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AJA LHe Card - Audio Problems / Overmodulation

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chris thompson
AJA LHe Card - Audio Problems / Overmodulation
on Mar 15, 2011 at 11:20:37 pm

Hello Friends,

I'm having a problem with the Analog XLR audio outputs on my AJA LHe Kona card - the audio coming through seems abnormally hot, creating over-modulation & crackling/popping. It sounds consistently bad with all applications. All other functions of the card are working properly.

I've had this card putting out nice audio on my system before, but something has changed for the worse and I can't figure it out.

Things I've tried:
-Zapping p-ram.
-Updating Kona Driver.
-Cleaning the card and refitting into PCI-slot.
-Switching PCI-slots.
-Switching Speakers & running through a mixer.

Anyone have experience with this issue, or other ideas on troubleshooting?
Thanks!

chris thompson
bluemarkfilms.com



System Specs-
AJA Kona LHe card
2x3 GHz Quad-Core Intel Xeon MacPro
6 GB 667 MHz DDR2 FB-DIMM
OSX 10.6.6
AJA ControlPanel 8.1.2


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Chad Tingle
Re: AJA LHe Card - Audio Problems / Overmodulation
on Mar 16, 2011 at 5:11:32 am

[chris thompson] "the audio coming through seems abnormally hot, creating over-modulation & crackling/popping. It sounds consistently bad"

Are you using any mp3 audio in your timeline because I often experience this with my LHI when using mp3's for temp music during rough cuts. Once I receive the mixed aiff's I have no issues. I've also read in these forums that from time to time fcp doesn't like wave files either.

Chad Tingle
Producer/Editor


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chris thompson
Re: AJA LHe Card - Audio Problems / Overmodulation
on Mar 16, 2011 at 5:41:49 am

Chad -

Thanks for the tip. Unfortunately the problem is persistent no matter what is being put through the card. wav, aif, or mp3s in FCP, video clips in quicktime, a disc in dvd player, a podcast in itunes, everything... it's all equally hot & distorted.

It feels like something is goofy with the level of the analog audio signal coming through the XLR's that I can't pinpoint...

ct


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Paul Jay
Re: AJA LHe Card - Audio Problems / Overmodulation
on Mar 16, 2011 at 11:29:15 am

Have you connected it to a phantom powered audio connection?
If yes your connections could be toast.
Call AJA.


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Bob Zelin
Re: AJA LHe Card - Audio Problems / Overmodulation
on Mar 16, 2011 at 3:28:53 pm

you are not explaining how you are monitoring.

Your AJA LHe XLR output is a "hot" +4dBu analog out signal. If you go into a stereo receiver or a set of powered speakers that is expecting to see a -10dBu signal, you will get distortion and overmodulation. Are you using a mixer ? If you go into a cheap mixer, you can attenuate (drop the levels) the signal, and you won't get distortion and overmodulation.

However, if you are going into a mixer, are you going into the line inputs, or the MIC inputs. Many inexpensive mixers use the XLR inputs for mic level input only - you need to go into the TRS 1/4" line input.

As for your popping and crackling sound - go to the AJA Control panel, and look to see where your reference is set to. Make sure you are in EXT REF or INT free run, because if you are in Video In, you will get all kinds of strage results. These settings are in the Control tab.

Bob Zelin



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chris thompson
Re: AJA LHe Card - Audio Problems / Overmodulation
on Mar 16, 2011 at 4:40:12 pm

Thanks Bob & Paul Jay.

The Reference in the Control Panel is set to FreeRun.

I have tried monitoring a few ways:

1. LHe into Mackie 1402-VLZ Pro Mixer, Mackie out XLR into Bryston 2BSST-17-SIL-120 amp balanced stereo 1volt XLR inputs, Amp out speaker wire into speakers. Toggling Mic/Line levels, applying trim or limiters on the mixer doesn't help.

2. LHe into Genelec 1029A powered speakers.

Just to eliminate the possibility of Line/Mic level mixups I put the LHe XLRs into a Sony-EX1 camera and jumped back and forth between Mic/Line inputs with headphones on. I'm able to achieve good levels on the camera's meters, but it still sounds like it's coming through a blown speaker.


I did notice a phantom switch on the Mackie - although it was off - I'm wondering if Paul Jay might be onto something? I'll re-post if I learn anything...


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Bob Zelin
Re: AJA LHe Card - Audio Problems / Overmodulation
on Mar 16, 2011 at 7:33:30 pm

The mackie 1402-VLZ XLR inputs are MIC inputs (designed for a -60dBu input), not a line input. The 1/4" TRS (tip ring sleve) stereo phone plug is the line input. Get the correct cable, and go into the 1/4" LINE INPUT on your mixer. If you use the XLR you will get peak distortion on this mixer (and Behringer and Soundcraft mixers).

ALSO, on the Mackie 1204, make sure your TRIM control on the top of the input channel is FULLY COUNTERCLOCKWISE.

Bob Zelin



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chris thompson
Re: AJA LHe Card - Audio Problems / Overmodulation
on Mar 16, 2011 at 8:03:57 pm

Wonderful, Bob. Sounds great now. Thanks for your help.

Now to figure out why I seem to remember using the LHe XLR's out going into the Genelec speakers and it sounding great... (?)

I think I'm losing my mind.


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Bob Zelin
Re: AJA LHe Card - Audio Problems / Overmodulation
on Mar 17, 2011 at 9:07:41 pm

because the Genelec speaker XLR inputs are NOT mic level inputs.
That is why you did not hear distortion.

Bob Zelin



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maurice jansen
Re: AJA LHe Card - Audio Problems / Overmodulation
on Mar 17, 2011 at 10:40:59 pm

hmmm

i'm always a bit surprised that there are
audio mixers (or should i say cigar boxes with XLR's)in a NLE system that cost a 1/10th of the monitors in the end and the system in front.
not even talking about the deck's they are feeding in a worst case scenario.
some systems are so out of balance.
for monitoring ok but in the production chain ????

if i compare to the videochain you see how crazy we do with audio all the time.
its like putting a grade 1 video monitor behind a panasonic MX50mixer
in composite ????
and not understanding why it looks soo fuzzy.

sorry don't want to offend people
but i see this all the time.

meters understanding spec's
helps

People saying they don't make mistake's often make nothing at all!


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