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Sony HVR-A1 and HDR-HC Series
Sony's latest single-CMOS additions to their HDV camcorder line.


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Old January 18th, 2007, 05:07 PM   #1
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Hvr-a1 Xlr Audio Noise

Hi all,

I'm pretty new to the DV stuff, but I'm learning the ropes step by step. I need your help in determining if my camera, a HVR-A1, is showing normal operation or not. The camera was bought a few months ago. A while back, I knew little about audio, but now know a little bit more what to watch for. And I finally got me some software and good headphones. So here is my situation.

Recording audio with the XLR box but with no microphone attached, and with the audio level all the way down in manual mode, I measured the noise/audio hiss to be at about -55/-54 dB. That's still pretty much noise to the ear. Not very quiet. In fact between zero audio gain level and the audio level all the way down, noise level was a pretty much constant at -55 dB. Is this normal for the HVR-A1?

Also, in the lowest frequences, there's a mechanical/electrical rumble sound to be heard if I monitor the sound with the levels way up. It's like very low frequency ticking sound - I think maybe from electrical current. Is this normal? I can see it clearly in Soundtrack Pro in the frequency spectrum view in logarithmic readout. Pretty constant interval spikes in the lowest frequencies.

All sound was monitored on my Mac through headphones.

Please don't tell me I have a bad lemon.

Timmy
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Old January 19th, 2007, 07:55 PM   #2
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Hi Timothy,

It sounds a bit like the motor noise of the camera being recorded. I don't own the A1, but with other cameras that I have used the solution is always to get the mic off the camera and isolate it. This is done with a shotgun style mic and a rubber band shock mount to isolate noise. If you check out my link to www.thej-rod.com you will see a solution to mounting a shock mount and mic of your choice on your camera.
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Old January 20th, 2007, 02:10 AM   #3
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Hi,

Most microphone amplifiers are very noisy if you leave the mic input open. The input should always be connected to a low impedance load, either the microphone, and in your case, a suitable dummy resistor.

If you want to check the noise level in your system, and you obviously want to do that without a mic, then you must do the following:

Get two male XLR connectors. Open them and solder a 150 ohm resistor between terminals 2 and 3. Preferrably a small 0,25W metal film type. Close the XLR-connectors and attach them to the mic inputs. Now you should get better results.

Christian
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Old January 20th, 2007, 03:23 AM   #4
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When Jay Rose checked the S/N ratio for DV cameras (http://www.dv.com/features/features_...cleId=23902929) he measured similar low values for the Sony PD150 and Canon XL1. He concluded that even a cheap minidisc recorder easily outperformed the built-in audio in many prosumer video cams. Your -55 dB S/N ratio may be normal for the camera, although I don't know that for sure.

Have you checked the performance when the inputs are set to line-level and manual? I haven't measured it, but my HVR-A1U seems quieter when I use an outboard (Sound Devices) preamp and bypass the camera's internal preamp. Even so, I wouldn't be surprised if a decent minidisc recorder is quieter.

Best wishes,
Peter
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Old January 20th, 2007, 03:24 AM   #5
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Hi,

Jeff, as I wrote, I tested it without a mic attached, so it isn't the motor noise that is being recorded - at least not through the mic. The rumble is probably circuity problem.

Christian, you maybe right about the open mic port in general, but I also tested it with a mic attached and turned the level way down, and the noise level was still just as high (-54 dB). Shouldn't the noise be less, the lower I turn the level with a mic attached? It's a pretty good mic, a Rode NTG-2, with double shielded XLR cable. Despite almost no difference in peak level, there is difference between the noise pattern when the mic isn't attached and with the mic attached. With the mic attached, there's less high frequency noise coming through. So it's only slightly cleaner.

Thanks for the replies. It would be great, though, if there were other HVR-A1 owners I could compare with.

Timmy
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Old January 20th, 2007, 03:33 AM   #6
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By the way, this is what Jay Rose wrote in the article (http://www.dv.com/features/features_...cleId=23902929) about how much of a S/N ratio you actually need:

"Although 16-bit sound is capable of 84 dB s/n below -12 dBFS, that kind of quiet is almost never achieved in practical equipment. If you're shooting for theatrical release or heavily processed broadcast, 60 dB is desirable. Corporate and event videographers can get by with 45 dB or so if the voices don't have much dynamic range; more is needed if there are volume swings."

Best wishes,
Peter
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Old January 20th, 2007, 03:39 AM   #7
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Hey,

thanks Peter for the link. That's very helpful.

It would be very nice if you could measure your S/N on your HVR-A1, if you got the time, that is. But the link is very helpful indeed.

Timmy

Last edited by Timmy de Groot; January 20th, 2007 at 04:16 AM.
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Old January 20th, 2007, 03:52 AM   #8
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I don't measure much difference between Mic and Line level setting. Noise is still high. It would be nice if the noise was closer to -60 dB. I probably need to invest in a outboard preamp, because the internal will suck when I use the gain. Maybe I should invest in an audio recorder at times when I need really clean sound.

