Anyone have LCD Door Open Hum on Audio??

T

tonetone

Member
I recently created a thread about Camera Purr being recorded on my DVX100B PAL. With the help and suggestions of everyone here I managed to discover that the camera purr was caused by the LCD door being open while recording audio.

http://www.dvxuser.com/V6/showthread.php?t=88083

I returned the camera to PROAV on Friday Feb 23. They sent it back to Panasonic satisfied there was a fault. Today I got a call saying that Panasonic had sent it back to PROAV stating that there is no fault!!!!!!!!!

Does anyone here have a low hum recorded to tape and can be heard through headphones while monitoring when the LCD door is open? When the LCD door is closed there is no hum through headphones and no hum recorded to tape.

When I posted before no one here said they had this problem. And that I should send it back. The hum is not very loud but it can be heard when the LCD door is open.

I bought this equipment so I can make good quality shorts.

If Panasonic had stated that this hum was a design fault I might have been able to accept it. But since no one else has this problem it seems to be a fault with my camera.

Please help.

PROAV are going to contact Panasonic again. Two and a half weeks I've been without my carmera. I really thought Panasonic would be more on the ball and be able resolve this issue one way or another by now.

Does anyone else have this problem?
 
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Post up some files demonstrating the hum. These files could also be passed along to Panasonic to prove there is an issue.

Cheers
 
Audio Test file uploaded at: http://www.ourmedia.org/node/300413

I've uploaded a mp3 compressed audio file. There is a little harmonic tinny distortion in the vocal because of the compression but it is acceptable to determine the camera purr. The audio test may also be downloaded from that site.

It's taken me ages to find a place to post this audio test. Now that I know where to do it I'll be happy to upload without compression and more files if anyone wants.

Also this might be a handy free site to know about. It's free. And it looks reputable.

One question I would like to ask: Could someone put a tape in their DVX100B, plug in their headphones, open and close the LCD door, can you hear the camera purr when open, nothing when closed?
 
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I'm having the same issue with my new JVC-HD100. LCD screen open has HUM, closed has no hum.
 
Well, I can only listen on headphones right now but I am not hearing a big difference in bg noise between window open and closed. Might be my headphones or the compression. I will try again at home with proper monitors.

You say you are 8 feet away with a dynamic mic? You definately wouldn't be picking up any acoustical noise from the camera in that situation so perhaps the noise you notice is caused by extra rf from the LCD being on. Are you using balanced cables? Does the noise occur if the LCD is on but in it's cradle (turned 180 degrees and closed). Does the noise change depending on where you put the cable?

Cheers
 
I've used 3 different good quality cables and 2 different mics.

I'll happily upload more audio tests if you want with the Oktava Mk-012.

At the moment PROAV or Panasonic have my camera so I can only supply audio tests I did a few weeks ago and uploaded into my NLE.

The Camera Purr is very obvious on other tests but it should be more than audible on the upload I have supplied. If you want more I will happily upload more tests.
 
I seem to recall there was a similar problem with the first PD170s. I think there was a rumor that Sony actually halted the production line until the problem was fixed. Something about a poorly grounded internal cable connecting the LCD.

I remember it because I was planning on buying a PD170 until I heard about this problem. It triggered me to check out the then new DVX100A. Never looked back. :love4:

-Dan
 
tonetone,
I forgot to mention that I did listen to the MP3 file. Like wabbit, I can only hear a very slight variation in the background noise level. I pulled up a frequency spectrum display and there appears to be band of noise in the 300-400 hz range when the door is open. When I really cranked up the db, I could hear it but I don't think I would have ever noticed it while listening at normal levels. Unless something is getting lost in the encoding, your ears are far more sensitive than mine.

-Dan
 
But is this normal?

I know the camera purr is not very loud but it is there when the LCD door is open. When I listen it is like day and night. It's very clear to me.

With the LCD door closed the audio is perfectly clean. Why is this? Do all DVX100B cameras do this?
 
I've posted up some more audio tests:

http://www.ourmedia.org/node/300866

This is a better Dynamic Mic Audio Test to demonstrate the camera purr. The compression ratio is now only 1:4. Below the audio window at My Other Works are the other audio test files.

Has anyone else experienced this CAMERA PURR? Surely this is not acceptable?
 
its quit minor for what i heard in realy bad cameras as pd-170 or few dvxex
the hum is not so big and as wabit sas if you wasnt tell it is there i dont think that i was really hear it .
question - do you hear it better in your headphones as what may happend that the amplification is much graqter in your headphone amp for the humm that really goes to the tape , and the dvx is known one of the worst for its headphone .
also check if you have any change in the hum levels in your headphones when you work e to e on the menu or in tape ( not raly tape but after ato d converter and back .
as iit sims to me and if the compression doesnt makerade it idont see any problem work with that camera .
 
