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Old January 22nd, 2004, 10:11 PM   #1
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gl2 audio question

i've noticed that whenever i've used a shotgun mic (senheisser) or a really good lectrosonic wired lav the audio is over modulated (sort of blown out) even though it isn't peaking in lcd's meters. the only way to correct this incomming audio is to use the mic attenuator. is this normal? my camera appears to be highly sensitive to any external mics. please let me know if any one has encountered this situation and whether or not it's a faulty camera or the way the gl2 was designed.
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Old January 22nd, 2004, 10:25 PM   #2
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Michael,
Hmm. What XLR adapter are you using? Could this be a LINE level -vs- MIC level issue?
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Old January 22nd, 2004, 10:35 PM   #3
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i'm using an xlr to mini that i purchased at samys camera, la. it's the the typical xlr/mini that usually go out with all rentals here in la. i don't know much about audio but here is what i found out. the wireless lav receiver was set to +4 fixed (output level). with the attenuator on the audio was ok but somewhat dull sounding. i moved the switch to 30-0 (ouput level) and turned the mic attenuator off. the results were much better sound. does this make any sense?

ps - i'm assuming the 30-0 is actually -30 to 0 output level.
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Old January 22nd, 2004, 11:02 PM   #4
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I moved this thread to this forum to provide it better topical exposure.
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Old January 23rd, 2004, 12:17 AM   #5
 
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Have you shut down the AGC on the cam? When enabled, this will not show distortion/overloading on the meters, but will indeed cause a 'distortion' or muffling of high end if being triggered. Generally this is the first course to take with a DV cam.
AGC is bad. Very bad. It is the auto focus of audio. Should be off, almost always.
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Old January 23rd, 2004, 12:35 AM   #6
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as far as i know the gl2 doesn't have AGC. if it does i haven't found it in any of the menus or the manual.

my audio is set on manual. would AGC be when you set audio on auto?
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Old January 23rd, 2004, 12:48 AM   #7
 
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Yes, AGC is when the audio is set to auto.
Hmmm... You've got the output of your receiver set right, being at -10....and yes, -30--0 is the output range. Although it would be rare, it is possible for a mic to be hotter than a transmitter can be attenuated to manage. I've never seen it, but then again, I've not worked with every system out there.
Everything is set correctly by your post below, and you are still getting blown audio? That seems very odd.
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Old January 23rd, 2004, 12:52 AM   #8
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no, i've been able to correct the audio by setting the output to -30-0 and setting the mic attenuator off. i did several combinations as far as output + mic attenuator on/off and found this to be the best. once again i didn't know what i was doing technically and it was all intuitive (what sounded best to my ear).

does that combination of output (30-0) and mic att off make sense?
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Old January 23rd, 2004, 01:47 AM   #9
 
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Absolutely makes sense.
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Old January 23rd, 2004, 04:41 AM   #10
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With my GL2 and Sennheiser K6/ME66 shotgun mic connected via a XLR->mini cable, the output from the mic does tend to overload the GL2 audio circuit when the GL2's mic attenuator is not activated. With it on I still have to keep the volume knobs turned down quite a ways.

I seem to remember a diagram by Jay Rose (author of "Producing Great Sound for Digital Video" and moderator of the dv.com audio forum) that showed how to wire a cable so that one channel recorded at a normal level while the other was attenuated by 10dB or so, that way when hit by a loud noise if the primary track clips you have the other to fall back to, it just require some work on the computer. I've been meaning to make me one of those cables but haven't yet, and now I can't seem to find the diagram.

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Old January 23rd, 2004, 05:35 AM   #11
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The ME66 and most wireless mics have a rather high output level, on the order of -35 dBV, at standard (1 Pa) sound levels. In loud venues (concerts) the output can be much higher.

If shooting in auto mode, you could have extreme compression with gross distortion (clipping) without the metering hitting the peak.

-35 dBV is the nominal input level rating when using the MIC ATT setting for the MIC input jack. Thus you will probably get better results using the MIC ATT setting under most circumstances, and have a better (lower) noise floor to boot.
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Old January 24th, 2004, 04:40 PM   #12
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cheers douglas n ken (for putting thered here!), this has helped me. I wondered why my standard audio on my xm2 was brilliant sometimes (i was beginning to wonder why people bought expensive mikes!!, but when i filmed a drama sketch lately it was terrible, as there was a glitch every few minutes that sounded like someone pulling out a wire or something. I now think it was because there was a wide variety in the sound levels in the room. I was using auto, so it seems like my camera hasnt displayed the peaks, and just wacked down the recording volume automatically, producing the glitch? I will try manual next time i film something with a quickly changing audio level like drama, where music suddenly blasts or people suddenly shout. When i use my mini disk recorder on auto level this doesnt seem to happen.
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