First of all, a bit of background.
I have been interested in gramophone records since I was a very young teen, and a (perhaps mediocre) EE student since three years ago.
About a month ago I came across this item. An exceedingly rare French Pathé record made around the year 1905 (
pictures attached). These records were made of a cement core and a coating of phonograph cylinder wax, in which the grooves were stamped. These were made for a very short period of time, and as you can see, as they age, different thermal coefficients cause the wax layer on these records to crack all over and crumble. As if it weren't enough, just like wax cylinders, they can be attacked by mold (these disks really don't want to exist).
Personally I've never heard of anyone who has ever found a complete, playable one.
Bits of this record continue to fall from it, as whatever is left of the ancient recording turns into shambles; however, there's still a groove on it, and looking at it through a lens I can see there seems to be sound still recorded in it. There is a surviving phonograph cylinder of the same song and performer you can listen, but it's possible it's two different recordings.
Jocelyn's Berceuse by Mary Boyer, c.1902 on cylinder:
http://cylinders.library.ucsb.edu/search.php?queryType=@attr+1=1020&num=1&start=1&query=cylinder14802Mechanical playback is off the table, as it would likely destroy both the record and the stylus, but I believe a special optical player would be more suitable for archiving this recording to a digital format.
There are optical players in the market, but they are very expensive, and they are most likely incompatible with this unusual record for various reasons which go as follows:
-The recording speed is between 90 and 100 RPM, otherwise unspecified, which is non standard.
-The grooves are vertical cut, this means the stylus vibrates up and down, instead of side to side like in normal mono records.
-The record is centre start, it plays from the label towards the rim.
-The record is badly decayed, with a dull surface, lots of cracks and chunks of it missing.
What I seek to do is to build my own optical record archiving machine, capable of producing an audio transfer from the record to a digital format, whether or not it's capable of playing it in real time is not important. The tech developed will be of value, even if this record turns out to be unrecoverable.
As I have low resources, use as much recycled and low cost parts as possible.
The mechanical matters of spinning the record, and tracking the read head over it are secondary goals, my main goal right now is to work on the read head, for which I intend to modify or otherwise re purpose read heads from CD drives.
What concerns me the most is how to recover the audio from the light reflected back from the record, and if it's possible to reverse engineer the existing sensor on a CD drive carriage for this purpose. If possible, I seek help researching these sensors.
Here
https://patents.google.com/patent/US3992593A/en is the Google Patents entry for the original optical record player, dating back to the 1970's.
One thing worth noting is the feedback system used for tracking the head, specified in the patent. I'll probably have to come up with a different method for this due to the missing chunks of the record. I think that I could use the read head to first count the grooves and calculate the groove density of the record to calculate the tracking speed afterwards.