Film-Tech Forum ARCHIVE: CAT 280 SR cards

This is topic CAT 280 SR cards in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Tom Wienholt (Member # 1510) on 02-21-2003, 08:36 PM:

I have 2 Dolby 360 units which I think are mainly used for recording purposes. The units have two A-type and two CAT280 SR noise reduction cards. Are these CAT280 cards the same as the CAT280T's? I currently have an SRA5 adapter hooked up with a CP55 and the SR cards only say CAT280, not 280T. (they have a sticker that says modified for playback only) So, would the CAT280's from the Dolby 360 work in a Dolby Cinema Processor?

Posted by Josh Jones (Member # 447) on 02-22-2003, 01:11 PM:

Theoretically, Yes, they should work. My guess would be that it is just a different revision of the card. contact Dolby Labs by phone at 415 558 0200. They would be able to answer that for you.

Josh

Posted by Christopher Seo (Member # 7) on 02-22-2003, 04:10 PM:

The only difference between a Cat. 280 and 280T is that a little jumper in the back of the 280T has been cut to make it suitable for cinema processor use. Don't know the number of the jumper, though, or what will happen if you don't cut it....

Posted by Steve Kraus (Member # 476) on 02-22-2003, 05:01 PM:

A Cat.22 card inserted into a cinema processor is automatically in decode mode. A stock Cat.280 on the other hand ends up going into encode mode...in other words making it "more" SR. Cutting the jumper turns it into a Cat.280T and forces it into decode mode. If you do this yourself please be so kind as to affix a label stating "Modified for playback only. Model Cat280T"

I learned this the hard way once during the early days of SR when I borrowed Cat.280's from a recording studio to plug into ye olde CP50.

Posted by Tom Wienholt (Member # 1510) on 02-23-2003, 03:30 AM:

So Cat280's are the same as Cat280T's except the jumper has been cut on the 280T.

Can someone be more specific about where the jumper is on the Cat280 and the proper way to modify it? Thanks.

Posted by Stephen Furley (Member # 1277) on 02-23-2003, 07:34 AM:

What is the difference between these cards, and the Cat. 350 SR cards, used in the CP-65, etc. I believe that they are not compatible, is this correct?

Posted by Steve Kraus (Member # 476) on 02-23-2003, 10:36 AM:

As I recall they're the same only different. I believe the important difference was that they do not require as many supply voltages, but I may be misremembering. And then obviously different connections and compatibility with the Cat.300 SR/A.

One of my favorite Dolby questions (ranking right up there with why 3--not 2, not 4, not 6, NR slots on the CP.100) is why the CP65, as orginally implemented (before the 222 pretend-SR/A card), when not equipped for 70mm) came with a 222 card and two Cat.350's (for 2 channel's of A and two of SR), and switched to Cat.300's (for 4 channels of A and two of SR) in the 70mm version. It would have been cheaper to fit the non-70mm version with two Cat.300's (2 channels of A or SR) and add the 222 card only on the 70mm version. Yes, the audio routing doesn't work that way but it certainly could have been in the original design. I did get answers to all of these things but I don't want to repeat what I was told privately.

Edit: Typo on card number fixed

[ 10-15-2003, 11:44 PM: Message edited by: Steve Kraus ]

Posted by Peter Hall (Member # 695) on 02-23-2003, 02:45 PM:

Steve -

It does seem that there are two channels of redundant A type in a standard CP65SR however I'd hazard a guess that Dolby has the 222SR in mind from the beginning (which is no doubt cheaper than a couple of 350s). All but the very first CP65s can directly take a 222SRA - switching wouldn't have been done with this incorporated if a suitable card hadn't been envisiaged..

Curious about your comments on the CP100 - how come no meter card for the surround ? How do you set levels for mag (am FAR too young (!?) to have ever run these with 70mm however have looked after a couple in "move down" screens with 35 only..)

Interesting to read the CP100 manual again (I know, sad !) - theres a discussion on using the CP100 as a Digital "B" chain - god forbid !

Did you need 3 x external frames to run a CP100 with format 42 ?

Posted by Gordon McLeod (Member # 33) on 02-23-2003, 04:12 PM:

For format 42 one added 1 360 NR frame to hold the NR card for the surround channel and a eq module for the surround
The two EQ cards for Lc and Rc were replaced with bass filter cards
For format 43 the SA5 was invented that held NR cards for the Lc Rc and S and eq cards for P and Q and the switching

Posted by Chris Trainor (Member # 9) on 10-14-2003, 04:42 PM:

Digging this old post up again. [Smile]

Does anyone know exactly which jumper to cut/make on the 280 to modify it for playback only?

Thanks,
--Chris

Posted by Steve Guttag (Member # 268) on 10-14-2003, 11:03 PM:

It will either be a bare wire or one with a white insulator....It is located right next to the "A" designator.

Steve

Posted by Darren Briggs (Member # 1071) on 10-15-2003, 04:48 AM:

Dont some CAT280's have a switch on them? is this a DECODE/ENCODE switch instead of a link you cut.
The switch didnt seem to do anything when I had a couple.

Darren

Posted by Warren Smyth (Member # 1838) on 10-15-2003, 05:48 AM:

Tom

quote:
Can someone be more specific about where the jumper is and proper way to modify it

I asked a similar question on 08-25-2003 (currently page 11) John Hawkinson's reply should help you. Details of it's function is also on the thread.

If you require more detail, there is a short wire running from pin 1. This is the bottom pin (when the card is mounted vertically) in a group of four. This wire connects pin 1, and this pin connects also with R853. On mine, there is a letter D next to the jumper wire on the inner face of the PCB.

Because this jumper wire is next to one of the pins, it is near the edge, so is accessible even though the jumper may be mounted on the inner face of the PCB.

I think the switch relates to the recording mode (encoding) which is disabled when you cut the jumper.

A careful snip did the trick for me and the results are great.

Posted by Chris Trainor (Member # 9) on 10-15-2003, 12:45 PM:

Cool, thanks. Was looking for a good description of the location... I get paranoid when cutting stuff. [Wink]

--Chris