Film-Tech Forum ARCHIVE: CP-200 Non sync surround decoding thru CAT 150 matrix...

This is topic CP-200 Non sync surround decoding thru CAT 150 matrix... in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Tony Bandiera Jr (Member # 2365) on 09-10-2004, 01:34 AM:

Would like to know if anyone has the modification info needed to make the non-sync formats (60, 61, etc.) actually pass thru the CAT 150 and CAT 560 subwoof cards. The links on the backplane simply route the left and right to the center and surround without any true decoding. My 200 does double duty for film and my video sources.

Any help would be greatly appreciated!!

Posted by Steve Guttag (Member # 268) on 09-10-2004, 06:34 AM:

You will need to come in on one of the "Mag" input lines. If you have an MPU and only 2 or less magnetic capable projectors, then "Mag B" should be available.

Wire your "Pro Logic" sources to the Mag B input Left and Right. You will then need to program an appropriate format on a Cat 153. The format will essentially follow the same as the format 05 logic except you will be selecting ONE of the mag lines (I cant remember if, and here is the confusing part, if it is MAG A or MAG B logic lines). The logic names MAG A and MAG B are not the same as inputs MAG A or MAG B. The logic lines select a group of options.

Some things to consider...the MAG inputs have a fixed input sensitivity of either 100mV or 1V so you may need to pad things.

Steve

Posted by Tony Bandiera Jr (Member # 2365) on 09-11-2004, 01:04 PM:

Thanks Steve! That's an excellent idea. I will be needing an external source selector for the video stuff though. I'll program it and give it a try. [thumbsup]

I'm wondering if this is the same method Edwards theatres was using? I haven't been able to reach thier tech lately.....

And did Dolby ever issue a tech bulletin for this situation? (Sam Chavez, are you out there?)Dolby's website only covers their current line...

Posted by Gordon McLeod (Member # 33) on 09-12-2004, 06:53 PM:

Also a Jumper will be needed to maintain magb as valid for both projectors as mag b is the mag projector input from projector 2 if the changeover is done in the cp200

Posted by Tony Bandiera Jr (Member # 2365) on 10-23-2004, 03:41 AM:

Thanks for the suggestions. [beer]

Upon digging further, and looking at my old block diagram for the signal path, I may have found a way to let the non-sync formats handle the switching duty and do what I need....it'll basically be sending the signal of Lt/Rt from the non-sync switch card thru the BS1 terms 6&7 as if I was adding an SRA-5 to the system. It will involve cutting the traces from SK3 (Where the CAT 143N/Sync card lives)to prevent the signal from taking the normal path...since I do the card swap of the 280T's for SR, won't need the SRA-5 capability.

I'll be trying this setup in the next week or so and will post the outcome!

Edit: In case anyone was wondering, I started this thread before I recovered my original paper copy of the CP-200 manual, which includes some things the online version doesn't....

Posted by Steve Guttag (Member # 268) on 10-23-2004, 05:41 AM:

Hold on up there with that exacto knife son....

Any solution that involves cutting traces on the back of the CP200 processor or control unit backplane is almost always a stupid move.

If your plan is to have the output of the Cat 143 feed the Matrix decoder, then you have a switching problem.

The way the SRA-5 circuit works is that the Left and Right channels are routed through the SRA-5 for ALL formats except Non-Sync. The SRA-5 is now responsible for passing through the signal or applying SR noise reduction to the signal. If a theatre equipped with an SRA-5 were to have the SRA-5 unplugged, only Non-Sync would have left and right.

Part of the installation of the SRA-5 is to change the links on the "Special 1" card. The normal inputs on "P" and "M" are disconnected and the outputs on "13" and "11" are connected to "s" and "15", respectively. Special 1 is just a link card, not a switch card (there is nothing active on it).

So if your plan was to just connect the output pins of the Non-Sync card to the Special 1 card....BZZZZT that won't work well. Your optical sound will still be hot even in Non-sync mode and both Non-Sync and Optical will see each other's low impedance load.

Now you can tack wires from the output of the Non-Sync card to the Mag B inputs and adjust the levels on the card as needed. Again, you will need to program your format with diodes and provide for switching the mag input card (involves removing the suitcase link from the 2-prog/4-proj selector on the back and tacking your control line from JM23 or JM25 to the middle pin in the triangle.

If you are even more cleaver, you can modify the Cat 201 such that the input sensitivity is 300mV for "Mag B" by removing the sensitivity headers associated with Mag B and stuffing appropriate resistors to create a 300mV input (note, the middle header is half for Mag A and half for Mag B so you will need to replinish the wire links to maintain Mag A's levels.

Steve