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Dolby A question

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Anonymous
February 14, 2005 7:42:55 PM

Archived from groups: rec.audio.pro (More info?)

I recently acquired two 10 inch reels of 1/4 inch Grand Master 456 tape that
was recorded using Dolby A. I would like, after baking these reels to get
rid of the sticky shed condition, transfer the music (pipe organ,of course)
to CD. What can I use to decode the sound ? Do I need a Dolby A rack mount
decoder or some other Dolby NR system that would work. Any help with this
would be much appreciated.

George

More about : dolby question

Anonymous
February 14, 2005 7:56:01 PM

Archived from groups: rec.audio.pro (More info?)

On Mon, 14 Feb 2005 16:42:55 -0800, "geoley" <geoley@covad.net> wrote:

>I recently acquired two 10 inch reels of 1/4 inch Grand Master 456 tape that
>was recorded using Dolby A. I would like, after baking these reels to get
>rid of the sticky shed condition, transfer the music (pipe organ,of course)
>to CD. What can I use to decode the sound ? Do I need a Dolby A rack mount
>decoder or some other Dolby NR system that would work. Any help with this
>would be much appreciated.
>
>George
>


Dollby A encode means you need Dolby A decode.


Rick Ruskin
Lion Dog Music - Seattle WA
http://liondogmusic.com
Anonymous
February 15, 2005 12:01:38 AM

Archived from groups: rec.audio.pro (More info?)

geoley <geoley@covad.net> wrote:
>I recently acquired two 10 inch reels of 1/4 inch Grand Master 456 tape that
>was recorded using Dolby A. I would like, after baking these reels to get
>rid of the sticky shed condition, transfer the music (pipe organ,of course)
>to CD. What can I use to decode the sound ? Do I need a Dolby A rack mount
>decoder or some other Dolby NR system that would work. Any help with this
>would be much appreciated.

You need a Dolby A decoder. There's no way to do it in software yet. You
may be able to rent one, or you might consider farming the job out to someone
with a decoder. The things are frightfully temperamental and so I would be
very suspicious of one picked up on the used market without having it gone over
thoroughly.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Related resources
Anonymous
February 15, 2005 3:59:46 AM

Archived from groups: rec.audio.pro (More info?)

geoley wrote:

> Do I need a Dolby A rack mount decoder

Yes.

--
ha
Anonymous
February 15, 2005 7:52:06 AM

Archived from groups: rec.audio.pro (More info?)

geoley wrote:
> I recently acquired two 10 inch reels of 1/4 inch Grand Master 456
tape that
> was recorded using Dolby A. I would like, after baking these reels to
get
> rid of the sticky shed condition, transfer the music (pipe organ,of
course)
> to CD. What can I use to decode the sound ? Do I need a Dolby A rack
mount
> decoder or some other Dolby NR system that would work. Any help with
this
> would be much appreciated.
>
> George

There is no reason why you should not copy the tapes to cdr before
decoding the Dolby A. As you can easily make backup/safty cdrs without
significant transfer degradation.Idealy you need to use a pro playback
machine that offers the full range of line up adjustment. It is very
important that you copy the Dolby ref and line up tones as without
these decoding will be a very hit and miss affair.
You can then send the CD to any facility with the dolby gear without
risk and the expense of more tape.
The only way to decode the Dolby A is with a Dolby A decoder.

Steve Lane
Anonymous
February 15, 2005 9:33:35 AM

Archived from groups: rec.audio.pro (More info?)

In article <57347$4211458f$43656244$19488@msgid.meganewsservers.com> geoley@covad.net writes:

> I would like, after baking these reels to get
> rid of the sticky shed condition, transfer the music (pipe organ,of course)
> to CD. What can I use to decode the sound ? Do I need a Dolby A rack mount
> decoder or some other Dolby NR system that would work.

Yes, you need a real Dolby A system. There's no software plug-in
substitute. Since this seems like a one-shot deal, you should look at
renting one rather than buying one.

