Film-Tech Forum ARCHIVE: Balanced output and Dolby CP650 SRX R515p

This is topic Balanced output and Dolby CP650 SRX R515p in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Ariel Vocal (Member # 6912) on 12-25-2014, 11:24 PM:

Hello! I have a problem with the connection between a processor Dolby CP650 and the SRXR515p Sony projector, this connection is through the unbalanced output of the projector, this connection is giving me problems with the electrical grounding of the building, is that when I turn the lights on the projection room or in an adjacent room or even connect or turn on any electronic device near the projector, the audio signal is interrupted for a short time, lately the unbalanced audio output is continuously atrophying, even reaching leave the room without audio ... which I solve electricity completely removing the projector for a few minutes, I wonder if there is any way to connect the CP650 processor to the balanced output of the projector, as in the rooms that have the CP750 processor does not exhibit this problem that I have connected to the balanced output.

Thank you very much for your help and happy holidays!

PS: sorry for my English

Posted by Marco Giustini (Member # 4544) on 12-26-2014, 05:24 AM:

There are some interface boards from Odyssey which unbalance the signal on the board itself. That way you can use the balanced output out of your 515.

You should check with your installer but the 650-OPTIO-AES-RJ 650-OPTIO-AES-RJ may be one you could use. It has impedance transformers on board.

Posted by Dave Macaulay (Member # 813) on 12-26-2014, 08:02 AM:

Yes, a balun on each signal line is best to connect any balanced input or output to an unbalanced one.
However, the problem with connecting balanced to unbalanced is more commonly noise (hum) or distortion from an impedance mismatch - not the sound dropping out or fading.
This is an analog signal, correct?

Posted by Marco Giustini (Member # 4544) on 12-26-2014, 08:38 AM:

AFAIK the 515 does not have analogue outputs. It features two AES outputs, one balanced and one unbalanced. I guess that if the signal gets very noisy the 650 may drop the AES completely.

Posted by Carsten Kurz (Member # 5396) on 12-26-2014, 09:50 AM:

And the CP650 digital inputs are not too robust as well. How long is the cable run between the 515 and the CP650? An AES transformer board close to the CP650 would probably be the safest solution, as the one Marco linked-to above.

- Carsten

Posted by Ariel Vocal (Member # 6912) on 12-26-2014, 10:40 AM:

Thank you all for your help , I just contact Odyssey to learn more about your cards , Marco you know the price of this card you used ?, the ever ? ... Someone had this problem before? ... The length of cable between the projector and the processor goes from 16ft and 22ft in some rooms , this problem I have two theaters ..

Posted by Marco Giustini (Member # 4544) on 12-26-2014, 11:07 AM:

Just wait Odyssey for the price!
Those lengths shouldn't be an issue with balanced signals

Posted by Steve Guttag (Member # 268) on 12-26-2014, 01:32 PM:

The short answer is...NEVER connect balanced AES3 to unbalanced AES3-id...you have both level and impedance problems. Odyssey's board has the necessary impedance matching transformers to solve the 110-Ohm (AES3, balanced) to 75-Ohm (AES3-id unbalanced). I don't recall if they also attenuate the signal (I believe they do). AES3 runs at closer to 5V whereas AES3-id is around 1V. In any event, I've used the Odyssey board with complete success so I highly recommend it.

There are other products, like those by Canaire but you'll spend more on 3-4 of those in-inline transformers, cables, connectors...etc than just using the Odyssey board.

And yes, the CP650 is more prone to sound defects on the AES input when using the CAT790 board...they are well known and commonly referred to as "Robosound." If encountered, normally a reboot of the sound processor is required.