Film-Tech Forum ARCHIVE: DA20 with mono reversion

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Posted by Karagir Khush (Member # 1785) on 08-06-2003, 10:35 PM:

Hi to all,

I am about to purchase DA20 with two Cat702 readers for a two projector system. I currently have a mono sound from the

projector solar cells, 6Ch equaliser and a 6Ch volume control.

I want the DA20 to revert to mono analog sound of my processor. So it will be 5.1Ch digital reverting to mono analog.

How do I do it with my processor? I am quite capable of designing the required automation. Can DA20 work with "non-

automation" cinema processors? I have the changeover (motor start signals) all sorted out. The only thing that remains is

reversion. i.e. Format selection and assertion. (Handshaking between my processor and the DA20)

Kindly give me your valued opinions. Please ask if more details from my side are requirde to handle this query.

Regards,

Karagir.

Posted by Darryl Spicer (Member # 711) on 08-07-2003, 12:29 AM:

is this for a personal screening room or a theater. If theater I would chunk the mono system and get a dolby unit or ulta stereo. Better yet cp650 were everything is included.

Posted by Josh Jones (Member # 447) on 08-07-2003, 12:33 AM:

That can be done depending on what default format you wire the processor for. With my CP55 I had to modify the backplane slightly to interface my DA20 with it.

Josh

Posted by Steve Kraus (Member # 476) on 08-07-2003, 01:14 AM:

Can't you just apply your mono audio to pin 20 of J7 on the DA20 and set it to CP200 mode? I don't know for sure this will work because of the logic but if it did it would function as a pass-through when there is no valid digital.

Seems odd that you'd want to have a 6 channel B chain and not be able to play analog stereo. Not to mention how weird this will sound when it reverts and it will revert.

Posted by Michael Brown (Member # 890) on 08-07-2003, 03:20 PM:

When I first read Karagir's post, I was wandering if he meant that he was wanting to downmix the 5.1 SRD to 1 channel. I.e Dolby Digital Mono.

What processor is it anyway?

Posted by Karagir Khush (Member # 1785) on 08-07-2003, 09:07 PM:

However odd it may seem, I have no choice for some time.

I was wondering, if there is any status pin on the DA20 which indicates valid digital data available, which I could make use

of to trigger my own relays for fallback.

If there is any such pin, kindly let me know. Thanks in advance.

Regards,

Karagir

Posted by Steve Kraus (Member # 476) on 08-07-2003, 09:33 PM:

Have you looked at the DA20 manual? If you don't have one it is available on this site in the manuals section in .pdf form.

Posted by Michael Schaffer (Member # 1204) on 08-08-2003, 06:58 AM:

Now I am really curious too why you would have a digital system with apparently working 6 playback channels revert to mono. Will you let us in on the secret?

Posted by Mike Rendall (Member # 1499) on 08-08-2003, 10:03 AM:

There is an automation line in the sense/control feed of the DA20 which (from memory) becomes grounded if in digital, so you need to detect this when it goes O/C and use this line to select the sound format you want.

On the CP65, you just need to bridge a connection on the automation connector from this feed. I think by default it goes to SR (assuming your have SR cards) if you don't there is an option to select A-type.

Without knowing the processor type it is very hard to work out, although from the wiring diagrams you can try to piece it together. I find dts have the best wiring diagrams, I use them whenever I am making up cables for wierd automations.

P.s. - If you are in anyway not competent (no offence) with electronics then I wouldn't suggest fiddling around with your system.

If you let us know the exact setup, i.e. CP type/ brand, other automation, remote faders etc I may be able to help further.

Posted by Peter Hall (Member # 695) on 08-08-2003, 12:49 PM:

I agree with Steve - why go to the hassle of installing external switching as the DA20 has this inbuilt. I assume you are using some sort of stand alone preamp to switch between P1 / P2 and get the cell level to line level. Feed this into the "Audio from CP" 25p female connector on the DA20, hot on pin 20 and cold on pin 1 (or others). I'd guess that your feed from the pre amp is unbalanced, as is the DA20, so I'd suggest feeding this thru an isolating transformer.

If you're using some sort of integrated home cinema amps / equalisers this may be hard to do.

The transfer between 5.1 SRD, 20 to 20 response and tons of headroom and mono, without slit loss eq and NR, would be a little brutal to say the least. I'd stick some eq between the optical and the input of the DA20 to make the most of what you have. Even pinch the eq destined for sub and use this for the optical eq - sort of a really poor mans SR - (if discretes) - the eq would be more effective in this case.

One thought - I think you're going to have to trick the DA20 into going into SRD mode. Sure, the processor can decide which projector to run but it wont bring in the SRD switching until it sees a command from the CP. You could trick this into trying to run Digital by giving the DA20 a momentary earth signal on the Format 10 input of the "CP sense / ctrl" input. You should only have to do this once a day, as nothing (i.e. no format 60 or similar commands) will tell the DA20 not to play Digital.. I do remember something in the DA20 that tells it to give up trying for Digital if it defaults mega times, in which case you may need to give it a further command during the day or reboot..

Posted by Karagir Khush (Member # 1785) on 08-08-2003, 10:56 PM:

Its no secret, but I do need to tell you the story behind it. It is a development I am involved in for the cinema halls in

India, where the concept, the economics, the trade is very different. I will give a detailed account of this in a different

post titled Cinema theatres in India.

Regards,

Karagir.

P.S. I am competant Electronics Engineer so you can throw all the rtechnical stuff you want to. I am going through the DA20 Manuals (thanks to the forum). It is just that I need some confirmation before I finalise my PCB's and do the purchases.

Posted by Karagir Khush (Member # 1785) on 08-11-2003, 08:46 PM:

As Mr. Peter Hall suggested, I will trick the DA20 to believe that CP65 is connected.

With the CP type set to position 2, I will use a key to short pin 12 (GND) to pin 3 (Format 05 Dolby SR) on the DA20 J6

connector. This if I want the show to run in 'auto digital enable' mode.

With CP type set to position 6, I will use a another key to short pin 12 (GND) to pin 5 (Format 10 Dolby SR-D) on the da20

J6 connector. This if I want the show to run in 'auto digital disable' mode.

I understand that the key should be pressed for a period >80ms but < 4 sec. If format 05 key is pressed for > 4sec. DA20

will be forced into Format 05.

I will use an external DPDT switch to energise a DPDT relay to control changeover. One half of the relay will alternately

select the analog sound from the two projectors and the other half alternately connect pin 1 (MS 1) and pin 9 (MS 2) to pin

5 (DGND) of the DA20 J9 conector to effect the changeover.

Can anyone explain me the pin 25 (change over status) on the DA20 J6 connector Does it merely indicate to the CP the status

of MS1 and MS2?

I will keep you all informed on my actual progress. All views invited.

Regards,

Karagir.

Posted by Antonio Marcheselli (Member # 373) on 08-12-2003, 07:18 AM:

I believe that he mean that DA20 reverts to MONO instead of SR when Digital is not available.

Perhaps India's Prints has no SR available??? [Confused]

Bye
A