--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
February 15, 2005 12:07:11 PM

Archived from groups: rec.audio.pro (More info?)

<sstevelp@aol.com> wrote in message
news:1108471926.409767.77250@g14g2000cwa.googlegroups.com...
>
> geoley wrote:
>> I recently acquired two 10 inch reels of 1/4 inch Grand Master 456
> tape that
>> was recorded using Dolby A. I would like, after baking these reels to
> get
>> rid of the sticky shed condition, transfer the music (pipe organ,of
> course)
>> to CD. What can I use to decode the sound ? Do I need a Dolby A rack
> mount
>> decoder or some other Dolby NR system that would work. Any help with
> this
>> would be much appreciated.
>>
>> George
>
> There is no reason why you should not copy the tapes to cdr before
> decoding the Dolby A. As you can easily make backup/safty cdrs without
> significant transfer degradation.Idealy you need to use a pro playback
> machine that offers the full range of line up adjustment. It is very
> important that you copy the Dolby ref and line up tones as without
> these decoding will be a very hit and miss affair.
> You can then send the CD to any facility with the dolby gear without
> risk and the expense of more tape.
> The only way to decode the Dolby A is with a Dolby A decoder.
>
> Steve Lane
>

Steve:
Thanks for your suggestion about transferring to CD after baking before
decoding which is what I will wind up doing and again thanks to all who
responded to my question.
There is a little note attached to each reel that states to make sure to
copy "the Dolby wobble tones with NR off".

George

George
Anonymous
February 15, 2005 6:14:20 PM

Archived from groups: rec.audio.pro (More info?)

On 15 Feb 2005 06:33:35 -0500, Mike Rivers <mrivers@d-and-d.com> wrote:
>
> In article <57347$4211458f$43656244$19488@msgid.meganewsservers.com>
geoley@covad.net writes:
>
>> I would like, after baking these reels to get
>> rid of the sticky shed condition, transfer the music (pipe organ,of course)
>> to CD. What can I use to decode the sound ? Do I need a Dolby A rack mount
>> decoder or some other Dolby NR system that would work.
>
> Yes, you need a real Dolby A system. There's no software plug-in
> substitute. Since this seems like a one-shot deal, you should look at
> renting one rather than buying one.
>

That's surprising. Isn't Dolby A an dynamically adaptive filter with a
more-or-less well-defined transfer function?
Anonymous
February 15, 2005 6:14:21 PM

Archived from groups: rec.audio.pro (More info?)

"Charles Krug" wrote ...
> That's surprising. Isn't Dolby A an dynamically adaptive filter with
> a
> more-or-less well-defined transfer function?

But maybe there is no economically-viable market for a software
Dolby decoder. Or maybe Dolby decided to not license such a thing.
Anonymous
February 15, 2005 6:14:21 PM

Archived from groups: rec.audio.pro (More info?)

Charles Krug <cdkrug@worldnet.att.net> wrote:
>On 15 Feb 2005 06:33:35 -0500, Mike Rivers <mrivers@d-and-d.com> wrote:
>>
>> In article <57347$4211458f$43656244$19488@msgid.meganewsservers.com>
>geoley@covad.net writes:
>>
>>> I would like, after baking these reels to get
>>> rid of the sticky shed condition, transfer the music (pipe organ,of course)
>>> to CD. What can I use to decode the sound ? Do I need a Dolby A rack mount
>>> decoder or some other Dolby NR system that would work.
>>
>> Yes, you need a real Dolby A system. There's no software plug-in
>> substitute. Since this seems like a one-shot deal, you should look at
>> renting one rather than buying one.
>
>That's surprising. Isn't Dolby A an dynamically adaptive filter with a
>more-or-less well-defined transfer function?

Yes, and now that the patent has (fairly recently) expired, the threat of
litigation is somewhat reduced as well.

