Info on Dolby 361 and cards?

[Jay Levitt]

As I mentioned in another thread, I'm looking for that now-classic
"Dolby A" sound. The easiest way seems to be to get an actual Dolby
encoder box.

I did some Googling, and here's what I found:

- The effect was usually done with a Dolby 301, and you simply removed
the bass expander card so you only affected (and effected) the mids and
highs. But the 301's are huge and not frequently sold on ebay.

- According to Bruce Breckenfeld, you can modify the "A" card used by
the Dolby 361; you clip R109 and R209, and this disables the bass
expansion. (http://www.ears-chicago.org/eardrum/2000.08.shtml) I
assume he's talking about the cat-22 card.

- The Dolby 363 is a two-channel version of the 361, but it uses
different cards, and I wouldn't know what resistors to clip.

Questions:

- I've also seen Dolby 360s around. How do they differ from the 361?

- All the recent 361s for sale had some sort of built-in Dolby A instead
of a cat-22 card, with what looks to be a blank plate where the card
would go. So I probably couldn't easily perform the modification.
Anyone know anything about these units, what the card is that comes with
them? Or am I misunderstanding the cat-22 card? Photos I've seen on
ebay show a level knob, etc. on the card. For example:


- Does anyone have a schematic for the cat-22 card? Maybe if I could
identify R109 and R209, I could find their equivalent on the SR/A cards
used by the 363 units, which are newer and easier to find.

--
Jay Levitt |
Wellesley, MA | Hi!
Faster: jay at jay dot eff-em | Where are we going?
http://www.jay.fm | Why am I in this handbasket?

[Jay Levitt]

In article >,
says...
> Photos I've seen on
> ebay show a level knob, etc. on the card. For example:

Oops.. accidentally posted without the link. Here's an auction for a
cat-22 card:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=15199&item=
3736015311&rd=1&ssPageName=WDVW

--
Jay Levitt |
Wellesley, MA | Hi!
Faster: jay at jay dot eff-em | Where are we going?
http://www.jay.fm | Why am I in this handbasket?

[Jay Levitt]

In article >,
says...
> Photos I've seen on
> ebay show a level knob, etc. on the card. For example:

Oops.. accidentally posted without the link. Here's an auction for a
cat-22 card:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=15199&item=
3736015311&rd=1&ssPageName=WDVW

--
Jay Levitt |
Wellesley, MA | Hi!
Faster: jay at jay dot eff-em | Where are we going?
http://www.jay.fm | Why am I in this handbasket?

[Predrag Trpkov]

Those modules look like something taken out of a 24 ch. Dolby system and
appear to sport a CAT 22 card in the middle.

Predrag


"Jay Levitt" > wrote in message
...
> In article >,
> says...
> > Photos I've seen on
> > ebay show a level knob, etc. on the card. For example:
>
> Oops.. accidentally posted without the link. Here's an auction for a
> cat-22 card:
>
> http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=15199&item=
> 3736015311&rd=1&ssPageName=WDVW
>
> --
> Jay Levitt |
> Wellesley, MA | Hi!
> Faster: jay at jay dot eff-em | Where are we going?
> http://www.jay.fm | Why am I in this handbasket?

[Predrag Trpkov]

Those modules look like something taken out of a 24 ch. Dolby system and
appear to sport a CAT 22 card in the middle.

Predrag


"Jay Levitt" > wrote in message
...
> In article >,
> says...
> > Photos I've seen on
> > ebay show a level knob, etc. on the card. For example:
>
> Oops.. accidentally posted without the link. Here's an auction for a
> cat-22 card:
>
> http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=15199&item=
> 3736015311&rd=1&ssPageName=WDVW
>
> --
> Jay Levitt |
> Wellesley, MA | Hi!
> Faster: jay at jay dot eff-em | Where are we going?
> http://www.jay.fm | Why am I in this handbasket?

[Predrag Trpkov]

I've been looking for the same info, the one about the mod for the CAT 22
card. Looks like we need the schematics.

The blank plate on a Dolby 361 serves as a protection from dust, I presume.
The CAT 22 module should be hiding safely in the slot behind it. By the way,
I'd like to buy a couple of those blank plates. If anyone has them lying
around please let me know. My 361 units came without any.

They came with a couple of Telcom NR modules instead. Anybody ever used
them, for noise reduction or anything else?

