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[Project Gramophone cc'd] Kurt Nauck wrote: > Have you seen this? > > http://www.eif.ch/visualaudio/ > > Perhaps now the tinfoil playback problem has been solved! > > There is a description of this system in the July 2003 IASA Journal. > Fax: (425) 930-6862 I've been intrigued for a long time with "optical" methods to preserve and to recover the "sound in the grooves." This work is definitely the next step in the right direction. My current thinking, however, for the most advanced playback of older recordings is to get a true, high resolution, 3-D characterization of the entire record. In essence, to create a very precise topographic "map" of the record. This way, the full information of the recording is preserved, and it may be possible, using a super-computer and the right algorithms, to do the highest possible quality "transfer" of the recording (interestingly, one may be able to precisely correct for complex warping of the records.) The problem with the current playback methods, such as a stylus running in the groove or the optical method noted in the article described above, is that they still "linearize" and mix information together, and once one does that, one loses a lot of information that otherwise will be useful for the best possible restoration. With the 3-D topographic approach, in principle one should be able to best ascertain what the original signal was based on full analysis of both walls of the groove, from the top of the record to the bottom of the groove. It may be possible to recover the original signal from some types of groove damage, and to minimize the effects of nicks and impurities in the record substrate (e.g., the abrasive particles records used to use to polish the steel playback needle -- these stick out like boulders in the groove path.) Of course, some challenges to this 3-D topographic approach are: 1) Huge amount of data: To get adequate 3-D resolution will require sampling a *lot* of data -- I haven't figured it out yet, but we are talking about many gigs at the minimum for a typical 10" 78rpm disc. (But disk space nowadays is readily available.) 2) Coming up with the program and requisite algorithms to analyze the data. It would not surprise me that it would take a super-computer (such as a cluster of PC's) several hours to extract the optimized signal from the grooves (if this is the case, then this project could tap the huge reservoir of volunteer pc's out there, such as what Project SETI uses.) Maybe I'm being overly pessimistic, and that in the distant future this can be done quite fast and by the "ordinary" restoration engineer. 3) And of course, how to actually scan for this data. There is no doubt equipment/techniques that will do this, but it is unknown if there is any "commercial" equipment that does this (there might be); rather, it may still be in the province of advanced research at places such as the National Labs, for example (I used to work as an engineer at Lawrence Livermore Laboratory, and making high resolution 3-D "topographic" maps of surfaces is something that someone there may have expertise in -- one of these days I plan to check if this is so.) Just my $0.02 worth. Jon Noring