There is at least one person out there who has been modelling Dolby and
dbx decoding systems using Matlab but he's not ready to publish yet or
to make a commercial product. Maybe in a year.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
February 15, 2005 6:20:53 PM

Archived from groups: rec.audio.pro (More info?)

In article <cbc4a$42122c3e$4365634a$25614@msgid.meganewsservers.com> geoley@covad.net writes:

> There is a little note attached to each reel that states to make sure to
> copy "the Dolby wobble tones with NR off".

The Dolby tone is used for setting the playback level to match the
input level of the decoder (as sell as identifying the recording as
one with Dolyb noise reduction). It's recorded without the noise
reduction engaged, of course.



--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
February 15, 2005 6:54:31 PM

Archived from groups: rec.audio.pro (More info?)

>> Dolby A encode means you need Dolby A decode.


Unless you want it to sound like George Michael. (It works!) : )


V
Anonymous
February 15, 2005 6:58:11 PM

Archived from groups: rec.audio.pro (More info?)

On Tue, 15 Feb 2005 07:22:34 -0800, Richard Crowley <rcrowley7@xprt.net>
wrote:
> "Charles Krug" wrote ...
>> That's surprising. Isn't Dolby A an dynamically adaptive filter with
>> a
>> more-or-less well-defined transfer function?
>
> But maybe there is no economically-viable market for a software
> Dolby decoder. Or maybe Dolby decided to not license such a thing.
>

Oh possibly.

I suppose if you have Dolby A tapes, you have the motivation to hire the
codec, but otherwise it's just an odd filter that was popular twenty
years ago.

"You don't use Dubly for heavy metal . . "
Anonymous
February 15, 2005 8:39:49 PM

Archived from groups: rec.audio.pro (More info?)

<sstevelp@aol.com> wrote in message
news:1108471926.409767.77250@g14g2000cwa.googlegroups.com...
>
> geoley wrote:
> > I recently acquired two 10 inch reels of 1/4 inch Grand Master 456
> tape that
> > was recorded using Dolby A. I would like, after baking these reels to
> get
> > rid of the sticky shed condition, transfer the music (pipe organ,of
> course)
> > to CD. What can I use to decode the sound ? Do I need a Dolby A rack
> mount
> > decoder or some other Dolby NR system that would work. Any help with
> this
> > would be much appreciated.
> >
> > George
>
> There is no reason why you should not copy the tapes to cdr before
> decoding the Dolby A. As you can easily make backup/safty cdrs without
> significant transfer degradation.Idealy you need to use a pro playback
> machine that offers the full range of line up adjustment. It is very
> important that you copy the Dolby ref and line up tones as without
> these decoding will be a very hit and miss affair.
> You can then send the CD to any facility with the dolby gear without
> risk and the expense of more tape.


What would happen if the machine on which the tapes were recorded wasn't
aligned properly? Asimuth, for example. Could it be fixed in software?

Predrag
Anonymous
February 15, 2005 8:39:50 PM

Archived from groups: rec.audio.pro (More info?)

Predrag Trpkov <predrag.trpkovNeSpamu@ri.htnet.hr> wrote:
>
>What would happen if the machine on which the tapes were recorded wasn't
>aligned properly? Asimuth, for example. Could it be fixed in software?

No. There _are_ some azimuth-compensating plug-ins, which allow you to
delay one channel with respect to the other and apply an reverse-comb filter
that is coupled to the delay. But the overall effect isn't all that good
and the treble S/N is poor. It's much easier and better just to make sure
the transcription is correct in the first place. And you _can_ make sure
the transcription is good without having a Dolby decoder.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
February 15, 2005 8:39:50 PM

Archived from groups: rec.audio.pro (More info?)

In article <cut8kq$rmn$1@ls219.htnet.hr> predrag.trpkovNeSpamu@ri.htnet.hr writes:

> What would happen if the machine on which the tapes were recorded wasn't
> aligned properly? Asimuth, for example. Could it be fixed in software?

Not as easily as fixing it in hardware. Simply align the playback
machine to match the tape. It'll never get any better than that.

