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Old May 10th, 2009, 01:15 PM   #1
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HM100 - very hissy pre-amps???

Got my HM100 on Friday and so far I am very pleased with it - except for one thing. The mic pre-amps on my camera appear to be very hissy. The sound itself is pretty ok assuming that my AKG will be superior to the shotgun that came with it, but I can clearly hear the hiss basically at all audio level settings except when turned to 0. And itīs the same whether I just monitor the audio in the camera or after I imported it to my NLE. Coming from a Canon HV20 and a XH-A1 Iīd say the pre-amp is just as bad as the ones in the HV20 - unless my camera is defective. What is your experience? Any problems so far? If I have time later on I will try to post an example...

Last edited by Matthias Krause; May 10th, 2009 at 06:23 PM.
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Old May 10th, 2009, 02:49 PM   #2
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I thought mine was really noisy but then I saw that I was hearing the noise coming from the automatic gain control on channel 2 if there is nothing plugged in. It tries to turn it all the way up. Changing channel 2's input to channel 1 or setting it to Line and 0 made the noise on that go away.

After that at normal levels I didn't hear very much noise at all. There is a little hiss but I wouldn't say it was "very hissy."
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Old May 10th, 2009, 04:07 PM   #3
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Glad to hear that, Elvis. Please ignore one of my follow-up questions on the other thread re: your experience with 'hissy audio'.

Not having a camera in hand yet, I'm not sure I understand exactly the button and setting options you are referring to, but I'm sure it will be clearer once I take delivery this week.
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Old May 10th, 2009, 04:10 PM   #4
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I tried some higher end studio mics and they were very quiet so I think everything is alright.
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Old May 10th, 2009, 04:55 PM   #5
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So here is an example with the mic that comes with the camera. The audio level is on manual 5-6, I am about one foot away from the mic. The second channel is on manual too and dialed down to 0. The hiss/noise is pretty bad, if you ask me. Is that how your cams sound too or did I get a faulty one?
Thanks,
Matthias
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File Type: wma Untitled.wma (279.2 KB, 120 views)

Last edited by Matthias Krause; May 10th, 2009 at 06:24 PM.
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Old May 10th, 2009, 11:35 PM   #6
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So - do I expect too much or what? Really doesnīt sound good to my ears but maybe Iīm doing something wrong? It would be great to hear some comparison from another cam so that I can decide whether to send it back or not...
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Old May 11th, 2009, 12:39 AM   #7
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Hi Matthias.

I've gotten very interested in the HM100 after seeing footage by Phil Bloom and Matt San.

But before I start losing interest in the camera after reading of your audio difficulties, I was just wondering if you'd followed Elvis's advice exactly.

The bit about "the noise coming from the automatic gain control on channel 2 if there is nothing plugged in".

Presumably, if you have a mic plugged in to channel 2 then all should be well.

If not, Elvis's advice was to change "channel 2's input to channel 1 or setting it to Line and 0".

Elvis said that if you dial it down to 0, then you also have to set it to "Line". From a photo of the HM100 audio controls which I found online, the switch for Line is under the label "AUDIO INPUT". Yet you've stated that the "second channel is on manual too and dialed down to 0". According to the photo I'm looking at, the "Manual" setting is part of a different switch labelled "AUDIO SELECT".

Could you just re-check what you've done and report back.

It's important for me to know if the HM100 really does have bad audio hiss.

Thanks.
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Old May 11th, 2009, 01:20 AM   #8
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Audio Test

There was more hiss than I thought when I initially tested it but turning off Channel 2's automatic leveling does cut the audio quite a bit. The only thing I did to the audio was normalize it (bring it up to zero where it was mostly at -12 dB)

http://files.me.com/elvis/6lf6fh.mp3

The nicer mics that required less gain and were nearer to me were much quieter so a nicer shotgun would probably help there and something on a boom pole.

