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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, 2008, 06:36 PM   #1
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HC7 Microphone Audio

When using the HC7's built-in mic set to auto I've noticed on two occassions that the recording has a high pitched noise in the background. It seems to go away on it's own, and I've heard it in both indoor and outdoor recordings. I'm wondering if it's the auto gain turned up as high as it can go and it's picking up the camera's internal noise. Anyone heard this on a HC7 or similar camera and know what to do about it?

Thanks.
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Old January 20th, 2008, 03:25 PM   #2
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I have an HC7 and the best thing to do is to not use AGC and use manual audio control, If you hear a buzzing sound, that's the internal noise of the tape.

If you're in a quiet location, set the volume to 3 below center. If you're in a really loud place, set it to 2nd from the left since the lowest one clips at around -20 or less db. Also using an external mic like the Rode Videomic in low sensitivity could prevent clipping at loud events.
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Old January 23rd, 2008, 01:57 PM   #3
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Quote:
Originally Posted by Jack Zhang View Post
I have an HC7 and the best thing to do is to not use AGC and use manual audio control...
Why not just use AGC? The manual controls are a pain to operate and you will cause clipping and/or too low levels constantly. The only problem with agc is that the level will fluctuate, but so what? You still need to change your levels constantly when its on manual.

And if some hiss pumps itself up in lower passages, just pull it back down in your editing program.
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Old January 26th, 2008, 08:40 AM   #4
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Thanks guys. I was out for a week and I'm just beginning to catch up. My suspicions are that it's the AGC at full sensitivity causing the problem. In both recent cases the audio I was recording was quiet. The noise I hear is hiss along with a buzzing at around 5Khz. I filtered some of it in Vegas.

I'll try using manual volume when appropriate, but it surprises me that the Sony would have engineered the AGC to be so aggressive that it would pick up the internal camera noise.

Jack, I also have a Rode VideoMic but I haven't used it much with the HC7. But when I have used the VideoMic I'm very happy with the results.
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Old January 26th, 2008, 03:49 PM   #5
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My method is to record in manual then add a compressor/soft limiter for optimal results. I don't have a Rode VideoMic but am gonna have to borrow a external mic for a upcoming uber loud event (not a concert, a school event).
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Old February 4th, 2008, 09:34 AM   #6
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Follow-up post:

The External Mic I was gonna borrow had higher sensitivity then my in-cam Mic. I'm just gonna use the in-cam mic then.
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Old June 20th, 2008, 05:52 PM   #7
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Camera Repaired

Hey Gang,

I reopened my original post from January to let HC7 owners I sent my HC7 in for repair of the the tape microphone noise I described in January. The problem never improved and I couldn't find any explanation for why sometime the noise was there, and other times it wasn't, even just moments later while shooting the same location but after pausing the camera for maybe less than a minute.

I sent it back to Precision Camera (per Sony) just before the 1 year parts warranty expired, but I still had to pay labor, which I got at a reduced rate with Sony's help. According to Precision Camera, they replaced the drum, recalibrated, and realigned the camera.

I did a quick couple checks and so far no noise. I only wish I would have sent it back within 90 days after purchase so I wouldn't have had to pay any labor charge. I'm sure the problem was there from the beginning.

If the noise returns I'll post again.
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Old July 4th, 2008, 04:58 AM   #8
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My HC9 Has a Similar Problem

When there is no outside sound to be recorded, apparently the AGC on my HC9 raises the sensitivity level and the squeaking and rasping noises of the rolling tape mechanism are very audible on the recording, when using the built-in mikes. Even when I use an external mike mounted in the shoe, these noises are still on the recording. When there is some outside sound, these internal noises disappear. Since I always shoot with a shoulder-mount, that has an extended arm for an external mike, it is positioned about 8 inches away from the camcorder and no operating noises are picked up. So, the problem is solved for me, unless I wanted to do some hand-held shooting.

I made the mike support arm with Kevlar, that blocks most vibrations and sounds that might otherwise pass from the camcorder, through other types of material. I used epoxy resin with the Kevlar cloth, that was laid up on a form that had the right bends and angles. The finished arm is about 3/16-inch thick and 1.5 inches wide and has 8 layers of 5-oz. Kevlar cloth. Kevlar is a great material for dampening sound and vibrations. That's why they use it in some of the better speakers, to kill reverberations. A Kevlar canoe will run quite silently through the water, while one made of standard fiberglass will give out a roaring sound. Kevlar is not easy to find for sale in small quantities. An online search will produce the names of a few dealers that will ship as little as one yard of it, if you pay their minimum order charge. It's not cheap, but worth the expense where its unique qualities are needed. Industrial type shears are the best for cutting it and must be sharpened frequently. Actually, I've used Fiskars brand scissors to cut it, but after only a moderate amount of use, they are ruined. One thread of it is so strong, that it takes several hundred lbs. of force to break it. Since I have built kayaks and paddles from it, I have scraps on hand. If there's a local manufacturer that uses it for any purpose, remnants could probably be bought from them.

If anyone wants to see the HC9 on the shoulder-mount, with the mike holder, here's the link:

http://farm4.static.flickr.com/3222/...dec888cf_o.jpg

Last edited by J. Stephen McDonald; July 4th, 2008 at 05:49 AM.
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