Optical pickups and surface noise

[richardh]

There was something that occured to me the other day that I thought i'd get some views on.

I remember a while ago there was discussion about machines that used an optical pickup to play standard disks - the ultimate in record wear reduction! I remember that these type of machines were not only hyper expensive but that there were also problems with dust and dirt in the grooves spoiling the reproduction.

Anyway, the thought that I had was if you used such a machine to play a 78 rpm record would you get surface noise? After all with 78's alot of the undesirable noise is caused by two things: rumble and the abrasive action of the shellac on the needle which causes hiss.

I assume that if you used an optical pick up there would be no rumble. But is this correct?

Also, if there is no needle to rub against the abrasive shellac, would you get none of the characteristic hiss?

An intreging thought, to me at least, but would it be true? Could you use an optical pick up and expect not hiss or rumble. This assumes that you can clean 78's to the standard required to play with such a machine!

Any views on this anyone?

RJ

[MordEth]

RJ

I wonder if anyone here even has one of these machines—I remember looking at one of them online with John, and they were prohibitively expensive.

Were they more reasonable in price, I would no doubt want one, but I can see why they are not—the demand for them is low in comparison to something like a CD player, and thus they cannot manufacture in similar scale, which is what makes most consumer electronics as inexpensive as it is (economies of scale).

If anyone has had an opportunity to use/hear one of these, though, I’d be interested in hearing about it also.

— MordEth

[Wolfe]

Much of the serious rumble you find on 78's comes from the original cutting lathe, so that would have to still be present, regardless.

Not only are those optical turntables very expensive, but I heard that they require to be shipped back to the manufacterer periodially to have the lasers realigned.

[gregbogantz]

Rumble would still be heard from an optical pickup. Recorded rumble is, well, recorded along with the desired program material and would be reproduced by any proper reproducer. Rumble in the playback system is mechanically transmitted from the motor or drive system to the surface of the record which is then picked up as vibrations which are indistinguishable from the desired recorded vibrations. I assume that any modern optical player would have a sufficiently good mechanical platter drive system as to render playback-related rumble nonexistent.

Most of the surface noise in records is a result of record wear with is the deformation of the groove surface from previous playings. This damage remains in the groove and will be picked up by an optical scanner just as it is by a mechanical stylus. Optical pickups are actually MORE sensitive to surface irregularities including dust and dirt than are stylus pickups because there is nothing to push or sweep the junk out of the groove as it is played. So a good optical player should include a dust brush, preferably with anti-static properties to brush the dust out of the groove just before the optical beam scans that area.

[hillndalefan]

The worst rumble I encountered was when I was broadcasting old records years ago, and I did a show on Cliff Edwards--"Ukelele Ike". The Perfect and Pathé Actuelle records had rumble at times that was louder than the recorded sound when I reproduced them with an electric pick-up [GE VR-II]. I had to play them on my Victrola 300 and pick it up with a microphone in the horn in order to put those records on the air. Acoustical reproduction didn't respond to the rumble caused by the pantograph system dubbing a large cylinder to a lateral disc. Bob Ault

[OrthoFan]

I thought this video of an optical fiber turntable was very interesting...


[youtube]http://www.youtube.com/watch?v=CnGh7FADitg[/youtube]


but I agree, at the price they want for these, about the only customers would be libraries, museums, and a few millionaire collectors.

It's amazing, though, that hopelessly cracked and damaged records can be played.

[gregbogantz]

The above video appears to be of a different type of pickup than most of the optical ones I've seen. This system seems to use a protrusion sticking out of the glass rod that appears to physically ride in the groove and guide the pickup. This would be a simpler system than the others I've seen which are purely optical - Just as with a CD or DVD player, they have no physical contact with the record. Such systems must employ optical focus and tracking servos to keep the light beam in the groove. The upside to purely optical guidance is that those systems are even less disturbed by cracks, gouges and other big physical defects in the record.

[martinola]

I'd be interested in seeing the optical pick-up's ability to discriminate between the worn and least-worn parts of a record's groove. In the old system, I know that I can get a much cleaner signal if I can match a stylus size that rides above or below the worn part of the groove. I really haven't heard any anecdotes about that yet in the realm of optical pick-ups.

Martin