Film-Tech Forum ARCHIVE: Left channel too high using Doremi server, DMA8+ & CP55

This is topic Left channel too high using Doremi server, DMA8+ & CP55 in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Amanda Mundin (Member # 3386) on 12-10-2007, 12:21 PM:

We are running a Doremi server, through a DMA8+, into a CP55 Aux input and the Left channel seems to be too high in comparison to the Centre and Right channels, however the channel balance seems fine when running Dolby SR from film (using an SRA5). I’ve been told that both the Doremi and the DMA8+ output fixed levels, with no adjustment, meaning the balance must be off somewhere else, but I can’t understand why the balance on film is ok but on the Doremi the Left channel is too high. When the LCR levels are set on the CAT242 using a CAT 85 I assume this sets the output of the CP55 for all formats and not just Optical sound?

Posted by Steve Guttag (Member # 268) on 12-10-2007, 01:06 PM:

Most likely, you have an incorrectly made cable from the DMA8+ to the CP55. The DMA8+ uses balanced outputs whereas the previous DMA8 did not. It is imperative that all outputs have their "-" terminal connected to ground on the CP55 "E". If only say the left channel had its - terminal connected to "E" then it would likely be 6dB hoter than the rest.

Steve

Posted by Paul Carey (Member # 2241) on 12-13-2007, 09:32 AM:

Amanda, i'm pretty sure the levels can be adjusted on the server, but you will need "root" access to do so. I would suggest you contact an engineer to get this done for you. If your on the UK DSN im sure some one at AA can sort you out.

If not, then give Doremi a call. The technical team are very helpful.

Good luck.

Paul

Posted by Mark Gulbrandsen (Member # 72) on 12-13-2007, 10:39 AM:

I happen to be in the middle of making up some custom snakes for three DMA-8's today and Steve's point is well taken. I think Amanda should have a tech double check her cable even if it's a factory made cable to be sure it was properly made up or not defective. Its easy to make a wrong connection inside a DB-25!! Tieing all the minus's to ground is very important when going to an unbalanced input!!

Posted by David Zylstra (Member # 4230) on 12-13-2007, 07:15 PM:

I found the same problem in one of our buildings with the DoReMi plugged directly into the DTS-6AD - I found that the cable provided did not line up the ground pins correctly . . . . . the result was L & LS were at the right level and all other channels were 3db too low - I verified this with a few of the DCP test files that contained pink noise. (the cables only had grounds tied on L & LS . . . . . we also had buzz issues at that location due to the wrong cables - I found that the overall cable shield was tied to C - on the DTS).

Posted by Amanda Mundin (Member # 3386) on 12-18-2007, 11:13 AM:

It was wired incorrectly, it was wired as per the original DMA8 manual, all the + connections were made but only the Left - channel was connected to ground, thanks a lot for the help.