Decklink extreme - distorting audio on XLR output
by Julian Clarke
on
Jan 14, 2006 at 5:46:13 am
Hi,
I've been using the Decklink Extreme on my home edit system succesfully for over a year. A few days ago, we installed a Decklink Extreme at work in a G5. Today, I've been succesfully capturing both audio and video. However, when I play it out, the picture looks great, but the audio is totally clipped, not matter how low the signal is... Now in FCP, the level is fine, and going through the G5s sound ouput the sound is fine. It is only when I go out through the XLR output that the problem happens. The XLRs are going into a mixer, with which I've tried going in through the MIC XLR inputs and also into the Balanced/Unbalanced 1/4 inch inputs. Toggling these setups seemed to sometimes reduced the distortion problem somewhat, but then I'm reduced me to a single channel (don't ask me why, as I have two stereo channels hooked up). I thought maybe the mixer was blown, and brought in my one from home, this produced the same problem.
I'm running the latest version of FCP 5, the latest version of Max OS Tiger, the latest version of the decklink drivers. And I believe it is a G5 Dual 1.8 gigahertz processor.
Re: Decklink extreme - distorting audio on XLR output by Bob Zelin on Jan 15, 2006 at 2:58:38 am
you did not specify what mixer you use, but if you are going into a Mackie, Behringer, Soundcraft Folio, Yamaha, etc. you CANNOT use the XLR inputs, and you must have a properly wired XLR to 1/4" TRS phone plug, to go into the LINE INPUT of your mixer (like a small Mackie mixer), and your TRIM control must be all the way down, otherwise you will get distortion. The XLR inputs of these mixers are mic inputs (-60db inputs), and they cannot be attenuated for a +4dBu signal that comes out of the Blackmagic, or any professional audio device (like a Sony Beta VTR, etc.).
To demonstrate the problem to yourself, stop using the Blackmagic as an audio source, and use your PROFESSIONAL VTR, like a Sony Beta VTR, Panasonic DVCPro VTR, or Sony DV VTR (like DSR45 or DSR1500 - NOT the pro-sumer DSR-11). You will see that these VTR's will distort the XLR inputs of your mixer as well.
Re: Decklink extreme - distorting audio on XLR output by Julian Clarke on Jan 15, 2006 at 11:15:40 pm
Thanks for your help. Yes, I think you are right about the XLR inputs. One of the mixer I was trying was a behringer... can't remember what the other one was. However, when I went through the quarter inch inputs, I still was only receiving 1 channel of audio, so this doesn't expalin why this is happening, does it?
Re: Decklink extreme - distorting audio on XLR output by Trevor Kinsey on Jan 16, 2006 at 1:48:57 am
It sounds to me like you have a faulty component (lead, adaptor or maybe as you first suggested the mixer itself). Do some A/B testing by swapping leads and mixer inputs around until you have checked each component works.
The only other thing to check I guess is that you are sending output to both channels, i.e. are there two (or more) tracks in the timeline, panned to each side, or one track panned to the middle.
Good luck
Trevor Kinsey,
Technical Producer,
CVP Film and Television,
Melbourne,
Australia