Well Tone I had a chance to listen on good monitors and only when I chopped your voice out to marry the open and closed noise was it obvious. As Dan said you can see the noise in spectral display right around 350hz.

It is probably a poorly shielded wire or connection somewhere inside the camera and I don't think it is "normal" but I sold my DVX over a year ago so can't experiment directly. Perhaps someone else will. Have you tried using an external preamp? As Oleg asked, is this effect more pronounced through your headphones in the camera or is it the same as listening to it later from another source?

It' probably not what you want to hear but if Panasonic can't/won't do anything with it I would learn to live with it. The bg noise is pretty loud already (how high is the gain cranked on those tests?) so the "door" noise just blends in with it. As long as you don't switch between door open and closed within a shot or scene it should be fine.

Sorry if that wasn't what you wanted to hear but the good news is you have some pretty good ears there. :thumbsup:
 
I haven't listened, as I'm stuck on a 56k line right now, but from what others have said (the noise being at ~350Hz), I'd venture a guess as to it being caused by the backlight inverter.
It may well be an electrically noisy board, maybe combined with a loose ground connection somewhere.

Good luck with getting it fixed.
 
Thanks for the replies. In response to the questions:

I don't have a preamp. My audio set-up is really relying on the DVX itself.

The purr is at about the same level through headphones. So to my ears I can hear it the moment I open the LCD door.

How high is the gain cranked? Everything is set to normal. So the audio inputs are at 12 o'clock. On the Levels up-down test I turn the audio levels to 3 o'clock. The purr disappears even when the LCD door is open. But once I turn it back to normal, 12 o'clock, the purr can be heard again.

If it is a poorly shielded wire then hopefully this time Panasonic will sort it. But the main thing is, I find it hard to believe that on such a brilliant camera there would be such an audio problem. As Wabbit says it doesn't sound normal.

Has anyone with a DVX100B tried putting a tape in, put headphones on, opened and closed the LCD door?
 
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Update. I'm posting this so if anyone ever does a search about LCD door hum they'll know what the result of this thread was.

All DVX100B's record hum when the LCD door is open. When it is closed they don't. That's normal according to Panasonic.

Proav sent my DVX100B to Panasonic twice. Panasonic said the noise is within an acceptable range.

It's such a shame that good quality clean audio cannot be recorded using this camera when the LCD door is open. If they bring out a DVX100C then I think this is something they really should address.

So after four and a half weeks I have been reunited with my DVX100B. I'm glad to have it back. For image quality it's great. I'll just have to learn to live with its audio limitations. Shame.

Once again thanks to everyone who replied on this thread.
 
tonetone said:
I recently created a thread about Camera Purr being recorded on my DVX100B PAL. With the help and suggestions of everyone here I managed to discover that the camera purr was caused by the LCD door being open while recording audio.

http://www.dvxuser.com/V6/showthread.php?t=88083

I returned the camera to PROAV on Friday Feb 23. They sent it back to Panasonic satisfied there was a fault. Today I got a call saying that Panasonic had sent it back to PROAV stating that there is no fault!!!!!!!!!

Does anyone here have a low hum recorded to tape and can be heard through headphones while monitoring when the LCD door is open? When the LCD door is closed there is no hum through headphones and no hum recorded to tape.

When I posted before no one here said they had this problem. And that I should send it back. The hum is not very loud but it can be heard when the LCD door is open.

I bought this equipment so I can make good quality shorts.

If Panasonic had stated that this hum was a design fault I might have been able to accept it. But since no one else has this problem it seems to be a fault with my camera.

Please help.

PROAV are going to contact Panasonic again. Two and a half weeks I've been without my carmera. I really thought Panasonic would be more on the ball and be able resolve this issue one way or another by now.

Does anyone else have this problem?
Click to expand...

One of the many reasons I don't use a camera to record audio.

http://www.theultimatewireless.com/deva_v.htm

http://www.sounddevices.com/products/7.htm
 
That's an unfortunate but predictable response from Panasonic (or any large corporation). I think as long as you keep the door opened or closed throughout a scene the noise will just blend into the bg ambient. If you are doing something that will be played in a theatre or other quality sound system you might want to record double system anyways.

Cheers
 
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