[78-L] Removal of hiss on 78 transfers

[DAVID BURNHAM]

This optical system does not produce noiseless playback. On a worn 
record it is not such a simple thing to determine the position of the 
cutting stylus. Groove damage can make it hard to tell where the 
groove is at all using this technique, and this optical system has to 
interpolate in order to "play through" bad spots.


                        -        Jeff Lichtman
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This is, more or less, the same position that Michael Biel took when I first mentioned this concept.  I realize that there have been optical or laser 78 and LP disc players around for many years but the one I heard at the National Archives in Ottawa several years ago sounded dreadful.  It sounded like a 78 played with an LP stylus and I suspect that the laser was probably set up to play LPs and that's why it sounded like that.  But let me emphasize that the system I visualize does NOT involve playing the record at all.  The record is treated purely as a physical object.  I know that lasers are able to scan a surface microscopically so that a visually smooth area can look like a mountain range.  What I am suggesting is that the groove of a record is scanned laterally or radially, however you want to describe it.  Assuming the results of this scan to be shown on a computer screen, what you should see is a "V" in the shape of the cutting stylus.  If
 the actual shape of the cutting stylus is known, the scan can be compared to it and only the parts of the scan which coincide with the reference stylus are considered valid and other parts of the scan are disregarded.  If there is no reference shape available, it would be easy to create a reference from the record itself.  If the groove is scanned say 50,000 times per revolution, (on a 78), it should be possible to establish exactly where the cutting stylus was during the recording and even if the record has some wear, there should be no surface noise.

This system has been rattling around in my brain for about 35 years and I only wish I had the engineering skills to actually make a working system, but I don't; but at the speed technology is moving ahead today, someone will, or maybe they already have designed a system which works somehow like what I've described, producing the same results.

db