Timmy

EDIT:

The thing is, the HVR-A1 is being distributed not under Sony's consumer division but the professional/business division. One should think they'd put more care in the Pro division products.
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Old January 20th, 2007, 12:55 PM   #9
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Quote:
Originally Posted by Timmy de Groot
The thing is, the HVR-A1 is being distributed not under Sony's consumer division but the professional/business division. One should think they'd put more care in the Pro division products.
I'll try and measure the noise base level when I have the chance.

In Sony-speak, the definition of a pro-level camcorder would seem to be anything with XLR inputs, regardless of performance. That clearly doesn't match your definition of what a pro-level piece of equipment is, but that's how Sony sees it.

Personally, in spite of its several shortcomings, I think the HVR-AIU is a phenomenal camcorder for the price. I don't know of anything else that produces images of this quality (and has phantom power for mics) in a package so small and lightweight. I even appreciate the very consumer features of a built-in still camera and Night Shot. For out in the field portability (say, hiking or backpacking) the A1u is heaven-sent.

IMO, for recording better quality audio, a small stand-alone recorder with decent preamps is well worth looking into.

Best wishes,
Peter
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Old January 20th, 2007, 04:27 PM   #10
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Quote:
Originally Posted by Peter Rhalter
I'll try and measure the noise base level when I have the chance.

Personally, in spite of its several shortcomings, I think the HVR-AIU is a phenomenal camcorder for the price. I don't know of anything else that produces images of this quality (and has phantom power for mics) in a package so small and lightweight.
Hey,

Thanks Peter. Yeah, the HVR-A1 is a very neat camcorder. With a lot of care and attention, as to lighting and miking, it can be used as a pro piece. I am happy with the gear as it's compact and it was relatively cheap for a beginner's cam. I'm slowly getting all the info I need regarding equipment and such, but it's not always easy.

Timmy
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Old February 5th, 2007, 12:31 PM   #11
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Quote:
Originally Posted by Timmy de Groot
H
It would be very nice if you could measure your S/N on your HVR-A1, if you got the time, that is. But the link is very helpful indeed.
It isn't scientific, but late last night when it was fairly quiet around here I did a small test of how quiet the HVR-A1U can be. I set the camera's audio signal to line level and the channel gain to manual (I left the gain level in the center). I then connected an AKG Blue Line Mic with the CK93 hyper cap on it (rated by AKG at 17 dB self-noise, which is pretty middle-of-the-road) through a Sound Devices MM-1 preamp to the channel 1 XLR jack.

I recorded to the camera about a half minute of the sound of my fingernail gently tapping on both a wooden cabinet and the wall. The preamp was at maximum gain, +66dB. According to the meter, my peaks were somewhere around -30dB or -25dB, so these were pretty low-level sounds. I then transfered the recording to my computer via Final Cut Pro and opened it with an audio program (Amadeus II).

I have to say I was pleased with the result. Without amplifying the sound I had no trouble hearing the tapping but any background hiss was inaudible (to me, at least) The silent moments looked quite flat in the time line. I then used the software to amplify the sound 3x. Now the tapping was prominent and the background hiss was audible but not intrusive. I amplified the file 3x again for a 9x total. At this level, the hiss was clearly noticeable and the tapping was loud.

My conclusion is that, using a good microphone and outboard preamp, the HVR-A1U is capable of making sound recordings in a quiet environment that, from the standpoint of noise, should be usable for many purposes.

Best wishes,
Peter
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Old February 6th, 2007, 03:02 AM   #12
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Timmy,

I use an NTG2 and a Sennheiser G2 reciever on my A1. I kept the reciever off for the control side (to record only internal noise) and kept the mic on to compare it with room tone. I measured about -52db to -53db hiss in Audition from the camera. I agree that this seems a bit high, but up until now I haven't noticed it so it doesn't seem to get in the way when recording levels are set properly.

Here's a 15-second sample so you can compare to your own: http://www.flashfiresystems.com/~vlad/A1_Hiss.zip

This sample was taken with the included Sony shotgun mic since that's what I had mounted at the time. XLR box settings = (Ch1, Mic, On, Line, Off). Levels set on auto.

-Sean
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Old February 6th, 2007, 04:17 AM   #13
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with the gain on auto, then the odd noises are not unusual on quite a few bits of kit commonly available. The main reason is that the cameras have too much available gain - in some kind of attempt to pick up the sound of moths wings beating - but seriously, advanced gain on many items of pro kit brings up all sorts of noises. Shorting the input and applying maximum gain, doesn't give a realistic result. In almost every case in normal use, the gain setting is much lower, taking the noise floor right down. It's quite similar to the problems with cameras with gain settings for video - you can apply 18dB or morevideo gain, and images appear, but they are grainy and pretty grotty. Turn the gain down and they get better. If the camera can hear the tape mechanism, and the zoom motor, then there seems little point increasing the gain any more?
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Old February 20th, 2007, 01:42 PM   #14
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Thanks everybody

Hey,

I'm so very sorry for the late reply. I've been quite busy. Thanks Peter for making the time to test your equipment and help me out. You're very kind. And thanks to Sean too. That sound file was very helpful. I'm much obliged for all the comments, tests, and experience reports. This is a very helpful and friendly forum.

Timmy
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