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Old September 23rd, 2006, 02:58 AM   #1
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Audio Problem - HD100/HD101 Owners Please Read.

I was having some crackling sounds and an intermitent hiss crop up during shooting. I tried different mics etc, but it still appeared, both live and on tape. I sent my camera back to JVC who said that they couldn't find the fault.

In the meantime, my loan camera has developed the same fault!

When my camera was returned, the crackling was still there, easy to hear on a decent set of headphones or speakers.

Has anyone else had this issue? JVC UK says they know nothing of it but I'm sure I read somewhere that JVC USA were replacing an audio capacitor (or something like that). Does anyone know anything about this?

Thanks for any help!!
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Old September 23rd, 2006, 07:26 AM   #2
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Two cameras, same problem. I would go looking for a dry joint on the XLR plug, or dirty pins or damaged cable. Camera sockets can also become a little grubby if they get a lot of use.

If the cable earth shield or its fastening to its connector is damaged, maybe it is intermittently making contact causing crackles without the signal level being affected.

Is there some intermittent humming or AC interference coming through as well?

I assume you swapped cables when you swapped mikes?

Are they phantom powered mikes?

Are they "T" powered mikes?

JVC HD100 supplies Phantom power. A "T" powered mike will work fairly badly for a while then expire as crew on a recent project I was involved in discovered.

Better brains than mine will come along in meantime, have a look through the sound recording threads on this site. Such things are a fairly common wear and tear problem in audio work.
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Old September 23rd, 2006, 08:11 AM   #3
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It's got to be the mic.

I had the same problem with the supplied mic. It started hissing and crackling. JVC replaced it with a new one. I don't use the supplied mic often because I have other mics (condenser, lav etc), but I do expect the supplied mic to work.

The hissing/crackel almost ruined a shot that I need to keep. I could barely clean it up with Wavelab to salvage it and, yes, the crack/hiss was apparent in the headphones when it started. It's funny how it started suddenly. I can single out the shot where it started.
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Old September 23rd, 2006, 09:02 AM   #4
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Thanks guys!

Quote:
Originally Posted by Stephen L. Noe
It's got to be the mic.
I've tried 3 mics and 3 cables.

Problem seems slightly quietier with the supplied mic, not sure why. Same issue on both cameras, that's why I think it must be a production fault

Quote:
Originally Posted by Bob Hart

Is there some intermittent humming or AC interference coming through as well?
No, it's a crackle - like a faulty connection but the sound doesn't drop out, it is "on top" of the audio. There is also a hiss that goes on and off above the expected background hiss/noise.

Quote:
Originally Posted by Bob Hart
I assume you swapped cables when you swapped mikes?

Are they phantom powered mikes?

Are they "T" powered mikes?
Different cables.

All mics P 48V so it could be an issue there. All my mics are P48 though so hard to test.

No one else had the problem?
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Old September 23rd, 2006, 09:15 AM   #5
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Quote:
Originally Posted by Mike Marriage
Thanks guys!



I've tried 3 mics and 3 cables.

Problem seems slightly quietier with the supplied mic, not sure why. Same issue on both cameras, that's why I think it must be a production fault



No, it's a crackle - like a faulty connection but the sound doesn't drop out, it is "on top" of the audio. There is also a hiss that goes on and off above the expected background hiss/noise.



Different cables.

All mics P 48V so it could be an issue there. All my mics are P48 though so hard to test.

No one else had the problem?
Click here for clip with bad audio using JVC mic (WMV). It was very apparent when the audio went bad. When I switched over to the senn mic it was fixed. The senn mic was not phantom 48, instead it was on the mic input. Since then I've connected to the camera using AKG condenser and the audio was flawless on phantom 48.

For me, it was the mic. Check the clip and see if your audio sounds similar to what I had.

S.Noe
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Old September 23rd, 2006, 11:28 AM   #6
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Perhaps you can try a mic that doesn't need phantom power to see if that crackles... or if the problem is only when using phantom power.

Also, is the problem the same on both inputs when the inputs are split?
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Old September 23rd, 2006, 01:48 PM   #7
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Just a random and wild thought. Plug another mike into the spare channel to terminate all connections that are otherwise open circuit on that channel.

If auto-gain is an option on the camera, is the auto-gain on the spare channel selected on and the gain at high sensitivity option? If yes, then select manual and turn the gain selection to low and gain control to minimum. If phantom power is "on" to the vacant chanel, select it "off".

