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Old Jun 8, 2008, 4:27 PM   #41
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I am afraid preamp is useless, becouse I think cameras own preamplifier circuit generates all that electric noise, with preamplifier you can only amplify cameras preamplifier circuit and generate even more noise. But you can try if you really want if you have better idea than myself, but first explain how it would be theoritically possible, my all reasoning will say there will be just more hissing electricity noise if you amplify it more?
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Old Jun 8, 2008, 10:57 PM   #42
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It's not to get a cleaner sound, but only to increase sound pressure level for a wider db range.
When recording loud sounds, (live bands) the noise isn't so much a problem as SPL overload.
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Old Jun 8, 2008, 11:32 PM   #43
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AtariJedi wrote:
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Hello all, I was wondering if any of you know what the output voltage is of the standard AHD electret mic? The reason I am asking is I have just bought an AHD (haven't received it yet) and I have started to design a preamp circuit for another electret mic and I am wondering what kind of gain I should have, although I have been thinking about using a trimpot to make it variable gain. I'll be tying it into the power supply of the AHD. Component count so far is 5, including microphone.

I also think I know why the mic gives off so much noise, Electret mic's usually have a built in FET based pre-amp, usually its pretty decent for mass production circuitry, but some of them are just shoddy and generate or pick up and amplify noise. So a 2nd preamp, with noise rejection should help.

I have seen another pre-amp circuit floating around, I can't remember who drew it, but sorry to say, it isn't a pre-amp. The circuit consisted of the mic, a resistor, a capacitor and a battery, this is just the proper way to power an electret microphone, but isn't a pre-amp. Any kind of amplifier needs at least 1 transistor.

Also, I have thought about possibly trying to move the microphone to the front, but I am unsure if there would be enough room to mount it there.

When I get my AHD and have built the circuit and tested it, I will post some before/after demo's of it. Hopefully it will work and make nice clean sound.
Really looking forward for those results! and of course a wiring schematic

Is this the wiring you were referring to earlier: http://forums.steves-digicams.com/fo...25&forum_id=92
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Old Jun 8, 2008, 11:36 PM   #44
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It seems to me that one of the major problems is that the sound is getting distorted because it is clipping. With a variable preamp, you could prevent that.
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Old Jun 8, 2008, 11:40 PM   #45
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To bwmpowere36m3:

That isn't the exact one I was talking about, but after reading it more closely, that is the exact same circuit, which isn't a preamp, but just how you should power an electret microphone.

Also, my schematic should be relatively simple, as far as I can tell it will only be 5 parts, I might try it 2 ways, a simple common-emitter amplifier with 1 transistor, or an inverting amplifier with an OP-AMP. We will see which one works better, and is easier to make.
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Old Jun 8, 2008, 11:45 PM   #46
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Yea I was thinking of using that circuit when I found it, since the poster said it worked great for him. I got a A-HD+ which I want to use for in-car recording and I know a drawback of the 720P was that it would "click" or sound terrible in-car... not sure if it was the high SPL levels or the "wind-noise" or just a large range of high SPL "noise" that would over load the mic.
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Old Jun 9, 2008, 4:43 AM   #47
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Isn't one potentiometer enough for preventing clipping, I think it is. Adding more resistance to cameras own preamp circuit should prevent clipping, you don't need additional preamp circuit if you only want to prevent clipping, just lowering mic input should do it. My problem is hissing sound in very quiet environments. Even good old Aiptek DV5700 has better sound in quiet environment, you just can't improve it anyway in AHD200. Aiptek must redesign their audio circuit, I just complained this to Aiptek support, that even with new 2.0 firmware audio is bad in quiet environments. I haven't got any answers yet, but wait and see what they say. Only way to be able to record good sound in quiet environment is using external audio recorder or to use my old DV5700 which has good audio quality, but bad video quality and my DV5700s LCD screen is not working very well, I get usually white screen when I turn it on.
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Old Jun 21, 2008, 3:01 PM   #48
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Hey I got this camera awhile back and I can't stand the sound. I tried recording my little brothers basketball game and I couldn't understand a single word anyone was saying. I would like to mod this camera to be able to support external microphones, but I have no experience in electronics.

The tutorials that I've seen so far look fairly simple enough, but I don't know what's best. Some of you have been talking about preamps, but that sounds more complicated, while others are leaving the original mic in and just adding a jack so that you can plug a higher quality mic in. I like this second way the best, as it looks simple enough. I particularly liked the last picture, with the small black box on top, the jack. Does this really help the quality of the microphone? I just want to be able to understand what people are saying with it distorting. Thanks for all your help so far. This gives me hope for my camera. I'm not going to attempt a mod until I have all the materials and know exactly what I'm doing.

Also, that wide angle lense looks awesome. How is the quality and what model is it?
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Old Jun 21, 2008, 5:17 PM   #49
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Sorry to say but if you buy external audio recorder which costs atleast as much as your Aiptek camcorder you get better sound otherwise you have to be happy what you got. I've tried so many modifications to improve sound in AHD 200 that I can say its not worth it, there should be warning sign in this camcorder about bad audio quality :-)

Here is my fix without rewiring mic:

http://www.youtube.com/watch?v=6nKfdbWFtgg

I just disassembled my DV5700 which has better audio with even smaller mic than AHD200 has. I think Aiptek engineers forgot how to make good sound quality with inexpensive components when they were designing AHD200.

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Old Jun 21, 2008, 8:24 PM   #50
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What about those youtube videos? They were using A-HD camera's, and it sounds a whole lot better than my camera. Any improvement will make me happy, I just want to be able to hear what people are saying in the videos I take.
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