Of course if you take the route that someone suggested of transferring
the tapes to CD, you lose the opportunity to do that after the fact.

--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
February 15, 2005 9:43:40 PM

Archived from groups: rec.audio.pro (More info?)

"Predrag Trpkov" <predrag.trpkovNeSpamu@ri.htnet.hr> wrote in message
news:cut8kq$rmn$1@ls219.htnet.hr...
>
> <sstevelp@aol.com> wrote in message
> news:1108471926.409767.77250@g14g2000cwa.googlegroups.com...
> >
> > geoley wrote:
> > > I recently acquired two 10 inch reels of 1/4 inch Grand Master 456
> > tape that
> > > was recorded using Dolby A. I would like, after baking these reels to
> > get
> > > rid of the sticky shed condition, transfer the music (pipe organ,of
> > course)
> > > to CD. What can I use to decode the sound ? Do I need a Dolby A rack
> > mount
> > > decoder or some other Dolby NR system that would work. Any help with
> > this
> > > would be much appreciated.
> > >
> > > George
> >
> > There is no reason why you should not copy the tapes to cdr before
> > decoding the Dolby A. As you can easily make backup/safty cdrs without
> > significant transfer degradation.Idealy you need to use a pro playback
> > machine that offers the full range of line up adjustment. It is very
> > important that you copy the Dolby ref and line up tones as without
> > these decoding will be a very hit and miss affair.
> > You can then send the CD to any facility with the dolby gear without
> > risk and the expense of more tape.
>
>
> What would happen if the machine on which the tapes were recorded wasn't
> aligned properly? Asimuth, for example. Could it be fixed in software?


Sorry, I meant the machine on which the tapes were played back.

Predrag
Anonymous
February 15, 2005 10:04:37 PM

Archived from groups: rec.audio.pro (More info?)

In article <cutcch$m0$1@ls219.htnet.hr> predrag.trpkovNeSpamu@ri.htnet.hr writes:

> Sorry, I meant the machine on which the tapes were played back.

Either way, if you align the azimuth so that the playback is optimum,
that's the best you can do. And if you don't do that simple little
thing, you aren't doing your job.

--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
February 16, 2005 1:43:17 AM

Archived from groups: rec.audio.pro (More info?)

"Mike Rivers" <mrivers@d-and-d.com> wrote in message
news:znr1108488549k@trad...
>
> In article <cut8kq$rmn$1@ls219.htnet.hr> predrag.trpkovNeSpamu@ri.htnet.hr
writes:
>
> > What would happen if the machine on which the tapes were recorded wasn't
> > aligned properly? Asimuth, for example. Could it be fixed in software?
>
> Not as easily as fixing it in hardware. Simply align the playback
> machine to match the tape. It'll never get any better than that.
>
> Of course if you take the route that someone suggested of transferring
> the tapes to CD, you lose the opportunity to do that after the fact.


Thanks. Yes, that's why I asked. It's tempting to do just that, especially
in a hurry, relying on the notion that "you can do everything in software
nowadays, you know".

Predrag
Anonymous
February 16, 2005 1:43:18 AM

Archived from groups: rec.audio.pro (More info?)

In article <cutqdq$l2l$1@ls219.htnet.hr> predrag.trpkovNeSpamu@ri.htnet.hr writes:

> Thanks. Yes, that's why I asked. It's tempting to do just that, especially
> in a hurry, relying on the notion that "you can do everything in software
> nowadays, you know".

Haste makes waste. Learn the value of charging by the hour, even if
you can't collect.

--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
February 16, 2005 1:47:17 AM

Archived from groups: rec.audio.pro (More info?)

In article <znr1108488549k@trad>, mrivers@d-and-d.com (Mike Rivers)
wrote:

> > What would happen if the machine on which the tapes were recorded wasn't
> > aligned properly? Asimuth, for example. Could it be fixed in software?
>
> Not as easily as fixing it in hardware. Simply align the playback
> machine to match the tape. It'll never get any better than that.
>
> Of course if you take the route that someone suggested of transferring
> the tapes to CD, you lose the opportunity to do that after the fact.

