Film-Tech Forum ARCHIVE: Sound processor

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Posted by Koroye Seitonkumo (Member # 10558) on 04-22-2019, 12:44 PM:

Probably stupid question, but I need to get this out of my chest..

Any way to connect a DCI compliant projector,and server without a sound processor?
Put differently, in the event that a D-cinema doesn't have a sound processor, is there ANYTHING they could do to play movies meanwhile?

Posted by Mike Blakesley (Member # 26) on 04-22-2019, 12:56 PM:

I don't really see how you'd get the sound to the correct amplifiers without some kind of a processor. Cinema projectors don't have sound processors in them, as far as I know.

Posted by Sean McKinnon (Member # 612) on 04-22-2019, 01:01 PM:

If you had an amplifier with balanced AES inputs or a D/A converter you could theoretically just send each channel to its own amp or just the center channel or connect LCR to a mixer and send a sum to an amplifier but it would be less than ideal.

Posted by Carsten Kurz (Member # 5396) on 04-22-2019, 05:57 PM:

DCI servers output multiple AES/EBU signals. They can usually be converted to analog audio by using cheap S/P-DIF converters (+ some basic converter/attentuation cable). There is no guarantee that a simple S/P-DIF DA converter will work with your server, as AES/EBU and S/P-DIF are only closely related, but not 100% compatible. But chances are high you can get away with it.

https://www.gearslutz.com/board/music-computers/962666-aes-ebe-spdif-coaxial-rca-diy.html

https://www.rane.com/note149.html

Your GDC SA-2100 server does not offer XLRs (unless it came with an XLR cable), but the same signals are available for multiple channels on a DB25 connector. You will probably need to make a suitable cable yourself or have a local tech solder it for you.

Typically, you would need two stereo converters to get at least Left/Right and Center (+LFE).

We use a cheap set of S/P-DIF converters together with a simple analog mixer for open air showings. You could also try to dig up a USL DAX 602 oder Doremi AUD-D2A on ebay as a more professional solution. Or a DMA8(+).

- Carsten

Posted by Marcel Birgelen (Member # 6801) on 04-23-2019, 01:54 AM:

The reason why most cinemas put in a sound processor, instead of relying on a lot of loose components that can convert AES/EBU to analog and also do a little-bit of EQ on it is simple:

The average sound processor is a mostly reliable all-in-one package. They do the work of converting analog to digital, but they also apply equalization and general volume control to it. They usually also allow for some input switching, monitoring and relatively straight-forward user interfacing.

There are implementations that use more advanced sound processing, like Q-Sys, that entirely or partly replace the sound processor, but I seldomly see cinemas relying on custom components.

Also, especially, if you go for a refurbished, rather than a new item, the sound processor option (e.g. the CP-650 or CP-750) is probably even less expensive than the "roll your own processor" solution.

Posted by Koroye Seitonkumo (Member # 10558) on 04-23-2019, 05:38 AM:

Thanks alot for.allnthe input. I am looking for a two weeks alternative before i have a proper sound processor installed . I just found a few coloured ports behind my GDC server, 1/8 jacks.. what can they do?

Posted by Carsten Kurz (Member # 5396) on 04-23-2019, 07:12 AM:

I guess these are mainboard audio inputs and outputs as you find them on many standard PCs nowadays. They will not output DCP audio.

What type of audio system do you have currently?

- Carsten

Posted by Koroye Seitonkumo (Member # 10558) on 04-23-2019, 07:44 AM:

I use a neodcp and I have used a stereo 2.1 from a computer using 1/8 jack outputs from the CPU to a stereo inputs on computer..

Posted by Koroye Seitonkumo (Member # 10558) on 04-23-2019, 09:32 AM:

ask if you can install an m-audio delta 1010 8 channel sound card in the server

- also ask if the cable is supposed to come with the server

From my local tech guy

Posted by Steve Moore (Member # 4753) on 04-23-2019, 09:48 AM:

You "could" i guess use one of these at a push

https://cpc.farnell.com/proception/prodac22/digital-to-analogue-convertor/dp/AV27502

I have used this, before to extract VI from the pair of channels 7&8 from the doremi AES output (using a short length of cable from the 25 way D to the phono in, using resistors to pull down the level to SP/DIF ) as the posts above suggest, so there is no reason why 3 of these would not work for L+R, C+LFE, SL+SR and then feed it into a domestic AV amp, assuming it has a 6 channel input.

I certainly wouldn't recommend for any long term use, as I can't comment on long term reliability or if they work all the time. They appear to work as a faux fix for the VI track into a headphone amp.

Posted by Koroye Seitonkumo (Member # 10558) on 04-23-2019, 10:06 AM:

this is what i wanted to do. The problem is that the output is not 25way D. it is 26 way D. Talk to the guy and ask him if he has a pinout for the 26way Dsub connector

His response

Posted by Carsten Kurz (Member # 5396) on 04-23-2019, 10:22 AM:

Look at the server and count the pins yourself I'd say...
It may just be a typo in the data sheet. There is a HD26 connector, though (similiar to VGA style HD15), and Odyssey used to have a HD26 to D25 converter dongle for GDC servers.
I suggest you mail GDC for the pinout. No, typically, you don't get a cable with the server, as there is no standard connector and wiring for the other end of the cable.

You can not install anything in or on that server, it is not a general purpose computer. Don't let your tech mess with it. It is very different from a standard PC running NeoDCP.

If you played stereo so far, you need at least a 4 channel / twin stereo digital/analog converter to play Left/Center/Right. Plus a simple mixer to mix center into both L and R. Better use a dedicated speaker for center.

The cheap DAC type Steve linked to above work on our Sony and Barco server.

http://www.odyssey-products.com/resources/Tech-Resources/DB25-Digital-Audio-Pinouts-(2019).pdf

- Carsten