Film-Tech Forum ARCHIVE: from a 5.1 sound card to dolby cp650

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Posted by Venkat SIddareddy (Member # 5931) on 11-09-2010, 02:50 AM:

Hello All,
I am Venkat, a digital film enthusiast from India. Recently we started to build a digital projection system for an art house cinema here in India. We are able to deliver good video quality though our system but we are struggling to find a solution for Audio.

What we have is a creative 7.1 audio card in our server. We want to take the output from the server and go through Dolby cp650 to give a 5.1 output. Although we tried building a connector cable using 3 TRS cables at one end and a d-type 25 pin at the other end. We tested in the cinema but the sound levels were very bad. I also have a optical in and out on my sound card.

Can some please suggest the right way to connect the output from 5.1 sound card to Dolby CP650.

Thanking you in anticipation

Venkat

Posted by Dave Macaulay (Member # 813) on 11-14-2010, 10:50 AM:

Well, the best way would be this: server optical SP-DIF output to Dolby DMA8+ to CP650 analog 6 channel input.
Your way should work though.
Assuming the server has some way to control volume, possibly it's just turned down too far. With Windows this is pretty easy, but on many servers running Linux the OS has been stripped to the bone and finding a volume control application gets tricky.
If the sound card outputs are high impedance then the CAT685 D-A card input impedance could be loading them way down. A buffer amplifier may be needed.
Make sure you have the grounds and signals connected properly at the DB25 connector.

Posted by Sam D. Chavez (Member # 1841) on 11-14-2010, 12:52 PM:

The CP650 card is a Cat. No. 790. Cat. No. 685 is for the CP500.

There are provisions for balanced and unbalanced in to the 790. There is also the matter of the cable type if you are using the SPDif input.

Posted by Marin Zorica (Member # 1716) on 11-14-2010, 02:47 PM:

On CP650 6ch external input sound card should work ok, since dolby level is similar to level from sound card.
Did you try to enter menu on CP650 and raise input levels?

Posted by Venkat SIddareddy (Member # 5931) on 11-14-2010, 11:37 PM:

Dear all,
thanks a lot for your inputs.

We donot have dolby dma8+ at our cinema.
To be very precise what I have is a server with the following audio card.
http://hifi-ring.com/uploads/posts/creative_pcie_x-fi_xtreme-audio.jpg

I need to connect this to CP650.
Currently we have built a cable with three TRS cables connecting to a 25pin D-Sub connector and through this 25 pin we are connecting to the CP650 Exterenal Digital Processor.

The format chosen was 11

Can some one please let me know if what I am doing is right?

Or else please guide me in building the right cables.

Thanking you in anticipation

Venkat

Posted by Tony Bandiera Jr (Member # 2365) on 11-14-2010, 11:59 PM:

Venkat, if I am reading this correctly you are trying to send 6 channels of ANALOG audio out from your server to the EXTERNAL input of the CP-650? If so, from the description of using only 3 TRS cables that is your problem.

EACH channel (for a total of six) needs its own TRS cable, with the cables connected as follows:

(Channel:PIN on DB25)

LEFT + : 14
LEFT - : 1
CENTER + : 20
CENTER - : 9
RIGHT + : 17
RIGHT - : 6
L SURR + : 15
L SURR - : 5
R SURR + : 2
R SURR - : 3
SUBWOOF + : 24
SUBWOOF - : 12

EDIT: Looking at the card in your link, it would appear that the shields of your TRS would be the (-) of the signals, in which case be sure to connect the shields to one of the (-) pins I referenced above.

(Otherwise, leave the shields of the TRS cables disconnected at the DB25 end, unless there is hum and noise, if so connect the shields to the SHELL of the DB25 connector.)

If you are using the option card I/O inputs, then as Sam mentioned cable type is critical for error-free performance.

Posted by Michael Voiland (Member # 5386) on 11-15-2010, 01:29 AM:

The problem with those pc cards is that they carry 2 channels per trs plug.
you need to find the pinout for a stereo trs cable used on computers and then figure out which plugs go to which channels. And wire the db 25 correctly. not the perfect solution but it will do.

Posted by Jeremy Weigel (Member # 4208) on 11-15-2010, 02:27 AM:

I bought one of these to connect my sound blaster card to our CP-500. The Sound Blaster cable comes ready for 7.1. Just had to make a custom short patch cable DB25(m) to RCA(f).

Posted by V.V.Tushit Vijay (Member # 5455) on 11-15-2010, 12:39 PM:

Hi,
Actually you can try with Mr Tony decision . And just check the pin connection are given correctly. And try with Some other Sound card to get the better audio out.

http://www.turtlebeach.com/products/sound-cards/riviera.aspx

And check the out put of the audio card matches the processor. Just try adjusting the level to 50% of its out put.

Hope you ill get it good.

Tusith

Posted by Venkat SIddareddy (Member # 5931) on 11-15-2010, 02:11 PM:

Thank you everyone for your kind support. We will be testing our audio in this week. Will let you know the results.

Thanks once again