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Old March 23rd, 2004, 06:54 PM   #1
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Audio pros: can you explain this?

Ok I'm going to try and describe this "problem" to the best of my ability. I was testing my UWP-C1 wireless with my new ECM-77 lav mic this afternoon. I was only about the distance my headphones would reach from my camera (as I didn't have an assistant to help test it for me). Anyway I noticed when I turn the attenuation up on the transmitter and try and make the audio louder by tweaking the input levels on my PD-170 I started hearing a weird phenomenon. Everytime I would stop talking abruptly I'd hear an aftershock (in sorts) of hiss. Kinda like the hiss you hear when you have the levels up really high- well it sounded like the hiss would raise and lower as I talked. If I hummed for 3 seconds then stopped for a brief second after I stop I'd hear a louder than normal hiss that quickly lowers. Kinda like the hiss raises anytime the camera recieved an audio signal. After close monitoring I could definitly hear the hiss during my vocals. It seemed like it got louder only when I talked or made a sound.

Is this normal? What causes it? How can I avoid it?


Thanks in advance.
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Old March 23rd, 2004, 07:21 PM   #2
 
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Sounds like you are describing the wonderful world of Automatic Gain Control....AGC. If you can disable it on your camera, kill it. It's not your friend even though the camera manufacturer wants you to love it.
Thye PD 170 is already a little noisy, and the AGC doesn't help. I'm almost sure you can kill it.
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Old March 23rd, 2004, 07:59 PM   #3
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That's a good assumption- it definitly sounds like a problem caused by AGC. However I'm positive it was off because you have to disable it to get manual control on your audio input(s) which I had.
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Old March 23rd, 2004, 08:42 PM   #4
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Hmm, I wonder if the Sony wireless has AGC of some kind of noise compander or compression feature? Does this phenomenon happen with the OEM mic?
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Old March 23rd, 2004, 09:26 PM   #5
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Turn the NR off on the 170. That will solve the problem.
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Old March 23rd, 2004, 09:47 PM   #6
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Mike might be on to something because NR is ON by default. What exactly is it? Noise Reduction right? Why does it cause this? I did explain it correctly right?
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Old March 24th, 2004, 01:22 AM   #7
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I think there is another microphone inside that is used to oppose the camera sounds picked up by the microphone when mounted on the camera. But if it doesn't pick up the sound, then what you hear is the tail-end of the cancellation signal not being opposed. BT,BBBT (Been There, Been Bitten By That)

But that effect went away when I turned it off on my camera. Sony tells you to turn it off in the manual. Drove me nuts because I did an important, and expensive Voice-Over with it on when the camera was new.
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Old March 24th, 2004, 07:56 AM   #8
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"BT,BBBT (Been There, Been Bitten By That)"

LOL! That's a new one I'm going to add to my repertiore.
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Old March 24th, 2004, 10:14 AM   #9
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That's interesting Mike. I wonder why they would have it ON by default and tell you to turn it off in the manual. I wonder if it's the same in the PD-170 manual....I'll have to look for it (remember what section it was in)?

So the hissing "aftershock" following and during vocals is what you heard as well? Just making sure I described it correctly.


Thanks.
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Old March 24th, 2004, 05:03 PM   #10
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It's on by default because it does marvels when you are using the on-camera microphones, whether it be a shotgun like the one supplied or the stereo in-camera kind (I have a PDX10 so I get to have them both).

Stupidly, you can't turn it of for one channel and not the other one so if you are using a lav and want to have the on-camera as a backup or for ambience you have to live without NR.
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Old March 24th, 2004, 06:56 PM   #11
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<<<-- Originally posted by Glen Elliott : That's interesting Mike. I wonder why they would have it ON by default and tell you to turn it off in the manual. I wonder if it's the same in the PD-170 manual....I'll have to look for it (remember what section it was in)?

So the hissing "aftershock" following and during vocals is what you heard as well? Just making sure I described it correctly.


That's it


Thanks. -->>>
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Old March 24th, 2004, 08:27 PM   #12
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Re: Audio pros: can you explain this?

