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Reading LPs using a flatbed scanner
googlebot
post Mar 18 2010, 17:53
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I have always thought that vinyl is a terrible concept from a physical point of view. Come on, scratching a hard needle over a plastic surface that is meant to preserve what you are trying to read? That has always made much more sense from a viewpoint of cheap mass production than musically. But you can't change history. It would be nice if one could extract the information without touching. I know that there are laser scanners at the cost of a small car. But what about DIY?

The resolution of common household scanners should already suffice to do that. The only problem is that the groove's information is encoded spatially, and household scanners cannot capture z-axis information directly. Basically it should be decodable, though, because of the groove's uniform nature. The depth should correlate to a V-shaped gradient, the side walls' slope at pos x would be the first derivative of the gradient's function at x. Has anybody ever thought or heard about this in detail?

This post has been edited by googlebot: Mar 18 2010, 18:05
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saratoga
post Mar 18 2010, 18:10
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QUOTE (googlebot @ Mar 18 2010, 12:53) *
I know that there are laser scanners at the cost of a small car. But what about DIY?


The commercial ones don't even work all that well. So I'm not sure what the point is. Just rip to digital if you're concerned about wear and store the physical disks somewhere safe.

QUOTE (googlebot @ Mar 18 2010, 12:53) *
The resolution of common household scanners should already suffice to do that. The only problem is that the groove's information is encoded spatially, and household scanners cannot capture z-axis information directly. Basically it should be decodable, though, because of the groove's uniform nature. The depth should correlate to a V-shaped gradient. Has anybody ever thought or heard about this in detail?


http://en.wikipedia.org/wiki/Laser_turntab...e_IRENE_project

Apparently you're mono only and have lousy SNR, but in principle it can be done. An optical coherence approach would work much better since you could get 3D data. Hope you got an SLD and a spectrometer handy smile.gif
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googlebot
post Mar 18 2010, 18:18
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Thanks for the interesting reference. 3D Irene sounds pretty worthwhile. A serious flaw of the flatbed scanner concept would be dust. A physical needle scratches small particles just away. A 2D reconstruction cannot easily discern dust from actual spikes, a 3D reconstruction could, though.
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Axon
post Mar 18 2010, 18:48
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Vertical modulation changes the width of the groove. Lateral modulation does not.

However, the widest point of the groove has specific flaws associated with it on some records (horns) which do not exist in the tracked groove.

Moreover, there is some anecdotal evidence that the tracking performed by a stylus serves to reduce noise in such a way that optical scanning methods cannot. The laser turntables allegedly all have noise-reduction electronics built into it - which I suppose they would not have had to do if the noise levels were comparable to regular turntables in the first place..

Optical scanning is amplitude-sensitive; electronic phonograph recording/playback is velocity sensitive. Your SNR literally goes down by 60db from 20hz to 20khz as a result. With transduction methods like strain gauge which have SNR to spare, this is not necessarily a problem.. but optical is hurting for SNR from the start.
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Knowzy
post Mar 18 2010, 19:50
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In 2002, Ofer Springer, an Israeli physics student, did just what you're suggesting- trying to make music out of scanned vinyl LPs. "The results are barely recognizable as the original music, but strangely affecting," according to a Wired Magazine article on his efforts.

You can listen to Ofer's samples on his web site and see his scanned LP images.
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krabapple
post Mar 18 2010, 22:53
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There's also this, which had a bit more institutional firepower behind it:

http://irene.lbl.gov/
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DigitalMan
post Mar 19 2010, 00:15
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Dragging a needle through the vinyl seems archaic but that is how the system was designed - so what, what's the problem you're trying to solve? Looks like a huge effort to re-create the vinyl playback system. Not everything that could be done is worth doing...

I would expect an iTunes download would work just as well or better than a scanner-based playback of a vinyl LP and be an order of magnitude easier.

Or maybe this is just a theoretical pondering, in which case I'm with you.


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Roseval
post Mar 19 2010, 00:45
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There is a turntable using a laser instead of a needle: http://www.elpj.com/


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krabapple
post Mar 19 2010, 04:38
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QUOTE (Roseval @ Mar 18 2010, 18:45) *
There is a turntable using a laser instead of a needle: http://www.elpj.com/



yes, and if the record isn't spotless, the laser will read dirt as noise, just as a needle would.

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JacksonGrey
post Mar 19 2010, 05:15
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QUOTE (Knowzy @ Mar 18 2010, 18:50) *
In 2002, Ofer Springer, an Israeli physics student, did just what you're suggesting- trying to make music out of scanned vinyl LPs. "The results are barely recognizable as the original music, but strangely affecting," according to a Wired Magazine article on his efforts.

You can listen to Ofer's samples on his web site and see his scanned LP images.


Absolutely incredible, what a fantastic effort. ohmy.gif
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odigg
post Mar 24 2010, 15:58
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I wonder if you could use something like an Ultrasonic tape measure to measure the depth of the groove? Of course you'd need a device that can measure the small distances in the grooves and so a Ultrasonic device may not be suitable for that.

Is there a device like an MRI that can perform a 3D scan on the disc? Of course MRI would not work on a non-magnetic disc...

This post has been edited by odigg: Mar 24 2010, 15:59
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Roseval
post Mar 24 2010, 16:10
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QUOTE (odigg @ Mar 24 2010, 15:58) *
Of course MRI would not work on a non-magnetic disc...


Don't worry, they are magnetic as hell. In fact so horribly magnetic that they need to be demagnetized!
For only $2,252.00 the problem is solved!

Enjoy: http://furutech.com/a2008/product2.asp?prodNo=242


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Arnold B. Kruege...
post Apr 6 2010, 13:30
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QUOTE (krabapple @ Mar 18 2010, 23:38) *
QUOTE (Roseval @ Mar 18 2010, 18:45) *
There is a turntable using a laser instead of a needle: http://www.elpj.com/



yes, and if the record isn't spotless, the laser will read dirt as noise, just as a needle would.


Actually, the laser is far more affected by dust, as the needle usually either pushes it out of the way or mashes it down. The laser beam does not have a suffiicent density of photons to deal with dust. Common wisdom is that the ELP is pretty useless without a PC software to deal with the vastly increased density of tics and pops.

Remember that most household dust is said to be flakes of skin and skin mites, so its pretty soft and mashes pretty easily. TMI, right? ;-)
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