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On Camcorder Mic Distortion

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Reave
On Camcorder Mic Distortion
on Nov 5, 2005 at 3:57:21 pm



Hi out there

I recently went to the himalayas and shot video with a PD170 and a senn. 416.
The problem that kept occuring was I was getting distirtion on some of the audio.
Mostly on bus engine sounds and tribal drumming. The thing that puzzles me is
the record levels were fine,well below clipping coming into the camera.I didn't close mic.
I recorded straight into the camera with no outboard pre amp. The rest of the audio
turned out great.It problem seemed intermittent. Would appreciate any suggestions-Thanks-Reave


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Matte
Re: On Camcorder Mic Distortion
on Nov 5, 2005 at 7:19:25 pm

Switch to "Mic Att" (attenuate) position under louder conditions.
Shoot with "auto level" and not Manual audio control.


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Reave
Re: On Camcorder Mic Distortion
on Nov 5, 2005 at 9:16:54 pm


Hi Matt

Just checked camcorder. I have chanels 1 and 2 in linked position also both chanels
AGC (auto gain control) set to off. As I said levels were not going in the red as I was shooting
and they are not showing in red printed to tape. Could having the chanels linked do that?
Had audio level control set to about half way, and readings were hitting about -8. Reave


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Matte
Re: On Camcorder Mic Distortion
on Nov 6, 2005 at 4:30:56 am

[Reave] "Could having the chanels linked do that?"

No.

[Matte] "Switch to "Mic Att" (attenuate) position under louder conditions.
Shoot with "auto level" and not Manual audio control."


Note that I said "auto level" (AGC) should be ON (not off).
That's the better position to reduce overloading the audio with these camcorders.
And, again, the Mic ATT (attenuator) will help a great deal in louder conditions.



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Craig Seeman
Re: On Camcorder Mic Distortion
on Nov 6, 2005 at 10:11:58 pm

AGC in the PD 150/170 actually is more of a limiter so you don't get the pumping you get with other AGC circuits. I always set one channel to AGC and the other OFF. This way one channel will be usable. Which one depends on the circumstances. A "hot" mic can overdrive the input even when the meters don't peak. That's one reason why you need to listen on headphones and not just look at meters.


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Ty Ford
Re: On Camcorder Mic Distortion
on Nov 10, 2005 at 11:56:40 am

That's a very good point. Were you actually watching the meters during the entirety of the problemstic sequences? Were you listening on headphones?

I don't work with shooters who use the PD170 thst frequently, but it is possible that the meters come after a stage that may be overdriven.

On a good day, the headphone circuit will tell you. On a bad day, it may also be placed after the stage that's distorting.

In some rare cases, the mic itself may be overdriven.

Regards,

Ty Ford



Ty Ford's "Audio Bootcamp Field Guide" was written for video people who want better audio. Find out more at http://www.tyford.com


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Stephen Muir
Re: On Camcorder Mic Distortion
on Nov 11, 2005 at 4:34:09 am

It seems unlikely that the distortion would be coming from an overdriven mic, given that the mic in question was a `416. That is, of course, assuming that the mic has not been damaged in some way.

The smaller sony cameras tend to have pretty dodgy mic preamps, which frequently distort on hot mic signals before reaching the gain control (manual or automatic). My reccomendation is to use a small 2-channel ENG mixer with a limiter, bypassing the PD170's preamp altogether and going in line-level. Keep your headphones plugged into that PD170, though.


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Ty Ford
Re: On Camcorder Mic Distortion
on Nov 11, 2005 at 1:31:30 pm

Problem is, too many camcorders today just stick a pad in front of the mic preamp and call it a line input.

There's also some other quirky gear like the Tascam DA-P1 DAT machine tha thass level and peak lights but they are AFTER some stages. You can actually overdrive its input and not light the lights.

In the manual there's something about if you are getting full level with the input set as low as 3, you should insert the pad because you're overdriving one of hte early stages.

OTOH, some folks listen casually, hear audio in the headphones andn think, "OK, audio, fine."

When the shooting starts and some sounds get louder, you may have already taken the headphones off, thinking you're OK.

You are NEVER OK with audio. 90% of the questions I get about problem audio are from people who weren't listening.
Think about doing the same thing with video. You wouldn't stop looking through the viewfinder or at the LCD. Same thing! :)

I know it's difficult to do both audioand video at the same time. If that's where you are, congratulate yourself that your work has brought you to the point where you need to step up your game.

The 4116 has a healthy output, not as high as the AT 4073a, but enough to kick a good signal.

Regards,

Ty Ford


Ty Ford's "Audio Bootcamp Field Guide" was written for video people who want better audio. Find out more at http://www.tyford.com


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