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Re: Dead FM Broadcasting Technologies

Dolby A was the professional format used in studio recordings, professional
(broadcast) recorders and motion pictures.  It broke the audio spectrum into
four bands; high, mid-high, mid-low, and low and compressed them
individually.  It was very level sensitive and, if either or both the encode
(record) and/or decode (playback) were not properly calibrated, it did
strange stuff to your tonal quality. On most mediums, such as film and/or
recording tape, it brought the medium from a s/n ratio of 25db to 50db.  By
contrast, the consumer format, Dolby B only used a single band of
compression on the high end.

Dolby later released a format called SR (Spectral Recording) as a last ditch
effort to hold market share in a digital world.  The Cat 280 SR
encode/decode cards were made to be pin compatible with the Cat 22 A cards.
This way if you had a 24 track studio with 24 tracks of A, you could be
enticed to buy 24 Cat 280 cards to give your analog studio near digital
quality without the expense of the early digital equipment.  SR, when
properly calibrated, would give the aforementioned formats about 90db of
s/n.  It used the same four fixed bands of compression that A did plus 4
more "floating" bands that would slide up and down as needed.

NB - SR (spectral recording) is not to be confused with SR-D which is the
Dolby Digital format for cinema.  It is a common practice, however, for
movies recorded in the SR-D digital format to have the backup analog track
encoded in SR.


Brian T. Vita, President
Cinema Service & Supply, Inc.
75 Walnut St. - Ste 4
Peabody, MA  01960-5626 USA
Sales: (800)231-8849/Sales Fax (800)329-2775
Bus Ofc +1-978-538-7575/Business Ofc Fax +1-978-538-7550
----- Original Message -----
From: "A. Joseph Ross" <lawyer@attorneyross.com>
To: "Larry Lovering" <larry.lovering@cox.net>; "Garrett Wollman"
Cc: <bri@bostonradio.org>
Sent: Friday, November 29, 2002 11:38 PM
Subject: RE: Dead FM Broadcasting Technologies

> On 29 Nov 2002 at 16:22, Garrett Wollman wrote:
> > The Dolby B system for audiotape worked like this:
> Was there ever a Dolby A?
> --
> A. Joseph Ross, J.D.                           617.367.0468
>  15 Court Square, Suite 210                 lawyer@attorneyross.com
> Boston, MA 02108-2503                    http://www.attorneyross.com