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Old January 29th, 2004, 12:34 AM   #1
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calibrating the SVU-1

I just got an SVU-1, one of Beachtek's portable VU meters. I'm a little confused by the directions that came with it as to how to calibrate it so I can monitor audio levels correctly. I'm using a Canon XL1s. Part of my confusion, I guess, is because the directions mention "not letting the audio peak past 0 db, but -12 on the XL1s is considered 0, or the ideal peak level at least. . .and it's all very confusing to this guy. Any of you guys know how to do this? Explicit detailed instructions would be excellent.
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Old January 29th, 2004, 03:11 AM   #2
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Nothing will be lost in your audio signal until the levels get to zero. It's digital so when they do get there, they're gone. Total distortion.

If you are trying to dub to an analog format, like beta, then you need to keep in mind that analog formats have some overhead. So if you set reference at -12(or -20) and keep you levels around there you can have short plosives that go over and analog equipment will handle them fine.

If you are staying digital all the way to delivery, then still think of -12 as a safe place to stay to give you a little room to work. You never know when someone will lean toward their microphone.
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Old January 29th, 2004, 07:47 AM   #3
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I guess I could record tone from an NLE to a tape, and then play the tape back through the camera's VCR function, to give me a reference?
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Old January 29th, 2004, 06:08 PM   #4
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Alright, still need some clarifcation, as I seem to be retarded.

I recorded, from my NLE, to tape, 1Hz for some reason) tone, at -12 db. I calibrated it so that on playback through the camera, -12 on the camera's VU meter was also -12 on the SVU-1. I also recorded tone at 0db, with the same result. One thing that worries me, though, is that I can't get the SVU-1 to go into the red (the +3 and +6 indicators), even when I can hear the sound distorting in the headphones. If 0 db is the maximum the XL1s can handle, then when I hear distortion, shouldn't I be able, on the SVU-1 to see the +3 and possibly +6 light up? It never peaks past the yellow (0 db), no matter what.
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Old January 29th, 2004, 11:49 PM   #5
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Call Harry at Beachtek, he made it so he knows best how to explain it. He's a very helpful type.
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Old January 30th, 2004, 01:28 AM   #6
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Yeah, I've been in email contact with him. . .but I always figure two (or more) heads are better than one.
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Old January 30th, 2004, 08:42 AM   #7
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Well if you want this external indicator to react like an analog vu, then you should set your reference tone at -12 from your camera to be 0 on the SVU. Now if you keep your signal around 0 on the unit with a few peaks into the red, your audio on the camera should still have be a strong enough signal to avoid the noise floor and have a little bit of headroom to avoid clipping.
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Old January 30th, 2004, 08:54 AM   #8
 
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I'll wager that you'll often/usually see distortion at -12. Panasonic calibrates analog to -14, Sony to -18, JVC to -18, Tascam to -18, and the ATSC spec is -20. http://www.atsc.org. You can read 2 white papers there for free. Then you have to pay to read the rest.
I don't know where the -12 thing comes from, but it's pretty common on the web.
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Old January 30th, 2004, 09:01 AM   #9
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DSE,

Distortion on what? He's recording to an xl1, it shouldn't distort until he pegs zero.

Interesting that manufacturers have established totally different relationships between their analog and digital gear. Won't it be nice when everything is digital except you monitors.

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Old January 30th, 2004, 09:14 AM   #10
 
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If he's sending tones from an analog device to create a -12 signal to a digital device, chances are he'll be hitting zero with audio going into the XL1. If not, chances are still good in a direct transfer that the XL will be too hot to a beta deck. For the meter to "react like an analog VU" and be accurate, -12 isn't enough attenuation.

After re-reading his/your post, I recognize there is a different meaning than I'd read the first time though...so I'll leave it at that. I've got digital INPUT speaks, and even they suck. Yes, it would be great though if all things were digital, or at least a metering display standard could be observed. It's confusing as heck to most everyone, including me, because it's difficult to always remember what meter you're using.
I use a Dorroughmeter for most things, it helps a LOT
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Old January 30th, 2004, 10:12 AM   #11
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I'm just saying. . .if I see "-12" or something (any level) on the Camera's VU meter, don't I want to see the same thing on the SVU-1? I bought it so I could monitor audio (besides headphones of course) by another method then squinting at the camera's tiny built in VU meter. I'm just trying to make sure I'm calibrating it to get that result--sorry if I complicated things.
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Old January 30th, 2004, 10:14 AM   #12
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I'm just saying. . .if I see "-12" or something (any level) on the Camera's VU meter, don't I want to see the same thing on the SVU-1? I bought it so I could monitor audio (besides headphones of course) by another method then squinting at the camera's tiny built in VU meter. I'm just trying to make sure I'm calibrating it to get that result--sorry if I complicated things.

That zero things still bugs me though. . .
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Old January 30th, 2004, 10:16 AM   #13
 
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Since I don't know the VU1, I'm gonna assume it's calibrated to analog, not digital. If it is, you'll see a different reading on it than you will on the XL. Trust the XL, and calibrate the SVU1 accordingly.
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Old January 30th, 2004, 10:25 AM   #14
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I'm sorry; how do you mean?
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Old January 30th, 2004, 12:47 PM   #15
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Harry from beachtek emailed me this: Does it sound about right? I didn't see how it makes sense before, but I think I do now, too low is too low, and too high is still to high, the numbers are just different:

It appears that the XL1s cannot put out more signal after 0 VU. I believe the Canon owner’s manual suggests setting the audio levels to the -12 dB mark. In that case, You may want to calibrate the SVU-1 so that 0 VU on the SVU-1 corresponds to -12 dB on the camera. This way, you will plenty of breathing room before you reach the distortion level.
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