Film-Tech Forum ARCHIVE: Sound problems from server

This is topic Sound problems from server in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Allan Riddelll (Member # 5090) on 12-05-2015, 07:49 AM:

On checking the first show of the day in the auditorium I noticed that there was loud distortion from all speakers (surround and stage), intermittent and incredibly annoying. On checking amp connections in projection room everything seemed ok. However, on ejecting the feature (Spectre) I found that the
distortion was still present (but not on Non Sync). On switching off the Doremi server, re-booting and starting the film again everything was back to normal and ok. This is a new one on me. Anybody out there have this problem before and possible cause ?

Posted by Mike Blakesley (Member # 26) on 12-05-2015, 09:58 AM:

We had a problem with our Dolby CP650 where the sound was cutting on and off rapidly and the display was flashing on and off -- almost as if it was experiencing rapid random power cuts. Rebooted and everything was fine. I blamed a blip in our electrical supply (common around here). That's the only time the Dolby has ever given us an issue.

I would guess that you had a similar issue since rebooting fixed the problem.

Posted by Marco Giustini (Member # 4544) on 12-05-2015, 10:03 AM:

Make sure you're not running an old version of the firmware which was causing sound distortion.
Make sure you're running the latest version.

Posted by Carsten Kurz (Member # 5396) on 12-05-2015, 10:29 AM:

Which CP? Both previous posters are right, the CP650 may have the 'robosound' bug, and older Dolphin versions had an audio distortion bug as well.

Could be:

---
New Dolphin (DOL12) FW 21.03y

Bug Fixes

Fixed MCore crash leading to Audio noise
For more info please see Dolphin_DCI_1.2_FW_21.2x_ReleaseNotes_001255_v1_6.pdf
---

- Carsten

Posted by Adam Sherwood (Member # 7802) on 12-30-2015, 07:11 AM:

Had similar problemlast week doremi server and barco dp 2k 23b , crackaling noice of the front spekers like to wire's sparking and intermittent sound loss, cp750 was going in and out of its decode mode.. Looks like the problem was to do with the imb block. plugging out the connection from the server tp the cp750 solved it for a short time, then taking out the imb and swapping with another screen so far has fixed the problem the other screen has a dts xd10p sound pro in it , only catch is the serial numbers are wrong so the tms wont like that, the players need to be disconnected, due to swap these back now and see if it comes back seems there was a build up of static and swapping the imb out has grounded the problem

Posted by Dave Macaulay (Member # 813) on 12-30-2015, 08:19 PM:

It's best to use CAT5 STP shielded cable, and to connect the shield to the chassis of the decoder (CP750 for you). The IMB's AES 1-8 and AES 9-16 RJ45 jacks are actually the correct shielded type, but I have not seen any RJ45 to DB25 adapter that has shielded jacks.
We've seen this digital noise problem caused corrupt AC power and high intensity RFI (like using a digital walkie beside the sound rack).

Posted by Ioannis Syrogiannis (Member # 3235) on 01-05-2016, 12:43 AM:

quote: Dave Macaulay
...but I have not seen any RJ45 to DB25 adapter that has shielded jacks.

Correct me if I'm wrong, but the (custom) adapter that comes with the Dolby cat.745 IMB is shielded and has an extra cable to be connected to the chassis of the DB25 for that reason.