HD Omni - super weird problem. Any suggestions?

[johnnyv]

OK, here's a good one.

Using an Avid HD Native Thunderbolt box to go from a MacBook Pro to an HD Omni.

So far so good.

Using the Omni's DB25 DA output connector (channels 1 & 2) to send to XMon for monitoring on self powered Genelecs.

So far so good.

OK. Check this out. Open ProTools, create a mono track and put Signal Generator (white noise) on it. Pan the track in center.

PROBLEM: The audio is right heavy.

BUT WAIT: Hit the MONO button on the Icon. Sounds perfectly balanced.

Hmmm.

OK. Let's send out of Channels 3 & 4 on the HD Omni. Everything is fine in mono or stereo.

Kind of puts suspicion on outputs 1 and 2 of the Omni, right?

I've done a factory reset on the Omni but I still get the same results.

Question for those much smarter than me: should I presume that an output calibration on the Omni is the problem? But if I lowered the output of channel 2, wouldn't my summing to MONO make the signal appear left heavy in MONO?

WAIT! An update! We just rented a second Omni and are getting the same results.

Any thoughts would be appreciated. We aren't smart enough to figure this out alone!

[Darryl Ramm]

Since you tried both Omni through the same XMON then that XMON kooks like it is bad (likely bad 1 or 2 *inputs*--since mono works OK). Or maybe a bad cable or connector (one side of the differential signal floating). Your job is to exclude the cable and/or XMON.

First think I would do is swap cables if you have a spare, or connect the current cable to the XMON Stereo input. (BTW that would have been an easier quick test than renting another Omni). Does that work OK? If so then the problem is input 1 and/or 2 on the XMON.

And to confirm that I would grab a multimeter and inject a sine wave signal into the XMON inputs and measure its level before and after the XMON on each of all of it's main input/output pairs.

[johnnyv]

Thank you, Darryl. At this point, we believe that we had a bad snake carrying audio from the output of the Omni. In other words, we swapped the DB25 - XLR cable and all seems good.

But I guess what surprises me is that a cable could lower an output by 2-3 DB. I would have thought that it either passes signal or not. Obviously, I guess I'm wrong on that?

[Darryl Ramm]

Originally Posted by johnnyv

Thank you, Darryl. At this point, we believe that we had a bad snake carrying audio from the output of the Omni. In other words, we swapped the DB25 - XLR cable and all seems good.

But I guess what surprises me is that a cable could lower an output by 2-3 DB. I would have thought that it either passes signal or not. Obviously, I guess I'm wrong on that?

That is a common failure mode--you lose one side of a differential/balanced analog signal and see exactly around such a loss. Simple as a broken wire, grab a multimeter and check the cable, with many cables not hard to repair yourself.

[johnnyv]

Originally Posted by Darryl Ramm

That is a common failure mode--you lose one side of a differential/balanced analog signal and see exactly around such a loss. Simple as a broken wire, grab a multimeter and check the cable, with many cables not hard to repair yourself.

Yes, I think that's exactly what's happened in our case. Thanks for the info!

[Extreme Mixing]

Originally Posted by johnnyv

Yes, I think that's exactly what's happened in our case. Thanks for the info!

It's been a while, but I seem to remember that the xmon has some Surround quirks that make it so you don't plug into it 1 to 1 with Pro Tools. So check the manuals if the cables are not bad. Like I said, it's been a while, but I think input 2 on the xmon may be for the center channel in surround. Hope that helps.

Steve

[Barry Johns]

The Xmon uses 1 & 5 for left and right, not 1 & 2, it's setup for surround.

[Extreme Mixing]

Yes. What Barry said.

[K Roche]

Well it sounds like you got it sorted out .
So this is just in general, the Omni seems to a bit of a history of having either 1 or 2 become bad, or for some reason simply stop working because of some routing quirk. Where you have to reset the Omni
I have had both things happen. I had to send my Omni back to Avid for a new number 2 channel
And about once a year I have to reset it to get either 1 or 2 back online .