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.

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?

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.

Is it going to tape? Could it just be the headphone preamps?

More questions for you. Maybe related to Phantom power? Are you powering the ECM 77B from battery or Phantom?

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.

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.

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?

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.

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.

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.

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.

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.

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.

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.

http://www.badongo.com/file/7205625

Thanks for your interest everyone.
Here's a wav that shows what I'm getting.

Craig,

I tried listening to your clip.

I do not have all of my tools available here at my office. Also, my office has normal "Office Noise" making it less than perfect.

However, I could not hear any significant noise.

Could you check your file by downloading it yourself. Then please let me know if you hear the noise.

I Dl'd your clip but it was silent....

sounds line a power supply problem in the camera. its not physically generated noise... unless the mic pre amp board is literally microphonic from the vibration of the motors running, but that would really be a long shot, although possible with a defective component. sounds far more like the camera's power supply is borderline and when the motors kick in for the tape transport, they start making dirty power because they are on the edge. its also possible that the motors themselves are putting noise into the camera's power, but very very unlikely. sounds like its time to send it in for service.

Haven't listened to the clip but your description sounds like the tape transport is creating some electrical noise which is getting into the audio circuitry before it goes to record. I would bring this up with your dealer and the manufacturer directly as it might just be your unit but it also could be a problem with the whole series of cameras.
Also you should record it to tape with out the Harddrive unit connected to make sure it is just coming from the Tape drive

There is nothing on that WAV file you uploaded. Not even a single waveform.

We'll need something where you're actually recording audio to see what kind of noise you're getting. Perhaps a snippet of that recording you made on your last shoot?

I came across this same problem back in June. That was what brought me to this forum. The noise is there when you record. Also it has a very noisy cheap sounding headphone out. The gain knobs are best left at their centre dent 5 setting too if you want to avoid noise, bit pointless having them.

My final verdict was that the sound of this model camera is poor to worse.

Would be interested in what conclusions you come to. Particularly turning off the lcd.

Why Sony can't sort the audio out on their cameras I don't know. Just used the new DSR 450 and the headphone out has noise and latency. One of three units sounded considerably less bad as well. The phono/line outs are said to be good though as is the recording apparently. Just a crap headphone amp circuit.

Keep us posted on your test results. I was not the pwner and only had limited time to test the model I was using. Recorded double system audio in the end.

The clip does have a good sample of the noise, it is just very low level. I imported it into ProTools and raised the gain. Sounds like internally generated camera noise. It consists of a low frequency rhythmic motor boating and a high frequency whine. Can't you get decent Signal/Noise ratio by feeding a good audio signal?

Hey guys.

I re-downloaded that clip from the link I sent I sent you and I'm kinda surprised only a couple of you heard it. You actually shouldn't really need to touch the gain, I was playing back the clip in VLC Player and just boosted the headphone volume and heard it right away, it's constant. Also using the speakers of my laptop (though they're poor quality) it was obvious to me.

It's not really that low-level to me, it's actually quite loud I feel w/ the interview subjects talking.

I opened it in Sound Forge myself to look at it, and immediately I didn't see waveforms either, then I zoomed in quite a bit and did notice a pattern of dots (I really don't know much about spectrum/frequency analysis though)

Here's a picture I posted of how it looks to me in Sound Forge 9.

it is -58 db referenced to digital 0. That's pretty low.

Hmmm. Alright so I guess my inexperience with audio is starting to show. It seems the consensus is that -58db is a very low level signal, and though I'm hearing a noise in my headphones it sounds like it's to be expected. Although it's confusing that it doesn't sound that low to me in my headphones. I guess I just expected absolute silence, since I can record a clip directly to HDD that doesn't have this silence (though I haven't yet examined it in Sound Forge, I'm still curious to know if it's -58 or something different).

I'm going to be taking all your tips. I have been keeping my gain at around 6-7 (no higher usually). I'll try reducing it even more if I can.