And I have been told by a local tech who knows first hand, you can't
string Dolby-A encoded audio over to CD then decode it; it just doesn't
work right. Apparently you -have- to decode it first.

--
Eric Frampton, keyboards Atlanta, Georgia, USA
http://www.ericframpton.com

(remove the year from the email address above to get my real address)
Anonymous
February 16, 2005 8:05:10 AM

Archived from groups: rec.audio.pro (More info?)

> And I have been told by a local tech who knows first hand,
> you can't string Dolby-A encoded audio over to CD then
> decode it; it just doesn't work right. Apparently you -have-
> to decode it first.

The only semi-rational reason I can think of is that the non-constant group
delay introduced by the filtering in the A/D and D/A conversion screws up the
Dolby A processor's ability to correctly read the signal's average and peak
levels.

Of course, analog tape recorders introduce non-constant group delay because of
HF spacing loss. And the filtering in digital filters can have constant group
delay, if the designer so desires.


This raises another issue...

Remember how people used to say "Dolby dulls the sound"? About 20 years ago,
after buying two Nakamichi NR-200 Dolby B/C processors, I decided to test this.

I hooked up a processor to encode and decode _without_ a tape recorder in the
loop. (This eliminated a number of problems, including the claim that the
dulling was a pyschoacoustic effect produced by suppressing tape hiss.)
Levels -- both encode/decode and input/output -- were carefully matched.

Switching the processor in and out, there was no question that Dolby B slightly
dulled the sound. Wondering whether this was due to some unintentional
misadjustment, I raised the playback level to the decoder by 1dB, then
recalibrated for unity gain. It still dulled the sound. (The same test, with dbx
II, did not dull the sound.) *

Assuming this is a valid observation, I have a theory as to the reason. It has
to do with an error in the design of Dolby B.

The HF boost added by Dolby B necessarily increases the relative peak level of
the signal. In order to keep the increased peaks from saturating the tape, the
encoder includes peak clipping of the side-chain signal.

Now, since the decoder uses a combination of peak and average detection, it
follows that the decoder will see a lower playback level than it would if the
signal weren't clipped. QED.

In case the "error" isn't obvious -- why have the processor do something to the
signal that the recorder is going to do anyway? And if improvements reduce or
eliminate the problem, the NR processor adds asymmetrical processing that cannot
be reversed.


Of course, it just might be that the Dolby circuits are inherently a bit
dull-sounding, and the dbx circuits aren't.


* Arnie will object that these tests were not double-blind, let alone blind. If
he'd care to stop by, I'd be happy to repeat them, at least blind.
Anonymous
February 16, 2005 10:50:02 AM

Archived from groups: rec.audio.pro (More info?)

"Charles Krug" <cdkrug@worldnet.att.net> wrote in message
>
> That's surprising. Isn't Dolby A an dynamically adaptive filter with a
> more-or-less well-defined transfer function?
>

Yes, but not a much so as SR !


geoff
Anonymous
February 16, 2005 10:50:57 AM

Archived from groups: rec.audio.pro (More info?)

"Richard Crowley" <rcrowley7@xprt.net> wrote in message
news:11144ttjv7dnrc0@corp.supernews.com...
> "Charles Krug" wrote ...
>> That's surprising. Isn't Dolby A an dynamically adaptive filter with a
>> more-or-less well-defined transfer function?
>
> But maybe there is no economically-viable market for a software
> Dolby decoder.


There sure is a market !

geoff
Anonymous
February 16, 2005 10:50:58 AM

Archived from groups: rec.audio.pro (More info?)

In article <4212448e$1@clear.net.nz> geoff@nospam-paf.co.nz writes:

> > But maybe there is no economically-viable market for a software
> > Dolby decoder.
>
> There sure is a market !

