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Audio Dropout Error- Can You Identify?

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Michael Cummins
Audio Dropout Error- Can You Identify?
on Apr 22, 2010 at 6:32:31 pm

I posted this in the Canon Cameras forum, but I'm also posting this here in case someone recognizes it as a MixPre or Sennheiser G2 problem.

Okay, so I've been seeing more and more of these audio dropout errors, and I'm not sure if it's an issue with the wireless Sennheisers (G2 kit), the Sound Devices MixPre, the tapestock I'm using (Maxell miniDV ME), or the XH-A1 itself.

I make sure that batteries in the wireless packs are always fully charged when in use. I usually switch them after three hours of use, or when the battery meter gets to 2 bars, whichever comes first. Same thing for the MixPre, changing batteries after about 3 hours. I use over-ear headphones to monitor all sound through the MixPre, and never heard any of these errors.

If anyone has any ideas on what it might be, please let me know.

Here's the actual video clip with one of these errors. You'll notice it dropout twice as Jill says "fully integrated", and the slight bit of audio you hear is from channel 2, Mike's mic:





Here's the waveform in Soundtrack Pro, notice the lack of signal on channel 1: Soundtrack Pro Waveform Image



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Ty Ford
Re: Audio Dropout Error- Can You Identify?
on Apr 23, 2010 at 12:36:02 pm

[Michael Cummins] "Okay, so I've been seeing more and more of these audio dropout errors, and I'm not sure if it's an issue with the wireless Sennheisers (G2 kit), the Sound Devices MixPre, the tapestock I'm using (Maxell miniDV ME), or the XH-A1 itself.

I make sure that batteries in the wireless packs are always fully charged when in use. I usually switch them after three hours of use, or when the battery meter gets to 2 bars, whichever comes first. Same thing for the MixPre, changing batteries after about 3 hours. I use over-ear headphones to monitor all sound through the MixPre, and never heard any of these errors. "


Hello Michael,

It's easy to get distracted while shooting. Are you 100% sure you were listening intently when these problems happened?

You seem to indicate that you're monitoring at the MixPre. Are you listening just to the mixer output or to the headphone return from the camera? If you're not listening to the camera headphone output, you could have cabling issues between the MixPre and the camera,

If you're listening to the camera, the problems aren't on the front end side. That leaves the A/D converter in the camera (presuming you're audio is being recorded to camera) and tape playback.

Regards,

Ty Ford







Want better production audio?: Ty Ford's Audio Bootcamp Field Guide






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Peter Groom
Re: Audio Dropout Error- Can You Identify?
on Apr 23, 2010 at 1:43:20 pm

What Ty says about end of chain monitoring is absolutely right and very important. That aside commenting on the audio problem you have.

To me it doesnt sound so much liek a TX / RX dropout as the audio being ducked rather severely, perhaps as a result of the audio hitting a limiter / electronics ceiling. This could be anywhere in the chain but Id do some est recordings with that mic. Try to make the problem replicate by over modding its input. The G2 might have a sensitivity issue on the mic input. I know ther have attenuation pads in there for this reason. try biting hard into a word, get the problem audible, then back off on the sensitivity and replicate the word at the same volume. Does it re occur.
Failing that, ids there any agc on the camera being used. Cameras usually dip not duck out the audio, but whop knows.
if it is a Tx RX issue with the g2 try a different frequency. I know sometimes they can be interfered with by,a second channel or some other kit in the environemt youre not even aware of.

Let us know

peter



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Michael Cummins
Re: Audio Dropout Error- Can You Identify?
on Apr 26, 2010 at 3:18:15 pm

Honestly, I couldn't remember if at that point I was monitoring from the MixPre or the camera headphone out, since somewhere in those days of shooting I remember thinking "Maybe it's not smart monitoring from here...."

Toward the end of the second shoot, I was definitely hearing audio dropouts in the headphones because I was calling cut in the middle of good takes. So at this point, I'm thinking it's a cabling issue. I'm ordering a pair of new cables for between the MixPre and the camera. Should I bother with new cables for the receiver (mini to XLR)?

The ones I've been using (going into the camera) have been 25' Pro Co Sound EXM25 cables ($40 cables, so they're not cheap). However, since I have the audio bag hanging from the tripod, I really just coil them up and use about 4-6 feet at the most. I don't have any power cables running in line with them, other than a cable for a teleprompter monitor, but I usually run that off the opposite side of the rig.

If the cable powering the prompter's LCD display got too close to the cables, would that cause an issue?


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Ty Ford
Re: Audio Dropout Error- Can You Identify?
on Apr 26, 2010 at 3:59:41 pm

"Honestly, I couldn't remember if at that point I was monitoring from the MixPre or the camera headphone out, since somewhere in those days of shooting I remember thinking "Maybe it's not smart monitoring from here...."

===It's always best to monitor the camera output. Proper audio snakes (which is what that cable is called) have two XLRs and a headphone return. The headphone return plugs into the camera headphone jack and to the audio mixer return input. There's a switch that allows you to hear either the mixer output or the headphone return.

Toward the end of the second shoot, I was definitely hearing audio dropouts in the headphones because I was calling cut in the middle of good takes. So at this point, I'm thinking it's a cabling issue. I'm ordering a pair of new cables for between the MixPre and the camera. Should I bother with new cables for the receiver (mini to XLR)?

===Hard to say if it was a cabling issue at this point. It could be. It sounds like don't have a snake, the investment would be a good one. Here's one of the ones I use.
http://www.turneraudio.com/peterenghm3-18standardquickreleasecamerasnake.as...

The ones I've been using (going into the camera) have been 25' Pro Co Sound EXM25 cables ($40 cables, so they're not cheap). However, since I have the audio bag hanging from the tripod, I really just coil them up and use about 4-6 feet at the most. I don't have any power cables running in line with them, other than a cable for a teleprompter monitor, but I usually run that off the opposite side of the rig.

If the cable powering the prompter's LCD display got too close to the cables, would that cause an issue?"

===I think the disruptions would be more constant. Maybe just something at that specific location.
Cell phones can kill wireless range. When I run into dropout issues, I check to see where the cell phones and blackberries are and get them turned totally off, not standby.

If the problem continues, I'll move the receivers closer to the transmitters and cable from there to the mixer.

Regards,

Ty Ford



Want better production audio?: Ty Ford's Audio Bootcamp Field Guide






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Michael Cummins
Re: Audio Dropout Error- Can You Identify?
on Apr 27, 2010 at 7:26:06 pm

Michael posted: "If the cable powering the prompter's LCD display got too close to the cables, would that cause an issue?"

Ty posted: "I think the disruptions would be more constant. Maybe just something at that specific location. Cell phones can kill wireless range. When I run into dropout issues, I check to see where the cell phones and blackberries are and get them turned totally off, not standby."

That particular facility had a LOT of high-powered electrical equipment in operation and in various stages of testing. We also had a crane overhead carrying 1-5 ton pieces of gear around, and occasionally right over us. Would the EMFs from this possibly cause the dropouts?

We've had about two dozen dropouts from this location, and only one or two from the other locations.


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