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Hi Mike and others, My recollection is that Walter Welch used his two Edison players synchronized but 1/4 revolution apart to play identical records with what was supposed to be an enhancing effect and what was, memory says, certainly an interesting effect. He may well have also played records synchronized exactly. Best, Richard -----Original Message----- From: Association for Recorded Sound Discussion List [mailto:[log in to unmask]] On Behalf Of Michael Biel Sent: Friday, June 22, 2012 11:14 AM To: [log in to unmask] Subject: Re: [ARSCLIST] multiple copies for surface noise reduction, was Re: audio from pictures > I proposed a stack of tables all powered by a single motor for > playing the discs simultaneously, with use of digital delay lines > to align the audio from them after transferring. Doug's idea is not original. There was an acoustical player with about ten turntables with their own tone arms and horns stacked up on a single spindle. I think it was illustrated in From Tinfoil to Stereo. The author of this, Walter Welch came up with a simpler solution to playing two identical records simultaneously with perfect synchronization. He rigged up an electric motor on a long shaft which connects to the spindles of two Edison Diamond Disc machines with their spring motors disengaged. Multiple film machines are easily synchronized using three-phase motors locked together, but these are sprocketed and the films can't slip like tape can. Tapes can be synced using SMPTE time code, but turntables might not run at exact speeds unless the motors are also locked. Mike Biel [log in to unmask] -------- Original Message -------- Subject: [ARSCLIST] multiple copies for surface noise reduction, was Re: audio from pictures From: Doug Pomeroy <[log in to unmask]> Date: Fri, June 22, 2012 10:30 am To: [log in to unmask] > >> Date: Wed, 20 Jun 2012 10:44:42 +0100 >> From: Ted Kendall <[log in to unmask]> >> Subject: Re: audio from pictures >> >> <<SNIP>> >> >> Chris Hicks of Cedar did his doctorate on just this question of >> multiple >> copies. When the algorithm could be persuaded to work, the results >> were >> much as you would expect - enhancement of the correlated wanted >> signal >> and reduction of the random noise. Unfortunately, pulling the >> recordings >> into good enough sync for artifacts to be negligible was a >> frustrating >> 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 >> same >> afternoon, with meticulous centring. The minute geometrical >> differences >> 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 >> side >> 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 1997. Two perfectly synchronized copies would provide a theoretical signal- to-noise improvement of 3 dB, four copies an improvement of 6 dB and eight copies an improvement of 9 dB. The first problem is finding so many copies in E condition. But the bigger problem is how to achieve perfect synchronization. John S Allen of the Boston Audio Society discusses this matter in an article he wrote for the Spring 1990 issue of the ARSC Journal. He says the accuracy of sync must be "about ten microseconds (72 degrees of phase shift at 20 kHz)". No real-world turntable is stable enough to achieve this result on successive plays, and I proposed a stack of tables all powered by a single motor for playing the discs simultaneously, with use of digital delay lines to align the audio from them after transferring. Discs which are even slightly out-of-round would need to be matched perfectly 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 correcting" software might be used to help deal with alignment variables such as this. Doug Pomeroy