Sure, but it's a very small one, and one that's going to figure this
should be a $50 plug-in. I'm sure that if Dolby thought they could
make money at it, they'd have had one out long ago. And when it comes
to knowing what'll make money, Dolby isn't wrong often.


--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo
Anonymous
February 16, 2005 10:04:08 PM

Archived from groups: rec.audio.pro (More info?)

"Mike Rivers" <mrivers@d-and-d.com> wrote in message >
> Of course if you take the route that someone suggested of transferring
> the tapes to CD, you lose the opportunity to do that after the fact.

.....b ut you'd be silly not do do it when transcribing, as it's only a
screwdriver-tweak away...


geoff
Anonymous
February 16, 2005 10:05:48 PM

Archived from groups: rec.audio.pro (More info?)

"Predrag Trpkov" <predrag.trpkovNeSpamu@ri.htnet.hr> wrote in
>
> Thanks. Yes, that's why I asked. It's tempting to do just that, especially
> in a hurry, relying on the notion that "you can do everything in software
> nowadays, you know".

You can't play a reel tape in software though, so one may as well do it
properly when one do play it.

geoff
Anonymous
February 16, 2005 10:06:51 PM

Archived from groups: rec.audio.pro (More info?)

"Eric Frampton" <eric2005@ericframpton.com> wrote in message
>
> And I have been told by a local tech who knows first hand, you can't
> string Dolby-A encoded audio over to CD then decode it; it just doesn't
> work right. Apparently you -have- to decode it first.

Can he explain why ?

geoff
Anonymous
February 16, 2005 10:06:52 PM

Archived from groups: rec.audio.pro (More info?)

Geoff Wood wrote:

> "Eric Frampton" <eric2005@ericframpton.com> wrote in message
>
>>And I have been told by a local tech who knows first hand, you can't
>>string Dolby-A encoded audio over to CD then decode it; it just doesn't
>>work right. Apparently you -have- to decode it first.
>
>
> Can he explain why ?

Maybe some of the encode/decode info is above 22k. Can be done at 96k
sampling rate?
Anonymous
February 16, 2005 10:06:52 PM

Archived from groups: rec.audio.pro (More info?)

In article <4212e2f8@clear.net.nz>,
"Geoff Wood" <geoff@nospam-paf.co.nz> wrote:

> "Eric Frampton" <eric2005@ericframpton.com> wrote in message
> >
> > And I have been told by a local tech who knows first hand, you can't
> > string Dolby-A encoded audio over to CD then decode it; it just doesn't
> > work right. Apparently you -have- to decode it first.
>
> Can he explain why ?

At the time, when I asked why, he basically said "just trust me". And I
do, so I did.

I haven't talked to him about it in years, but it'll be a good excuse to
give him a call. He used to be the staff tech at Master Sound here in
Atlanta, so I dare say he worked on his fair share of machines and Dolby
racks...

e

--
Eric Frampton, keyboards Atlanta, Georgia, USA
http://www.ericframpton.com

(remove the year from the email address above to get my real address)
Anonymous
February 16, 2005 10:06:53 PM

Archived from groups: rec.audio.pro (More info?)

In article <37g6eoF59ksenU1@individual.net>,
Joe Sensor <crabcakes@emagic.net> wrote:
>Geoff Wood wrote:
>
>> "Eric Frampton" <eric2005@ericframpton.com> wrote in message
>>
>>>And I have been told by a local tech who knows first hand, you can't
>>>string Dolby-A encoded audio over to CD then decode it; it just doesn't
>>>work right. Apparently you -have- to decode it first.
>>
>>
>> Can he explain why ?
>
>Maybe some of the encode/decode info is above 22k. Can be done at 96k
>sampling rate?

No. Dolby A got used on a lot of machines where the response dropped off
at 18 KC anyway. The real problems are with low frequency aberrations.

If your tape has tones, I don't see any reason why you can't set for playback
with flat tones and transfer through a digital generation and then back to
decoder.

