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Old July 12th, 2005, 06:11 PM   #1
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AT897 and GL2 Combo

I'm not sure I should post this here or in the GL2 forum, but because it deals specifically with audio, I'm putting it here. If it belongs in the GL2 forum, feel free to move it.

For some reason, sound recorded through my AT897 through a XLR to miniplug adaptor does not play back on my GL2's speakers. The sound is recorded onto the tape, because it sounds fine on headphones and on the computer once the footage is imported, but when I play it back on the camera without headphones it is completely silent. This is with a brand new battery in the AT897, 'MIC' set to NORMAL, 'MIC ATT' set to OFF, and 'AUDIO MODE' set to 16bit. Sound recorded on the GL2's built-in mic plays back fine.

The sound recorded by the AT897 seems kind of quiet when 'Audio Rec Level' is set to AUTO, but I'm not sure if that's just because the AT897 line of microphones isn't very sensitive or if it's specific to my microphone. Is the mic defective? Does anyone know why the sound won't play back on the GL2?

Thanks,
James Duffy
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Old July 13th, 2005, 07:57 AM   #2
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A guess is that your XLR to mini-plug cable may be recording the two channels out of phase with each other. When it's mixed to mono on your camera's monitor speaker you get nothing. Even though you can hear it when playing on stereo speakers such as headphones or your computer, this is still a major problem.
Research your cable. It should be wired to properly split one in-phase signal from the balanced XLR connector into the two unbalanced mini input channels.
A further test you can do is capture the footage, then combine the two tracks by selecting the proper settings in your editing software. Does the waveform and audio disappear?
While the AT897 isn't a very sensitive mic, you can improve things with the correct cable if that's what the problem is.
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Old July 13th, 2005, 02:15 PM   #3
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The cable says "Comprehensive EXF Series Premiere Audio Cable [[symbol that looks like a backwards RL]] AWM E208931 STYLE 2791 VW-1 80[[degrees]]C 30V".

I looked on B&H, and this is what I found, although mine looks slightly different than the picture (my XLR end has more black and less silver, and the black casing on my miniplug end is more round than square):
http://www.bhphotovideo.com/bnh/cont...ughType=search
I'm assuming this is the one they sent me, though, as I ordered it over the phone, and the guy on the other end told me this was the cable I needed. There are no technical specifications on the B&H site, and I can't seem to find anything by googling the cable's model number and such. Where should I look to find out the information you listed?

I'm using adobe premiere pro, and I'm not sure how to combine the two audio tracks. Instead (I'm assuming this is achieving the same effect), I created a new project with the master audio as "mono", and imported a stereo clip into it. As you suspected, when monitoring the audio levels, I can see the volume of the clip shoot up when noise should be coming out of it, but the master volume level barely budges and no sound comes out of the speaker. Just to make it scientific, I added a control -- a clip with sound recorded by the built-in microphone, and sound played normally under mono audio. It seems you've found the problem.

Did the guy send me the wrong cable, or is the cable SUPPOSED to be converting the signal from balanced to unbalanced and it's just defective? How can you tell if the cable will convert a balanced signal to an unbalanced one, and which cable do I need to correctly hook up the microphone to the camera?

Thanks for your help.
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Old July 13th, 2005, 02:43 PM   #4
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Wrong cable. It's a common error, even among audio salespeople. That one is designed to carry a stereo signal between devices that happen to be equipped with different connectors. But when connected to the balanced mono mic it applies equal and opposite signals to each channel. Each channel will drive a device, e.g., the two speakers of a headset or two stereo speakers. But when they add in the GL2's mono speaker circuit they cancel. If you move around in relation to speakers playing those tracks you should hear some weird effects as the sound waves of various frequencies (and therefore various wavelengths) cancel in air at some points

Here's the right cable:
http://www.bhphotovideo.com/bnh/cont...ughType=search
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Old July 13th, 2005, 11:53 PM   #5
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Thanks for the link; I went ahead and ordered the correct cable today. The guy on the phone said that I would have the same problem with that cable and what I needed was a transformer, but I trust that it's because he misunderstood my bumbled explanation of the problem, and that you know what you're talking about.

For future reference; how would one be able to tell that the cable I purchased is the wrong one? I would think that the plugs would be all that mattered.
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Old July 14th, 2005, 12:36 AM   #6
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That guy is misinformed about the differences between the two adapters, and in addition is confusing your problem with one that people have with cameras that provide power to mics through their mic jacks.

Although the connectors are the same for both adapters they're wired differently internally. It's easy to see that each connector has three separate electrical contacts. Correspondingly, there are three separate conductors in the cable.

In the adapter you have now each contact in the XLR connector is wired exclusively to one of the segments in the miniplug. You could verify that with a multimeter or continuity tester.

In the one you just ordered, one of the XLR contacts is connected to two of the mini plug segments (the tip and the ring next to it), and the other two XLR contacts are both connected to the remaining miniplug segment (called the sleeve). Also verifiable as above.
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Old July 18th, 2005, 02:47 PM   #7
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The cable just came in the mail today, and I've tried it out. Not only does the recorded sound now play through the GL2's speakers, but the sound going into the camera is MUCH higher quality. I want to thank you for quickly identifying the problem and pointing me to the solution -- without this forum I would have continued to use the wrong cable and never tapped the potential of my AT897 (which I now see how great a mic it is).

Thanks,

-James Duffy
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