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Old October 6th, 2005, 10:45 PM   #1
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Microphones: Preamp or in-camera amping

I'll start of by saying I'm rather new to the pro-audio world, but in my latest venture with my new AT897 and the Beachtek DXA-6, I have discovered the notion of "Mic" level vs. "Line" Level signals. This question stems from my recent adventure with my faulty FX1 found here:
http://www.dvinfo.net/conf/showthread.php?t=52310

Basically, my question is this: is there any inherent benefit to amplifying the microphone signal (especially that of the AT897 since it is more quiet) before putting it to the camera? Or is a camera's mic amplification usually sufficient for getting the least amount of noise/hiss? I'm thinking of exchanging my DXA-6 (Phantom-powered XLR adaptor) for the DXA-8 (same adapter with pre-amps and limiters). Would this be a better setup in general or is it unnecessary to have pre-amps?

I appreciate all thoughts on this. Thanks!

Chad Terpstra
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Old October 7th, 2005, 04:11 PM   #2
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Was this a stupid question?
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Old October 7th, 2005, 04:33 PM   #3
 
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It's not at all a stupid question, just one that perhaps got overlooked.
No camera has great, smokin' "oooh-aaahh" audio features in the sub 20k range. That said, the cams are usually sufficient. However, there are benefits to using a good pre if the mic isn't sensitive enough or hot enough at output. If your cam has phantom (which the FX1 doesn't) then you'll find you get better audio than with a battery. Depending on the source you're recording, you may find you need additional gain to get the mic to where it's clean and robust, yes. However, this can vary. I'd be using a Studio Devices or Beachtek with any FX1 or other cam that doesn't have phantom and XLR inputs. But that's just me.
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Old October 7th, 2005, 04:42 PM   #4
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Quote:
Originally Posted by Chad Terpstra
Was this a stupid question?
Not at all. Most DV camera's have somewhat marginal microphone preamps so you can often record a better signal with a higher quality outboard preamp or preamp/mixer and feed line level signals to the camera. That being said, for dialog it might not matter very much and for a lot of video with less than great sound other factors such as mic placement be having a greater impact. No matter what, a mic on the camera 15 feet away from the talent isn't going to give great dialog recording.

The DXA-8 looks like a good unit. Also consider the Sound Devices MM-1 preamp with headphone monitor and Sound Devices MixPre 2-channel mixer.
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Old October 7th, 2005, 06:01 PM   #5
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This begs the question: Which has better pre-amps? The Sony Z1u or the DXA-8 (or something else that will mount on a FX1)? Anyone know?

It would kind of ironic if the FX1/DXA-8 combo producded better sound.
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Old October 7th, 2005, 07:31 PM   #6
 
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I don't know that it's ironic, it's quite possible. But the Z1 U produces better images no matter what. I only have the Z1u, no FX1, so can't test my DX8. The DX8 plugged into a GL2 doesn't sound better than the Z1 does, no. You'd think it might, because the GL2 is PCM, but the converters in the GL2 aren't all that hot themselves.
I'll see if I can get my hands on an FX1 in the next few days.
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Old October 7th, 2005, 09:20 PM   #7
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Thanks for your replies. For a moment I was begining to think I'd posted a silly question.

Steve: It's a shame about not getting good audio from 15 ft. away... I really had my heart set on that... ;-)

DSE: Interesting notion about the Z1 getting better images. It is a topic for another thread, but if you could point me to relavent posts/articles discussing that, I would be interested. I'd also like to hear your results on testing the FX1 + DXA-8 combo.

For the moment, I've decided to keep my DXA-6 because my camera needs some serious repairs in the preamp section (refer to begining of thread), and I can't afford both things right now. However, these beachteks seem to hold their value pretty well on ebay, so I will likely consider a new solution in the future. Does anyone know of a product similar to the Beachtek DXA-8 which can be mounted to the camera? I looked at the Sound Devices, but they don't fit to the camera (that I saw), which can be a plus when you're just "shoot'n." So far it seems like the beachteks are the only ones that do this.
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Old October 7th, 2005, 09:57 PM   #8
 
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Chad, if you wanna have an FX1 vs Z1 discussion, head over to the HDV forums here on DVInfo.net.

Having spent time with both, having written many an article about both, and being intimately aware of the differences of the two cams, the only time the FX 1 can look as good as the Z1 is when both are in automode and ignoring all electronic differences between the two. Optically they're the same camera. That's where the similarities basically end.
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Old October 12th, 2005, 09:44 PM   #9
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Quote:
Originally Posted by Chad Terpstra
is there any inherent benefit to amplifying the microphone signal (especially that of the AT897 since it is more quiet) before putting it to the camera? Or is a camera's mic amplification usually sufficient for getting the least amount of noise/hiss? I'm thinking of exchanging my DXA-6 (Phantom-powered XLR adaptor) for the DXA-8 (same adapter with pre-amps and limiters). Would this be a better setup in general or is it unnecessary to have pre-amps?

I appreciate all thoughts on this. Thanks!

Chad Terpstra
www.terpstar.com
The answer depends on how good the external preamp/mixer is and how the camera input is configured.

If the external preamp/mixer is of higher quality than that of the camera then, yes performance will be improved by using an external preamp/mixer.

HOWEVER...

if the camera input is line level AND achieves that line level input by simply putting a pad in front of a mic preamp, the audio is still going through another preamp. This usually does little to improve the quality of the audio.

The sound devices preamps are better. The limier is quite transparent, allowing higher record levels which result in less system noise.

Clamping a mixer to your camera may be convenient, but it doesn't get you the best audio. It's a limitation.

Regards,

Ty Ford
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Old October 14th, 2005, 03:13 AM   #10
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Quote:
I don't know that it's ironic, it's quite possible. But the Z1 U produces better images no matter what. I only have the Z1u, no FX1, so can't test my DX8. The DX8 plugged into a GL2 doesn't sound better than the Z1 does, no. You'd think it might, because the GL2 is PCM, but the converters in the GL2 aren't all that hot themselves.
I'll see if I can get my hands on an FX1 in the next few days.
DSE: Have you managed to get an FX1? I'm very interested in your comparison of the Z1u audio compared to the FX1/DXA8 audio. Also, do you think you could likewise test the FX1 with an AT897 or AT4073a connected to a Mini Stereo Male to 3-pin XLR Female cable (like the this Hosa cable at B&H)
If you could post some sample clips of each setup from the same audio source that would be very helpful?
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