Predrag


"Jay Levitt" > wrote in message
...
> As I mentioned in another thread, I'm looking for that now-classic
> "Dolby A" sound. The easiest way seems to be to get an actual Dolby
> encoder box.
>
> I did some Googling, and here's what I found:
>
> - The effect was usually done with a Dolby 301, and you simply removed
> the bass expander card so you only affected (and effected) the mids and
> highs. But the 301's are huge and not frequently sold on ebay.
>
> - According to Bruce Breckenfeld, you can modify the "A" card used by
> the Dolby 361; you clip R109 and R209, and this disables the bass
> expansion. (http://www.ears-chicago.org/eardrum/2000.08.shtml) I
> assume he's talking about the cat-22 card.
>
> - The Dolby 363 is a two-channel version of the 361, but it uses
> different cards, and I wouldn't know what resistors to clip.
>
> Questions:
>
> - I've also seen Dolby 360s around. How do they differ from the 361?
>
> - All the recent 361s for sale had some sort of built-in Dolby A instead
> of a cat-22 card, with what looks to be a blank plate where the card
> would go. So I probably couldn't easily perform the modification.
> Anyone know anything about these units, what the card is that comes with
> them? Or am I misunderstanding the cat-22 card? Photos I've seen on
> ebay show a level knob, etc. on the card. For example:
>
>
> - Does anyone have a schematic for the cat-22 card? Maybe if I could
> identify R109 and R209, I could find their equivalent on the SR/A cards
> used by the 363 units, which are newer and easier to find.
>
> --
> Jay Levitt |
> Wellesley, MA | Hi!
> Faster: jay at jay dot eff-em | Where are we going?
> http://www.jay.fm | Why am I in this handbasket?

[Predrag Trpkov]

I've been looking for the same info, the one about the mod for the CAT 22
card. Looks like we need the schematics.

The blank plate on a Dolby 361 serves as a protection from dust, I presume.
The CAT 22 module should be hiding safely in the slot behind it. By the way,
I'd like to buy a couple of those blank plates. If anyone has them lying
around please let me know. My 361 units came without any.

They came with a couple of Telcom NR modules instead. Anybody ever used
them, for noise reduction or anything else?

Predrag


"Jay Levitt" > wrote in message
...
> As I mentioned in another thread, I'm looking for that now-classic
> "Dolby A" sound. The easiest way seems to be to get an actual Dolby
> encoder box.
>
> I did some Googling, and here's what I found:
>
> - The effect was usually done with a Dolby 301, and you simply removed
> the bass expander card so you only affected (and effected) the mids and
> highs. But the 301's are huge and not frequently sold on ebay.
>
> - According to Bruce Breckenfeld, you can modify the "A" card used by
> the Dolby 361; you clip R109 and R209, and this disables the bass
> expansion. (http://www.ears-chicago.org/eardrum/2000.08.shtml) I
> assume he's talking about the cat-22 card.
>
> - The Dolby 363 is a two-channel version of the 361, but it uses
> different cards, and I wouldn't know what resistors to clip.
>
> Questions:
>
> - I've also seen Dolby 360s around. How do they differ from the 361?
>
> - All the recent 361s for sale had some sort of built-in Dolby A instead
> of a cat-22 card, with what looks to be a blank plate where the card
> would go. So I probably couldn't easily perform the modification.
> Anyone know anything about these units, what the card is that comes with
> them? Or am I misunderstanding the cat-22 card? Photos I've seen on
> ebay show a level knob, etc. on the card. For example:
>
>
> - Does anyone have a schematic for the cat-22 card? Maybe if I could
> identify R109 and R209, I could find their equivalent on the SR/A cards
> used by the 363 units, which are newer and easier to find.
>
> --
> Jay Levitt |
> Wellesley, MA | Hi!
> Faster: jay at jay dot eff-em | Where are we going?
> http://www.jay.fm | Why am I in this handbasket?

[Scott Dorsey]

Predrag Trpkov > wrote:
>I've been looking for the same info, the one about the mod for the CAT 22
>card. Looks like we need the schematics.

Go to www.film-tech.com and look for the service manual for the Dolby CP-50
cinema sound decoder. I believe that should have a chapter on the CAT 22
card, with docs.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Jay Levitt]

In article >, says...
> Go to www.film-tech.com and look for the service manual for the Dolby CP-50
> cinema sound decoder. I believe that should have a chapter on the CAT 22
> card, with docs.

Sadly, no.. looks like the original manual did, in section 10, but
that's not on the web site, only the block diagram in section 9. We're
getting closer, tho... I looked through a bunch of other CP-* manuals
and didn't see anything either.

--
Jay Levitt |
Wellesley, MA | Hi!
Faster: jay at jay dot eff-em | Where are we going?
http://www.jay.fm | Why am I in this handbasket?

