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Old August 22nd, 2010, 09:47 AM   #1
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Buzzing on audio

I had a search but couldn't find a specific thread for this, so here goes.

I shot something today and realised the audio block on the camera (a Sony PDX10) seems to be creating a buzzing sound on the recording. I know it's not the mic or the XLR cable- I've used them on my Z1 with no problems- so I think something's amiss in the XLR block itself. The buzz is more prominent and persistent the higher the level is and occurs on both Ch1 and Ch2.

So, two questions: Are there any DIY remedies to try with the hardware (I'm not overly fussed- I don't use the camera much anymore, but still...)? And what can I do in post to remove the buzz? I'm using FCP, so is there a brew of filters or settings I can mess with to clean this up a bit?

Answers on a postcard, please!
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Old August 22nd, 2010, 10:34 AM   #2
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I would certainly get a good pair of headphones and do a "laboratory experiment" with all the different variables, microphones, cables, etc. Remember to also experiment with powered from battery vs. mains adapter, etc.
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Old August 22nd, 2010, 11:19 AM   #3
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If the PDX10 preamp is anything like the PD150/170 it's pretty noisey. period end of story. There's very little to do at the camera to fix it. Of course running manual audio keeping the levels just right by watching the bars and using good headphones and riding the wheel to be able to change the levels on the fly is a great start. Otherwise in post (I don't use FCP) I've used in no particular order a NR program, parametric EQ, combination of both to reduce or eliminate the noise with my 150/170. During a louder exercise like a wedding reception it's not even an issue but for quiet times like an interview or wedding vows it can be so pick some noise only play with the EQ a bit to find the freq that works best play around find the sweet spot that will lessen the noise without affecting the sound of the voice (don't want them to sound like Mickey Mouse) and go from there.
That should help get you started I hope.
What do I know? I'm just a video-O-grafer.
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Old August 22nd, 2010, 05:38 PM   #4
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if you ran on a AC power supply, that would be the most likely source of evil here. try the same setup on AC power and battery. you generally want to run line level into these cameras as well to bypass the preamps as most camera audio inputs are actually line level internally.

also cables go bad, ect. an after shoot test is in order because... it happens. also you could of picked up EM from a 60hz source nearby - AC mains, power panel, ect. more investigation is required.
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Old August 22nd, 2010, 09:48 PM   #5
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Not sure about these particular cameras, but I think a lot of times the only difference between mic level and line level is that line level gets padded down and then fed through the mic preamps anyhow. Do you think that might be the case here?

By the way, I haven't tried it on buzzing, but have had great luck with Izotope for noise reduction. It worked really well for some A/C rumble I ran into. I've also had very good luck with Sound Soap, but my tool of choice is usually Izotope.
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Old August 23rd, 2010, 09:10 AM   #6
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It could be an AC ground loop or RF getting somewhere into the audio line. RF can come from poor quality dimmers. Was anything running on AC? Did you have any of your gear plugged into two different AC circuits? Ideally you should keep tech power on the same circuit and lights on a separate circuit. Did any of your audio cable cross or run parallel to an AC cable? What kind of mic were you using?

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Old August 23rd, 2010, 09:34 AM   #7
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The audio on the PDX10 was actually very good, so to me a buzz would represent something out of the ordinary.
There are lots of things to check. First, with the camera off, detach the XLR adapter's cable from the special hotshoe. Inspect the multiconnector and then firmly but carefully reseat it into the hotshoe. This was never exactly easy and had to be done just right and with some effort.
I would actuate each of the switches on the XLR adapter several times and leave them in the correct position for your situation.
Is your mic phantom powered? If so I would test your cables and substitute a battery-powered mic to test.
As others have mentioned, substitute everything else in the setup one piece at a time.
I dimly remember that I had a buzz once when connecting video out to an external Sony AC-powered monitor, even when the camera itself was on battery power.
Also test with the LCD screen off and using only the viewfinder.
Set the Audio Noise Reduction in the Menu to OFF. Having it ON introduced strange audio artifacts.
Lastly you can use the camera's stereo mini mic input, either with a mic like a Rode VideoMic or Stereo VideoMic, or an aftermarket XLR adapter or preamp.

Last edited by Jay Massengill; August 23rd, 2010 at 03:26 PM.
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