Thanks again everyone for your help, I appreciate you taking the time to download the clip and help me out on this. I really didn't want it to come across as "this is a serious problem" but more along the lines of "this is what I am hearing and should I worry about it" kind of thing.

So I'm glad to hear it's normal.

Dear Craig,

How did your shoot go?

Hi Craig:

Just to let you know, Sony Corporation has a proud and cherished lineage of selling consumer and prosumer camcorders with amazingly bad sound quality. I owned a TRV-900 for about 10 years and it was sent to Sony Service for new microphones, new audio pre-amps and new circuitry and it still sounded terrible, Sony would just mark on the service papers, "acceptable sound quality for consumer camera", which didn't help.

The PD-150/VX2000 and PD-170/VX2100 were widely acknowledged as the worse sounding prosumer camcorders that had ever been sold. Hiss, noise, low dynamic range, they had it all. It's interesting, since Sony went to HDV, I have not heard many complaints about the sound quality until your post. I shot with a Z1 for the past few years before I bought an HVX and the Z1 had okay, if not great sound quality.

This doesn't help you solve your issue and you should realize, based upon past history, there may be no way to solve this issue. Sony acknowledged that the PD-150, which was a very popular camera in it's day, had really poor sound quality and recalled them under a warranty fix but I tested and measured several "fixed" cameras and they still sounded horrible. That was the first and last time I have heard of Sony owning up to manufacturing a camera with really lousy sound.

All I can tell you is that I would complain to Sony really loudly and perhaps they will do something for you. The only reason they did with the PD-150 was because of grass roots mass complaining from thousands of PD-150 that all of the cameras had sound so bad that the cameras were basically only usable as a film camera, meaning you had to use double system sound.

This is all ancient history now as people have forgotten mostly about the whole Sony making lousy sounding prosumer cameras debacle but I do recall because I was involved in the whole thing. For some reason, Sony, who used to be the premier electronics company, in about the year 1998, forgot how to engineer audio circuits. It is strange that the VX-1000, the first Sony MiniDV camcorder that many of us owned and used alongside our $70,000.00 Betacams, had excellent sound quality and only used 32kHz sample rate even. But after the VX-1000, the preceding models all had terrible sound quality. This is one of the main factors I switched to Panasonic camcorders when the DVX-100 came out. Not so much for the 24P, more so for the high quality sound circuitry. All of this poor sound quality debacle is outlined in this article I wrote back in 2002. http://www.kenstone.net/fcp_homepage...ion_sound.html
Page down about 2/3 of the way through the article and you can see my comments on how I hoped that the soon to be introduced VX-100 would have good sound quality and you can see my report card grades for all of the previous Sony models.

I hope that you can get this resolved. Do you have access to another of the same model (have a friend/client with the same one?) that you could compare yours to? I wonder if this issue is endemic to the model or if you just ended up with a bad copy?

All my best,

Dan

I just got back last night, so I haven't had a chance to review much of the footage yet.

I don't have another V1U, but I'm going do some testing w/ an FX7.

I'm not ready to put-down the V1U though. I've had some fantastic performance with it so far. I've had it for a year and this is the first I've noticed anything unusual. Though I am confident that if there is an issue with my camcorder that Sony would take care of it under warranty. I'm aware of previous concerns people had with the PD-150, and such, but so far I've been quite pleased with the audio quality on the V1U. This was just a peculiar experience that I thought I'd run by you guys before I had the opportunity to do more testing. Again, since audio experts here (who know way more than I do) don't consider that noise to be an issue nor have they reported anything similar, then we shouldn't get carried away with any assumptions. Especially considering my inexperience with analyzing audio.

All I know is that everything sounded crystal clear and free of noise when I was setting up interviews using an ME66 and an ECM77B when the camera was in in STBY mode, and then it only began when I switched into REC mode. It's possible the noise was exaggerated in my 7506s, so I'll have to try them on my monitors at home tonight.