[Scott Dorsey]

In article >,
Jay Levitt > wrote:
>In article >, says...
>> Go to www.film-tech.com and look for the service manual for the Dolby CP-50
>> cinema sound decoder. I believe that should have a chapter on the CAT 22
>> card, with docs.
>
>Sadly, no.. looks like the original manual did, in section 10, but
>that's not on the web site, only the block diagram in section 9. We're
>getting closer, tho... I looked through a bunch of other CP-* manuals
>and didn't see anything either.

I have the original manual, but it's a few hundred miles away at home. I
can probably fax you the schematic if you can wait a week or so.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Jay Levitt]

In article >, says...

> I have the original manual, but it's a few hundred miles away at home. I
> can probably fax you the schematic if you can wait a week or so.

Sure, no hurry.. whenever you get back and get some time. I'll e-mail
you my fax #, and then I can post the doc on my web site for Predrag.

--
Jay Levitt |
Wellesley, MA | Hi!
Faster: jay at jay dot eff-em | Where are we going?
http://www.jay.fm | Why am I in this handbasket?

[David Satz]

Jay Levitt wrote:

> - I've also seen Dolby 360s around. How do they differ from the 361?

The 360 and 361 are both single-channel processors, each designed to hold
one Cat. 22 Dolby "A" card. Later when Dolby SR was introduced, there
were two other cards that could fit this series (one with switchable "A"
and SR and one with just SR). If I'm not mistaken the Cat. 280 was one
of these, but I don't exactly remember which.

The difference between the 360 and the 361 was the switching and connection
arrangement. It's simpler on the 360; the 361 allowed you to connect both
the inputs and outputs of one recorder channel to the same unit and switch
between record (while monitoring the unencoded input) and playback (while
monitoring the decoded output), so it had a few more relays and sockets,
and cost marginally more than the 360.


> - All the recent 361s for sale had some sort of built-in Dolby A instead
> of a cat-22 card, with what looks to be a blank plate where the card
> would go.

?? A 361 should have a front panel cover held in place by two thumb
screws. Behind that cover is a horizontal slot for a Cat. 22 card.

[David Satz]

Predrag Trpkov wrote:

> They came with a couple of Telcom NR modules instead. Anybody ever used
> them, for noise reduction or anything else?

Sure, I used them a fair amount in the mid- to late 1970s. Telcom c4 also
divided the audio spectrum into four bands, but it used a constant 1.5:1
compression ratio in each band for recording, and applied this ratio more
or less regardless of signal level. As a result the net amount of noise
reduction effect was far greater than with Dolby "A". It was a very
effective system but the first series of "C4D" cards (for the Dolby 360
series) was not quite right, and was revised and replaced by Telefunken.

[umbriaco]

in article , Jay Levitt
at wrote on 7/16/04 12:40 AM:

> Questions:
>
> - I've also seen Dolby 360s around. How do they differ from the 361?
Essentially the same. The 360 has only one set of I/O and does not have the
relays that follow record status of the recorder that switch the unit
between encode input to recorder and decode output from recorder.
Both units use the cat 22 for Dolby A and the cat 280 for Dolby SR.
For your application the 360 is a better choice, having less contacts in the
signal path with more straightforward operation.

> - All the recent 361s for sale had some sort of built-in Dolby A instead
> of a cat-22 card, with what looks to be a blank plate where the card
> would go.
That is a cover plate held by 2 knurled screws.
The cat card lives behind that.
Without a cat card, a 360/361 does nothing.

[Predrag Trpkov]

Thanks for your input.

The cards that came with my 361 are Telcom c4 DM. Would they be the revised
ones?

What about the audible artefacts? Greater noise reduction, dbx for example,
doesn't necessarily mean better sound.

Does it mean that there are a lot of masters out there on tapes that are
Telcom-encoded?

Predrag


"David Satz" > wrote in message
om...
> Predrag Trpkov wrote:
>
> > They came with a couple of Telcom NR modules instead. Anybody ever used
> > them, for noise reduction or anything else?
>
> Sure, I used them a fair amount in the mid- to late 1970s. Telcom c4 also
> divided the audio spectrum into four bands, but it used a constant 1.5:1
> compression ratio in each band for recording, and applied this ratio more
> or less regardless of signal level. As a result the net amount of noise
> reduction effect was far greater than with Dolby "A". It was a very
> effective system but the first series of "C4D" cards (for the Dolby 360
> series) was not quite right, and was revised and replaced by Telefunken.

