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Old January 6th, 2008, 05:25 PM   #1
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Noisy pre-amps, or something else?

I was shooting an interview recently w/ a Sennheiser ME66 and a Sony ECM-77B, both hard-wired with great XLR cables. It sounded nice through my MDR7506s BUT the SECOND I put it into record mode I started getting noise.

What do you guys think that can be, noisy pre-amps, mechanical noise from the tape-transport? I'll try to do some testing on the DR-60 without recording to tape and see what that's like.

Otherwise, I guess it's one more reason to buy a mixer.

I'm kinda stuck though until then, I really want to make sure to get the best quality I can for these interviews I'm doing, and I won't have a mixer.
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Old January 6th, 2008, 05:46 PM   #2
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Dear Craig,

I suggest that you contact Steve House as he may be able to assist.

Where is the ME66 located? Is it mounted on the camera?

Is the noise on both channels?

What camera are you using?
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Old January 6th, 2008, 05:49 PM   #3
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what camera ?

does it have a built in LCD ? sometimes LCD's or their support circuts can leak 16khz or so, which is there refresh freq. turning the LCD off can make it go away. mainly a problem in consumerish grade cameras

did the room AC kick in ? change something in lighting ? I've picked up hum from HMI's that ran at 60hz. Even if you ran on a AC supply, it can send nasties into the camera power and make problems, which is why I run batteries 99% of the time.
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Old January 6th, 2008, 08:09 PM   #4
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Is it going to tape? Could it just be the headphone preamps?
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Old January 6th, 2008, 09:22 PM   #5
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More questions for you. Maybe related to Phantom power? Are you powering the ECM 77B from battery or Phantom?
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Old January 7th, 2008, 01:52 AM   #6
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Hey guys, thanks for the questions.

Here's some more info to help.

It's a Sony HVR-V1U. I am hearing it on both the Sony ECM77B channel and the Sennheiser ME66 channel. The ME66 has been boomed, or mounted on a stand right above the subjects in everything so far. No camera mounting. Which is why I'm surprised, because everything until I hit record sounds crystal clear... I'm HOPING it's the headphone pre-amp as someone suggested and that it's not actually recorded to tape that way. I'm anxious to review this footage on a computer asap.

I tried comparing with the ECM77B on Phantom and without. I did not however, try closing the LCD so I will try that tomorrow.

I thought it was the tape transport or something, because I can consistently re-create the noise going away and coming back simply by putting it into rec or standby. However, I tried recording a scene with just the DR60 today, and it came through on that also. So now I'm thinking it's not the tape transport, and I'm back to the pre-amp theory.

Unless it may be because I disengaged the MIC NR feature (noise reduction) in both channels. I'm going to try to remember to turn that back on tomorrow and maybe that'll tell me more.
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Old January 7th, 2008, 01:54 AM   #7
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Also, I haven't been using AC power for my camera, it's been running on battery for everything so far. The DR60 as well.
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Old January 7th, 2008, 06:13 AM   #8
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Dear Craig,

May I suggest that you run the following test?

Using long XLR cables, put the camera in another room, with the door closed, leaving the microphones where they are.

If you do not have long enough cables, just put the microphones in one room, and put the camera behind a closed door.

Also, you could put a heavy blanket over your camera for a second test.

I am trying to rule out camera noise.



We would like to rule out the headphone amps in your camera, so please let us know if the noise is on the tape or not.


Could you please describe the noise for us?
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Old January 7th, 2008, 07:58 AM   #9
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Adding to Dan's diagnostics. You mention you're using the DR60 external hard drive. Is the noise present if you remove the drive and record direct to DV tape? Wondering if there could be electrical noise from the hard drive itself or the connecting cable leaking into the audio.
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Old January 7th, 2008, 08:44 AM   #10
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I'm not too great at describing sound/noise, but it sounds like it could just be room ambient noise. It's the same kind of operational sound I could imagine coming out of an old VCR. Not sure. Since I can't really describe it I'll try to upload a WAV file somewhere and put up a link asap.

I reviewed some footage we shot yesterday without the DR60 attached and it was on their also. So I've tested each so far, exclusively.

I'll run some more tests right now.
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Old January 7th, 2008, 08:49 AM   #11
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Could just be noise in the camcorder headphone out when the camera starts recording. Or some kind of confidence playback while recording sound. Try playing back some of the footage and see how it sounds. This has been a common problem in many camcorders from professional on down that the headphone out sounds different when recording than it is in E to E. Figuring out if it is a problem or just a monitoring issue is a bit of the art.
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Old January 7th, 2008, 09:34 AM   #12
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On some Sony camcorder models of the past, engaging the Mic Noise Reduction created artifacts that were very noticeable.
That could have changed, but I would experiment with actual voice tests in realistic conditions before I used the on-camera NR.
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Old January 7th, 2008, 09:46 AM   #13
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Okay, I've just tried not attaching any mics to it at all, and just engaging the recording. It's there. So it's not the mics or the mic-preamps it seems.

I tried doing another recording straight to DR60 with NO tape and the sound WASN'T there. It was purely clean. When I put the tape in, the noise came back. So it seems to be the tape transport.

What's peculiar is that if I'm simultaneously recording to tape AND the DR60, the noise comes through on the DR60. Does that make sense to anyone? It'd be great to be able to record to tape as well, and not exclusively to the DR60 but if that's what's introducing the noise I guess I'll have to.
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Old January 7th, 2008, 09:53 AM   #14
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Quote:
Originally Posted by Craig Irving View Post
What's peculiar is that if I'm simultaneously recording to tape AND the DR60, the noise comes through on the DR60. Does that make sense to anyone? It'd be great to be able to record to tape as well, and not exclusively to the DR60 but if that's what's introducing the noise I guess I'll have to.
Dear Craig,

When you recorded to tape and the DR60, was the microphone attached and active or was it unplugged for this test?

I would run a test with the microphone plugged it, but the gain set to 0.

Also, I would put my ear to the tape transport. See if you can hear it.
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Old January 7th, 2008, 10:28 AM   #15
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The last two tests were done w/ no mics attached. Trying to reduce to the fewest variables.

I'm uploading a wav now. I have a musician friend though who just tried using a Waves program with it and managed to get the noise out, so I guess it's something that COULD be handled in post-production, still though maybe I should shoot the rest of my interviews using exclusively the DR60.

Uploading a WAV file now. I analyzed it in Sound Forge, looks like a constant frequency that hits in constant intervals.
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