Re: [ARSCLIST] Optical Groove Digitization

[Steven Smolian <smolians@xxxxxxxxx>]

It's not just anti-skating.

Every cartridge is designed to swing from left-to-right and back to the
excursion required by a stereo record.  A three mill groove requires the
cantalever to swing six times as far in both directions from the same pivot
point.

The weight of the diamond is greater.

The amount of downward force is greater by approximately 2-1/2 times to keep
the stylus from being thrown out of the groove.

The cutting angle of 78s was 0 degrees, that of LPs, 15 degrees.

The problem may not be anti-skate.

Steven Smolian

----- Original Message -----
From: "Rob Spencer" <rspencer11@xxxxxxxxxxx>
To: <ARSCLIST@xxxxxxxxxxxx>
Sent: Friday, September 26, 2003 2:53 PM
Subject: Re: [ARSCLIST] Optical Groove Digitization


> Duane Goldman wrote,
>
>  > As an eternal devil's advocate I still ponder the concept of
>  > translating a continuous 3-D analog signal into a digital
>  > representation . . . many educated ears are not satisfied with
>  > digital reproduction. . . Perhaps in concert with such efforts
>  > {at 3-D scanning] should be an equal expenditure to improve
>  > analog recording & reproduction if for no other reason as to
>  > establish a proper base point.
>
> As always, Dr. Goldman brings up points worth pondering, especially as
> regards the reproduction of coarse-grooved records.  Wouldn't it be nice
> to have a turntable/arm combination specifically engineered for 78
> playback, as opposed to microgroove?  With proper anti-skating, at least?
>
> More interesting is the question of digitization of the signal.  It
> seems to me that the process of producing a highly accurate 3-D digital
> image of the surface of a record does not digitize the signal, merely
> the physical analogue of the signal as represented by the groove on the
> record.
>
> In fact, the signal need not be digitized at all with this process,
> whether the virtual groove is tracked virtually or used to produce a new
> copy of the record for traditional playback (both options have been
> discussed on this list).  It can be kept in analog form.  One may argue
> that digitizing the record surface perforce digitizes the signal, but if
> the accuracy is high enough it seems to me that there would be no effect
> on the signal itself.
>
> In any event, the typical pre-tape 78 was recorded direct to disk, ore
> or less, so unless there is access to the original metal parts or an
> intermediate form, the record itself is the lowest-generation copy
> available, so we are faced with the necessity of tracing its groove in
> one way or another.  In theory, the process discussed herein would seem
> to allow the most accurate extraction possible of the information
> represented by the groove.  At the least, it would allow the
> reconstruction of a mint copy of any record that has a groove that is
> pristine at some level all along its length.  This last consideration
> alone is enough to justify it for me.
>
>
>
> Rob Spencer