>> Date: Wed, 20 Jun 2012 10:44:42 +0100
>> From: Ted Kendall <[log in to unmask]>
>> Subject: Re: audio from pictures
>> Chris Hicks of Cedar did his doctorate on just this question of
>> copies. When the algorithm could be persuaded to work, the results
>> much as you would expect - enhancement of the correlated wanted
>> and reduction of the random noise. Unfortunately, pulling the
>> into good enough sync for artifacts to be negligible was a
>> and difficult business, even with recordings made one after the other
>> (by me, as it happens) on the same kit on the same settings on the
>> afternoon, with meticulous centring. The minute geometrical
>> between different laminated pressings were enough to throw things
>> continually out of register. The example produced, however, is a
>> tantalising glimpse of what might one day be possible.
>> Whenever I do a master of the QHCF Decca of "Souvenirs", I use three
>> copies from the shelf - one for the very start, one for most of the
>> and one for the last few turns where the others are afflicted with
>> "Decca scrunch".
I gave a talk on this subject at the ARSC conference in Nashville in
Two perfectly synchronized copies would provide a theoretical signal-
improvement of 3 dB, four copies an improvement of 6 dB and eight
improvement of 9 dB. The first problem is finding so many copies in E
But the bigger problem is how to achieve perfect synchronization.
John S Allen of the Boston Audio Society discusses this matter in an
wrote for the Spring 1990 issue of the ARSC Journal. He says the
sync must be "about ten microseconds (72 degrees of phase shift at 20
No real-world turntable is stable enough to achieve this result on
plays, and I proposed a stack of tables all powered by a single motor
playing the discs simultaneously, with use of digital delay lines to
the audio from them after transferring.
Discs which are even slightly out-of-round would need to be matched
with others of the same shape (not impossible, since these discs
reflect the shape
of the metal stamper used to press them), and digital "azimuth
might be used to help deal with alignment variables such as this.
Audio Restoration & Mastering Services
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