If the tape does NOT have a full tone ladder and only has Dolby tone,
however, you can't adjust the playback de-emphasis EQ properly. If you
don't have the tone ladder, you have to adjust the de-emphasis by ear
to get the lowest level of pumping. This is especially a big deal with
the low-frequency control. This was, unfortunately, the case with a lot
of Dolby tapes. Certainly all the ones I did...
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
February 16, 2005 10:06:53 PM

Archived from groups: rec.audio.pro (More info?)

On Wed, 16 Feb 2005 10:59:02 -0500, Eric Frampton
<eric2005@ericframpton.com> wrote:

>> Can he explain why ?
>
>At the time, when I asked why, he basically said "just trust me". And I
>do, so I did.

Dolby A is just a multiband compander. There are no subsonic
or supersonic control tones and all sidetrack signals must
be derived from the audio tracks. That's why absolute levels
are so critical.

Chris Hornbeck
Anonymous
February 16, 2005 10:06:54 PM

Archived from groups: rec.audio.pro (More info?)

Chris Hornbeck <chrishornbeckremovethis@att.net> wrote:
>On Wed, 16 Feb 2005 10:59:02 -0500, Eric Frampton
><eric2005@ericframpton.com> wrote:
>
>>> Can he explain why ?
>>
>>At the time, when I asked why, he basically said "just trust me". And I
>>do, so I did.
>
>Dolby A is just a multiband compander. There are no subsonic
>or supersonic control tones and all sidetrack signals must
>be derived from the audio tracks. That's why absolute levels
>are so critical.

It also makes flat response critical too. Which means that things that
might screw the response up (like 1980s digital hardware, or tape machines
with de-emphasis problems) are anathema.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
February 17, 2005 2:30:51 AM

Archived from groups: rec.audio.pro (More info?)

"Joe Sensor" <crabcakes@emagic.net> wrote in message
>> Can he explain why ?
>
> Maybe some of the encode/decode info is above 22k.

From tape ?!!

Maybe he doesn't know as much as people believe he does.

geoff
Anonymous
February 17, 2005 2:30:52 AM

Archived from groups: rec.audio.pro (More info?)

Geoff Wood wrote:
> "Joe Sensor" <crabcakes@emagic.net> wrote in message
>
>>>Can he explain why ?
>>
>>Maybe some of the encode/decode info is above 22k.
>
>
> From tape ?!!

Tape reproduction certainly becomes non linear at that point, but that
doesn't mean there is no signal there. I don't know anything about how
Dolby A encoding works, so it was just a guess.

> Maybe he doesn't know as much as people believe he does.

Who do you mean?
Anonymous
February 17, 2005 2:30:52 AM

Archived from groups: rec.audio.pro (More info?)

Geoff Wood wrote:

> "Joe Sensor" wrote in message

> > Maybe some of the encode/decode info is above 22k.

> From tape ?!!

Without commenting on whether or not information above 22 KHz has
anything to do with accurate Dolby A decoding, even my lowly (compared
to an A80 and such) B67 was 3 dB down at 30 KHz for years.

--
ha
Anonymous
February 17, 2005 10:59:57 AM

Archived from groups: rec.audio.pro (More info?)

"Joe Sensor" <crabcakes@emagic.net> wrote in message
>
>> Maybe he doesn't know as much as people believe he does.
>
> Who do you mean?

Some way back in the thread a dude who was evidently credited with
'knowing' was quoted as stating that it couldn't possibly work.

geoff
Anonymous
February 17, 2005 11:03:16 AM

Archived from groups: rec.audio.pro (More info?)

"Mike Rivers" <mrivers@d-and-d.com> wrote in message .
>
> If you record the CD at a conservative level and adjust the playback
> level so the Dolby tone puts the meters on the Dolby unit on the
> calibration line, there's no reason why it wouldn't work just fine.


Or record your CD at full/whatever level, and set your correct level into
the Dobly by (any) other means.

geoff
!