Update: I checked and it does make a big difference if the channel is on Mic vs Line but not Mic vs Mic 48V. That makes sense.
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Old May 11th, 2009, 01:30 AM   #9
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Hi David,
I checked all combinations I could think of with no luck. The hiss is almost gone if both channels are on line-in, which is logical since it turns off the internal pre-amp and the only hiss I would be hearing is from the headphone pre-amp. I am not sure what Elvis is talking about though since his scenario would mean that there is some kind of bleeding between the channels going on. In my example you hear just one channel, I deleted the other one in my NLE. And as I stated, both channels were on manual, the one I didnīt use (channel 2) was dialed down to 0. It sounded the same when it was on line-in (which should make no difference unless the would be some kind of bleeding...).
I have a hard time believing that JVC would consider what I am getting "professional sound". So I hope that I just have a defective unit and will see if I can send it back to B&H (unfortunately Iīve already thrown out the box...).
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Old May 11th, 2009, 01:48 AM   #10
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Originally Posted by Matthias Krause View Post
Hi David,
I checked all combinations I could think of with no luck. The hiss is almost gone if both channels are on line-in, which is logical since it turns off the internal pre-amp and the only hiss I would be hearing is from the headphone pre-amp. I am not sure what Elvis is talking about though since his scenario would mean that there is some kind of bleeding between the channels going on. In my example you hear just one channel, I deleted the other one in my NLE. And as I stated, both channels were on manual, the one I didnīt use (channel 2) was dialed down to 0. It sounded the same when it was on line-in (which should make no difference unless the would be some kind of bleeding...).
I have a hard time believing that JVC would consider what I am getting "professional sound". So I hope that I just have a defective unit and will see if I can send it back to B&H (unfortunately Iīve already thrown out the box...).
There was more noise than I originally thought. Doing my test in the above post showed the noise I originally noticed but when you take it away there is still plenty of noise there. I will just work around it. I will try a better shotgun and see how that affects the amount of needed gain.
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Old May 11th, 2009, 01:49 AM   #11
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Elvis, I checked you examples and there are some inconsistencies that I donīt understand. I suspect that you have the "CH2 Input" set to "Input1" which would mean that you are mixing the channels? But anyway, could you please do me a hugh favor and post the result of a simple test?
Unplug any mic, just have the handle and the mic cable connected to the cam. Put the "CH2 Input" to "Input2". Put "Audio Input" to "Mic" for both inputs. Put both channels on "Manual" and dial both channels up to 6 and record 30 secs or so. And than dial both channels up to 10 and record 30 seconds. I would be extremly interested to compare that to my cam. Here is what my cam sounds like if I dial both channels up to 10 - the noise floor is somewhere around -42db:
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File Type: wma Noisefloor10.wma (308.4 KB, 88 views)
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Old May 11th, 2009, 01:57 AM   #12
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Originally Posted by Elvis Ripley View Post
I will just work around it. I will try a better shotgun and see how that affects the amount of needed gain.
But thatīs my point. From my experience you should be able to turn the gain up to at least 5 or 6 before you get any noticeable hiss. Otherwise it just means that the pre-amps are crap. Yes, you can work around it just like I did with my HV20. Been there, done that. But I donīt want to since I spent a lot of money for a camera that promises to be suitable for pro work.
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Old May 11th, 2009, 01:59 AM   #13
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Quote:
Originally Posted by Matthias Krause View Post
Elvis, I checked you examples and there are some inconsistencies that I donīt understand. I suspect that you have the "CH2 Input" set to "Input1" which would mean that you are mixing the channels? But anyway, could you please do me a hugh favor and post the result of a simple test?
Unplug any mic, just have the handle and the mic cable connected to the cam. Put the "CH2 Input" to "Input2". Put "Audio Input" to "Mic" for both inputs. Put both channels on "Manual" and dial both channels up to 6 and record 30 secs or so. And than dial both channels up to 10 and record 30 seconds. I would be extremly interested to compare that to my cam. Here is what my cam sounds like if I dial both channels up to 10 - the noise floor is somewhere around -42db:
Channel 2 was set on Input 2 for my test.

Here is the results of what you wanted.

http://files.me.com/elvis/fqkq9g.mp3
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Old May 11th, 2009, 02:06 AM   #14
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Wow, thatīs a big difference: Your cam dialed all the way up to 10 checks out at around -50db... Seems like there is something wrong with my cam... Should not make a difference, but are you using .mov files or .mp4?
Thanks a bunch!
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Old May 11th, 2009, 03:01 AM   #15
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.mov

For your test I took the QuickTime file and dragged it into Compressor and chose mp3 320 kbits so it should be as close as it can be and still be an mp3.
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