If the spare channel can be isolated by switching or menu, select the spare channel "off".

On the channel being used, hold the release latch in, then slide a XLR plug in and out a few times to remove and possible resistive buildup on any of the pins and earth bond.

My guess is that you have already done all those permutations and still have a fault however nothing said nothing gained.

One last one. The socket on the camera into which the XLR is inserted, is the insuating surface between the pins clean - no dust. Some dust/damp combinations can be conductive enough to cause a hissing which builds to a pop as the current burns off or dries off the conductive path through the damp path and opens the circuit which has built across, then another builds and burns off again with a pop.

With mains power, you will see a carbon track build across insulation between two conductors. While there can be a short across, it is sometimes too resistive to draw enough current to blow a fuse or set off a curcuit breaker but is enough to generate enough pinpoint heat to char the insulation and build fine carbon bridges.

Other than that, it could be an internal fault in the camera, an issue for the repairman.
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Old September 24th, 2006, 11:24 AM   #8
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Thanks again guys!

Quote:
Originally Posted by Stephen L. Noe
Click here for clip with bad audio using JVC mic (WMV). It was very apparent when the audio went bad.
The hiss part of the issue does sound like that, but then there is a crackle as well.

I'll do some more tests to try and narrow down what is causing it.
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Old September 24th, 2006, 11:59 AM   #9
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I've had the same problem. The noise would appear intermittently in the middle of a take, but when I changed the channel the problem disappeared. This happened when running a cos-11 lav with a Lectrosonics unit.
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Old September 25th, 2006, 04:23 AM   #10
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Quote:
Originally Posted by Scott Tebeau
I've had the same problem. The noise would appear intermittently in the middle of a take, but when I changed the channel the problem disappeared. This happened when running a cos-11 lav with a Lectrosonics unit.
Scott if you PM me your email address, I will send you a .wav demoing the issue. We can then see if it is the same problem. I've just been speaking to a JVC engineer who said that I am the first person out of 20,000 users to report the issue, so I want to see if that is true.

I think the problem is due to phantom power - I used an inline P48 module instead of the camera's phantom power and the problem APPEARS to have stopped. It affects both channels. The problem is actually quietier when using the supplied JVC mic. My rode and Senn. mics make the crackling loudier - I'm guessing because they are more sensitive..?
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Old September 25th, 2006, 11:17 AM   #11
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Similar problem

I listened to your audio problem and I've experienced something similar on mine-- kind of wrote it off as a freak thing, as it only happened in one scene.

http://association.aerieproductions.com/Assoc.wmv

Sorry it's a big 111 MB file... but I don't have time to go clip the scene out. The scene in question is near the end, in a wide dolly shot that starts behind a bike wheel and ends on four children sitting at a table. The second half of that shot has the audial wierdness in the highs.
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Old September 25th, 2006, 05:06 PM   #12
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Quote:
Originally Posted by Andrew Wahlquist
Sorry it's a big 111 MB file... but I don't have time to go clip the scene out. The scene in question is near the end, in a wide dolly shot that starts behind a bike wheel and ends on four children sitting at a table. The second half of that shot has the audial wierdness in the highs.
That's sounds like the same problem as me! Is that the only time you had it? Was the mic a high sensitive phantom powered mic? If possible, could you tell me the mic's sensitivity? (It should be a negative dB measurement in the manual.)

Thanks Andrew!
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Old September 27th, 2006, 04:47 PM   #13
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Sennheiser 416

I think we had a Sennheiser MKH416-- but I don't know exactly, since I borrowed it from a guy who owns. You probably could find the sensitivity somewhere online.

I think I had the problem in other spots, but that's the only critical one where it messed up the scene audio. I should try to go through and clean up the audio on that scene when I get a chance.

Speaking of which, Audacity, a freeware audio program has an amazing Noise cleaner. I had a nasty hiss on a recording from an old 80's cassette (like a copy of an original cassette), and it cleaned it right up. You could hear some digital jaggies going on deep in the signal, but man it was pretty surreal. I use Audacity more than I use Adobe Audition.
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Old September 27th, 2006, 06:54 PM   #14
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Thanks Andrew.

I am shooting a music video until Tuesday, luckily MOS. After that the camera is going back to JVC. I'll keep you posted on their findings.
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