[Pooh Bear]

Jay Levitt wrote:

> - All the recent 361s for sale had some sort of built-in Dolby A instead
> of a cat-22 card, with what looks to be a blank plate where the card
> would go. So I probably couldn't easily perform the modification.
> Anyone know anything about these units, what the card is that comes with
> them? Or am I misunderstanding the cat-22 card? Photos I've seen on
> ebay show a level knob, etc. on the card. For example:

The 361 was simply a box, PSU and I/O that took a Cat 22 card. The Cat 22
card was the 'active' pcb with an edge connector that slotted in and did the
signal processing.

> - Does anyone have a schematic for the cat-22 card? Maybe if I could
> identify R109 and R209, I could find their equivalent on the SR/A cards
> used by the 363 units, which are newer and easier to find.

I believe I do somewhere - I'll look.


Graham

[Pooh Bear]

Predrag Trpkov wrote:

> Those modules look like something taken out of a 24 ch. Dolby system and
> appear to sport a CAT 22 card in the middle.
>

Yup, the Cat 22 is inside the shiny aluminium can.

You need to 'get in and out' of the Cat 22 card and supply power - so these
may not be your best buy.


Graham

[Pooh Bear]

Jay Levitt wrote:

> In article >,
> says...
> > Photos I've seen on
> > ebay show a level knob, etc. on the card. For example:
>
> Oops.. accidentally posted without the link. Here's an auction for a
> cat-22 card:

This is what you need.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=23790&item=3733845111&rd=1&ssPageName=WDVW

Graham

[David Satz]

Predrag Trpkov wrote:

> The cards that came with my 361 are Telcom c4 DM. Would they be the
> revised ones?

The "DM" is an even later series than the ones I have. I believe they
are physically a bit shorter than the older ones but follow the same
specification and circuit behavior.


> What about the audible artefacts? Greater noise reduction, dbx for example,
> doesn't necessarily mean better sound.

There's a minimum dynamic range that the channel requires in order for
systems such as telcom or dbx to work without noise pumping. I once made
a recording of a piano concerto using telcom, where the peak levels on
tape were about 20 dB below 0 VU; there was definite noise pumping in
that recording. But with normal recording levels on ordinary pro-quality
equipment and tape, I never heard any such problems with telcom--and I
definitely, definitely hear them with dbx on some program material even
though some other people (whose hearing I respect) do not.

By "systems such as telcom or dbx" I mean: systems in which the same
degree of compression/expansion occurs at all signal levels throughout
the range, rather than being limited (as in Dolby systems) to a specific
part of the range. In Dolby's noise reduction systems there is always
some recording level beneath which the system goes back to being 1:1,
and that design absolutely prevents noise "breathing" or "pumping" as
long as playback levels have been set correctly to the reference tone.


> Does it mean that there are a lot of masters out there on tapes that are
> Telcom-encoded?

Telcom c4 never achieved the prominence of Dolby "A" anywhere, but it was
used in Germany to some extent, particularly for classical orchestral
recording. A 15 ips 1/4" analog tape using telcom c4 noise reduction
could have nearly the same dynamic range as 16-bit linear PCM. It was
very exciting to have so much dynamic range available in the 1970s.

When I bought my first set of c4d cards from Gotham Audio, I was only the
second customer in the United States; the first was Frank Zappa. (How's
that for an anecdotal reply?)

--best regards

[Predrag Trpkov]

> When I bought my first set of c4d cards from Gotham Audio, I was only the
> second customer in the United States; the first was Frank Zappa. (How's
> that for an anecdotal reply?)

As colorful as it gets. Thanks again.

Predrag

[Phil Brown]

>
>> When I bought my first set of c4d cards from Gotham Audio, I was only
>the
>> second customer in the United States; the first was Frank Zappa. (How's
>> that for an anecdotal reply?)
>
>As colorful as it gets. Thanks again.

Elliot Mazer used them as well
Phil Brown

[Phil Brown]

>Without a cat card, a 360/361 does nothing.

But it doesn't have to be a cat 22. When I was doing TV and movies a cat 43 was
standard everywhere. May still be. Pretty useful.
Phil Brown

[umbriaco]

in article , Phil Brown at
wrote on 7/17/04 8:46 PM:

>> Without a cat card, a 360/361 does nothing.
>
> But it doesn't have to be a cat 22. When I was doing TV and movies a cat 43
> was
> standard everywhere. May still be. Pretty useful.
A cat 43 does nothing without a cat 22.
The cat 43 had a red "card" that docked in the 360/361 unit.
The "card" had a 6 foot cable that went to a little control box with 5
slider controls and a dock for the cat 22.