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Old February 8th, 2010, 11:31 PM   #1
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Argh - Help with Adobe/Matrox/Mac Ingest

Hey everyone, hopefully someone can point us in the right direction quickly.

We're using a Schoeps mic going into a Grace m101 preamp and then through a Symetrix 528e. We're capturing the audio and video though a Matrox MXO2 balanced XLR input on a Mac using Premiere. Here's the issue...

No matter what we do on the preamp or 528e the signal is being cut at around -9db (but usually around -6db). There is a very clear line at the -12db level when we crank the gain up that shows that anything above it is being compressed. We can see the clipping on the Grase and 528e, but everything is getting cut at -12db when it hits the Mac. We're not sure if it is happening in Premiere, or if it's something to do with the Mac, or if it's the Matrox.

Anyone else ever run into this, or have any suggestions for what we can do to open up the range that the Mac will ingest?
Jon Vincent is offline   Reply With Quote
Old February 9th, 2010, 09:58 AM   #2
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I'm immediately suspect of the MXO2. Haven't used it, a two-minute review of Matrox' product pages doesn't tell me much about audio i/o or relevant settings.

However, step one would be to simplify your signal chain to help isolate the problem. You've got two preamps in the chain - get rid of one for testing purposes. Note that the Symetrix has extensive processing. If the MXO2 will accept mic-level, I'd start there! (but it's probably a line level device)

1) mic -> grace101m -> mxo2

2) if no joy, start looking more carefully at the mxo2 settings. Typically, for this sort of device, any software mixer controls should be up full, 0db. Double check to assure that no pads are switched on.

3) If none of this is helping, set up mic -> sym528 -> mxo2, see any changes?

4) Note that the Sym528e does have a compressor. Is this device known to be good, or, is it new to you? Is there any way you can test it outside of this signal chain? If you could get a test tone going into it, and monitor its output on an mixing board, you could determine very quickly if it is behaving properly or is reducing gain. Note that the output of the Grace should be into the line (not mic) input of the symetrix.

Typically, SW such as premiere isn't going to pad down an incoming signal unless you tell it to.

Sorry I can't tell you "press this button and everything will be fine". Maybe there is such an answer out there. However, the above steps should help you isolate the problem to one of the devices or controlling software.
30 years of pro media production. Vegas user since 1.0. Webcaster since 1997. Freelancer since 2000. College instructor since 2001.
Seth Bloombaum is offline   Reply With Quote
Old February 9th, 2010, 05:14 PM   #3
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Seth, you rock! Thanks for the detailed note and ideas. Totally understand that you can't tell me which button to push to make everything fine. If you had, however, I would have next asked which button to push to get my kids to clean their rooms ;)

So.... We tried bypassing the 528e and going straight to the MXO2. While we were able to eek out a little bit more sound, but it was certainly not a big change. Tried mic>528e>MXO2 as well, still no joy.

We have the compressor on the 528e cranked to turn it into a hard limiter for only the loudest sounds, so I don't think the compression is entering into the picture.

Part of the problem with the design of the MXO2 is that it has no audio leveling control at all. As I have been looking at their board I see that a lot of people are also frustrated with that design flaw. I mean, you shouldn't need one right? Seems like the Matrox should not be doing anything to the levels that are hitting it.

We're going to try bypassing the Matrox next time, and go from the 1/4" on the 528e to the 1/8" input on the Mac. I'll let you know what happens!
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