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Re: [ARSCLIST] Dolby S/N Stretcher
Tom,
Actually, the DBX process is not level sensitive, as it employs a direct
2:1 linear companding system. This was the big advantage of DBX over
Dolby, which is level (and response) sensitive (in all it's flavors).
The biggest issue with DBX was the "breathing" artifacts that were
frequently apparent in quiet passages, due to the aggressive amount of
noise reduction the system attempted to achieve. This was sometime less
apparent in the type II format, depending on how linear the
recording/reproduction chain was. If the overall frequency response was
not flat, things could get rather bizarre.
Although the system could theoretically achieve about 120 db of dynamic
range, most recordings could never even come close to this figure, due
to the noise generated in the stages just ahead of the compander. If
David Blackmer (the designer) had maybe gone for a little more gentle
companding slope, they still could of achieved some significant noise
reduction, without the accompanying artifacts. All this has of course
now become just another fascinating footnote in audio history in the
face of the brave new world of digital....
Scott D. Smith
Tom Fine wrote:
Speaking of those dbx LPs, I just bought one over the weekend, a
Concord Jazz live at Montreux album. The dbx Disc decode option in my
dbx II unit works great, plugged the phono preamp right into the unit.
It sounded better than some dbx II encoded tapes I've got -- less
pumping and more natural overall sound. LP surface is in great shape
so I can't tell what ticks and pops would do to the scheme.
If anyone has any of these dbx LPs they'd like to part with or want a
freebie transfer, ping me off-list. It's too bad this didn't catch on
because it's a no-brainer use of the technology. I suppose the biggest
drawback would be that LP levels were never really standardized, so it
would be unlikely that everyone using the technology would agree on a
standard level and dbx is sensitive to level. But, if there could have
been some sort of rigorous standard, combined with late 70's and 80's
quieter vinyl and better cutting, this could have made for some very
pleasant vinyl.
-- Tom Fine
----- Original Message ----- From: "Richard L. Hess"
<arclists@xxxxxxxxxxxxxxx>
To: <ARSCLIST@xxxxxxxxxxxxxxxx>
Sent: Wednesday, November 29, 2006 8:49 PM
Subject: Re: [ARSCLIST] Dolby S/N Stretcher
Dolby has been a licensed format from the beginning and I don't ever
recall it being used for LP release.
It sounds as if the master tapes were Dolby encoded and perhaps one
channel was NOT decoded properly while the other was.
Dolby A and B were the extant flavours in 1970, if I recall
correctly. If it were a master tape error, it would be Dolby A while
if it was a consumer attempt, it would be Dolby B as was used on
cassettes and on FM broadcasts.
There were dbx-II encoded LPs sold for a while, but that never gained
much traction.
If you find out more, please let me know. Also, if you'd like me to
try decoding one side and see if it makes sense, we can exchange some
files (details offline).
Cheers,
Richard
At 08:34 PM 2006-11-29, David Lewis wrote:
I had a strange experience transferring a OP Vox Candide LP to CD
for a friend. The master tape of this album was recorded in Japan
ca. 1970; this was a US pressing. It appeared that one channel was
**significantly** louder that the other. I wanted to adjust for it,
but decided it best in the end not to monkey with the signal.
Vox LPs of this vintage boast something called a "Dolby S/N
Stretcher." I'm assuming that the S/N stands for "Signal to Noise."
Does anyone here know something about this device, how Vox may have
used it, and where it was used in the chain?
It was weird. It could have originated with the Japanese source
recording, or just be the result of a bad mixdown or mastering job.
But it would be useful to know is this effect relates in some way
globally to stereo Vox LPs.
Dave Lewis
Richard L. Hess email: richard@xxxxxxxxxxxxxxx
Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX
Detailed contact information:
http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes.