Optical Retrieval from "Touchy-Feely" Vinyl
The tactile response of a stylus tip to the terrain of vinyl walls has an analogue cousin in the movie industry – the split solar cell reader of the two squiggly lines in soundtracks. In fact, the compound etching of both linear and stratified information in a vinyl groove when viewed in its microscopy is a haunting blend of today’s linear analogue soundtrack (Dolby SVA) and the old striated Academy soundtrack standard of the late ‘20s and early ‘30s (still playable on today’s projectors).
The rub, of course, is that one was meant to be felt and the other seen by their respective sensors. This may or may not pose a performance ceiling to the recent entry of laser transcriptors that have to rely on reflective interpretation of opaque vinyl wall terrain as opposed to the more definitive reading obtained through the transparency of film stock.
But if there were to be any feasible pathway for good optical retrieval of record tracks, it would almost certainly have to incorporate fiber optics in tonearms and cartridges.
These latter day cartridges would incorporate banks of micro emitters and receptors along each side of their styli tips to transcribe the three dimensional terrain and, while we are at it, do a bit of error checking. The light would be sourced and received in an exciter supply unit “below deck”. Processing of the light signal could be greatly enhanced by digital at its best – Boolean number crunching and error checking. This kind of processing occurs with every digital movie soundtrack we currently hear to counteract film-scuffing wear. Although in our case, this processing would only define what is true groove information and rule out scratches, dust and silverfish droppings, then pass along (with no frequency response penalty) the filtered light to a split solar cell. Finally, the analogue signal passes through RIAA compensation (I’d add ffrr) and on to our favorite amp.
Immediately, two of vinyl’s arch weaknesses would fall. Channel separation would be as good as that of the lathe’s because light doesn’t emit collateral transmissions. In addition, end of record distortion whose chief cause is etched information congestion due to the reduced cutting/sampling speed (under 10 ips as compared to over 18 ips in a record’s outer grooves) could well be interpreted better from reading styli straddling wall tops than tracking styli riding out the storm.
Lastly, while most would certainly pass on John Dolby’s frequency robbing Noise Reductions, his brilliant work in eking out of four distinct channels from two optical signal tracks in SVA stereo is something to consider, especially in new pressings. Since there are no attacking helicopters from the rear in the music I listen to, I’d dispense with the surrounds. But offer me a distinct, non-summing, center channel for my LP system, and I might give it a good listen.
To be sure, this is all pipe dreaming – an escapist distraction as shadows grow across the economic lawn. Real efforts at extraction and retrieval will more likely be applied - not to the 30% of untapped musicality in records, but to the 30% remaining crude under Western Pennsylvania.