<<<-- Originally posted by Glen Elliott : I was testing my UWP-C1 wireless with my new ECM-77 lav mic -->>>

Is this issue true only when used with the ECM-77 ?
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Old March 24th, 2004, 08:44 PM   #13
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Be sure to follow up on this post Glen.

Personally I don't think it's NR or AGC.

I think it's phase, noise-tails, breathing, fizz... whatever you want to call it. I call it "sizzle".

Some mics bring it out more then others. So far I've had the best luck with trams and an mke2.

In a synthesized UHF wireless set you have a couple things working against you. That frequency selectivity causes some SNR problems that make it necessary to design companding into the circuit. All the technology of convenience creates a compromise between doing one frequency perfectly or a multitude of them with a little sizzle. Sometimes you won't get any sizzle. In my experience the sizzle is hard to predict, but the more sensitive the mic (and larger the diaphragm) the worse the sizzle... but not always. It's a weird thing.

Try to use brand new batteries and check all switches and connections every time. Sometimes a switch may not be quite on and that can add extra noise.

But as far as sizzle I hope the others here are right and I'm wrong, but I doubt it.
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Old March 24th, 2004, 09:40 PM   #14
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UPDATE

Did some more tests tonight and tried turning off the NR- no dice. Still there. It's definitly more noticable on the ECM-77 probably due to the fact it's so sensitive to begin with. I switched to the onboard mic and it was GONE. Sounded fine...so it's definitly something related to the wireless system. I mean it's not too bad- granted, it's more audible on headphones turned all the way up. On the TV is there but can only hear it when I play the audio out through my Bose system.

The aspects that seem to affect it are the mic input level on the camera itself. I get less "sizzle" (or whatever you call it) when I keep the attenuation OFF on the transmitter and bump the input levels on the camera down. Conversly I hear more "sizzle" when I do the opposite. When I turn the attenuation up on the transmitter and crank the mic input on the camera it's MUCH more noticeable.

Do you think it's because of a channel I chose? I don't think it's interference though. Is it something that's inherent of a lower end wireless system?
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Old March 24th, 2004, 11:47 PM   #15
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Glen, noise-tails (as there properly called) are not that uncommon in many wireless systems. As you're discovering you can change settings between the wireless and the cam to help it along.

I would do the most you can with settings and then decide whether or not the sizzle is better or worse with another mic. If that particular mic brings out more sizzle then you have another choice about whether to keep that mic or get a different one.

The intention of my post was to put your mind at ease about having some sizzle. I've got two Lectro systems and ocassionaly I'll hear some sizzle. If I hear any I do one of the following:

1) make sure I've got NEW batteries in.
2) make sure the switch is ALL the way on 'cause it comes on before the switch is fully seated in it's detent.
3) check all connections.
4) adjust levels on cam vs. levels on wireless to minimize it.
5) try a different mic if necessary and available.
6) use an xlr if the lav I'm using fits the ta5f/xlr powersupply.

Depending on how critical the vocal is you may not even notice the sizzle in your final product. Of course I don't know exactly what you're hearing, but I'll bet you dollars to donuts that I can email you a clip saying, "Is this the SIZZLEphfffft", and you'll laugh 'cause you'll know that I know what you mean. If I plug an Oktava on my wireless it sounds great, but then if there's a stong sound like pinging a glass with a pen, you hear, "PINGsssff"... or if I get RIGHT on the mic I can force it with words.

I would try all of the above and try not to lose too much sleep over it. You'd have to spend THOUSANDS or else use a big-ass rack-mount unit like they have at concerts to guarantee no sizzle ever.

This has been my experience with mics I've owned... as you see it doesn't seem to follow any logic:

1) tram... minimal sizzle.
2) mke2... minimal sizzle.
3) m58 newsmic... minimal sizzle.
4) sm86... sizzle-mania.
5) nt3... medium sizzle.
6) me66... minimal sizzle.
7) 4073a... medium sizzle.
8) mk012... sizzles my nizzle.
9) nt1000... minimal sizzle.

So there you have it. No real rhyme or reason as far as I can tell. Minimal means little to none... I used to think my Lectros were as perfect as wires, but as soon as I hook up a large diaphragm mic it's obvious that wireless sets remove a good chunk of soul. So unless you're going to get a Zaxcom I'd prepare for the ocassional annoyance.
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