-speed DSP (digital signal processing). During the development process, Jamie enlisted a number of experts to accomplish both the tape head, analog playback recording hardware design, signal filtering and DSP development.
The process has been successfully applied to “problem” analog recordings from Woody Guthrie, Grateful Dead and Neil Young as well as a number of film sound restorations. Jamie claims that “even on a well-made ‘60s or 70’s recording, it cleans out all the debris that was caused by the transport. This was a surprise. Listen to how much better and fresher the imaging is, how much more depth there is and how solid it feels”.
What’s the takeaway from this for us analog tapesters. Being a digital process, perhaps not much - BUT it IS food for thought. With the appearance of many new sources of “dubs”, and some problems reported to me, I’ve been thinking about the “dubbing quality” of the tape transfer process. With LP reissues, not many people have access to recording lathes and vinyl presses, but with tape dubbing it’s different. Fire up the Webcor’s! Maybe it’s time for a “tape transfer shootout” amongst/between “suppliers”.
Charles
