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Old May 18th, 2007, 12:46 PM   #1
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External VU meter for edit bay and test tones

I am becoming tired of the vast discrepancies between the audio meters on my decks and the mixers. I can calibrate for tone but once the program is going everything is all over the place. The mixer seems to be accurate but it's disturbing when the Beta and DVCam decks are very different.

Does anyone use an external VU meter? Is there a place I can download test tones to ascertain which frequencies are not activating the VU meters as strongly?

Thanks.
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Old May 18th, 2007, 01:35 PM   #2
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Originally Posted by William Hohauser View Post
I am becoming tired of the vast discrepancies between the audio meters on my decks and the mixers. I can calibrate for tone but once the program is going everything is all over the place. The mixer seems to be accurate but it's disturbing when the Beta and DVCam decks are very different.

Does anyone use an external VU meter? Is there a place I can download test tones to ascertain which frequencies are not activating the VU meters as strongly?

Thanks.
What editing software do you have? Most such as Soundforge, Audition, Vegas, etc have tone and noise generators built in. If you don't have access to something like that, let me know what tones you want and what levels and I can generate something for you.

It sounds like you're noting discrepancies in the meters on various pieces of equipment. This is to be expected, actually, because analog VU meters, Peak Power meters, and digital peak meters all have different ballistics and calibrations and so they won't read the same. As a result, the same tone won't indicate the same thing on a DVCam's digital meters as it does on a BetaCam's analog VU meters. Plus there's differences between the various meter's responses to sine wave tones versus pink noise versus speech.

And to echo Chris's post below, Dorroughs seem to be the cat's meow for a lot of users. Very interesting white papers on their web site, well worth a visit even if their meters are over your budget.
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Last edited by Steve House; May 18th, 2007 at 03:53 PM.
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Old May 18th, 2007, 01:44 PM   #3
 
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There are many free test tone gen's out there, here is one I use if I don't feel like building one in Sound Forge:
http://www.downloadpipe.com/review_12473.html
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Old May 18th, 2007, 02:47 PM   #4
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Industry standard audio SPL meters out here in LA are mostly from a local company called Dorrough. They're around $400 a channel, but they make different kinds of meters, so it's best to get informed before you start spending the big bucks.

Paradoxically, one interesting piece of gear I use all day long is by Behringer. It's the DEQ2496 and it has all sorts of metering, spectrum analysis, room RQs, stereo spread, feedback detector, and even a room pinking setup when used with a specific (and inexpensive) calibration mic, also from Behringer.

I have this 1U unit set up right in front of me and it listens to my studio monitors. It has full audio pass-through, unbalanced, balanced, and digital, so it's directly in between my mixer's master outs and my (powered) NFMs.
Mostly I use it as a realtime spectrum analyzer so if I hear a hum or a plane going by, I can see the freqs I have to dial out immediately.

However, I've used it as a SPL QC device (it has total peak program memory, etc), as regular VU meters with adjustable weighting, ballistics, etc., a straight up SPL reader, and to do a quick and dirty pink on a room I've not sat in before.

That's a lot of bang for around $300, so if it breaks I'll buy another one.
It hasn't yet, though. I was concerned about Behringer's Chinese build quality when I first bought mine, so I bought two. That was five years ago. I think I sold my backup around two years ago, unused.

HTH, YMMV, etc.
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Old May 18th, 2007, 10:20 PM   #5
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Thank you all for your responses.

I'll check out the Behringer device as soon as possible.

The test tone program looks great but I'm in the Mac world. I was looking to find some aif or wav files of various calibrated tones to load into Final Cut since that's the way I'm outputting programs.

I wish I still had that sweep generator from my ham radio days.
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Old May 19th, 2007, 12:22 PM   #6
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William,
Sounds like you are seeing the discrepancies between Analog and Digital levels on various machines. If you are outputting from Final Cut Pro to DVCAM and are using tone at -20DB and mixing levels to -12DB on loud spots (like many people do) then your Betacam levels will be recorded too loud if you set your tone to 0DB. If you set the tone to -8DB on the Betacam then you will get a correctly recorded analog level but your tone will not be standard. The best thing would be to record the tone at 0db and turn down the program recording 8DB so it lines up properly on playback.
This is happening since digital tone is not really set at what most people use as the loudest signal they record. In Analog, tone was supposed to be very close to the loudest signal to be recorded.
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Old May 19th, 2007, 09:48 PM   #7
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Quote:
Originally Posted by William Hohauser View Post
I am becoming tired of the vast discrepancies between the audio meters on my decks and the mixers. I can calibrate for tone but once the program is going everything is all over the place. The mixer seems to be accurate but it's disturbing when the Beta and DVCam decks are very different.

Does anyone use an external VU meter? Is there a place I can download test tones to ascertain which frequencies are not activating the VU meters as strongly?

Thanks.
Hi Bill,

While an external VU meter is helpful, I think the problem is the difference between analog scaling and digital scaling. No meter will help you there.

The other issue is VU meters (with needles that read RMS) on your analog gear and digital meters on your digital gear that read peak.

You can smack a betacam meter to, what, +4, +6. That's an RMS VU meter. It's too slow to measure the peaks, that can be significanlty higher.

With digital metering 0 dB is all you get and those camera meters read Peak.

So while you set tone at 0 VU on an anlaog meter, you set tone on a digital camera or deck at -20 db and allow peaks to read from there to (typically) run at -12 dB to -10 dB. You have all the way to 0 dB on the digital meters.

Hope this helps.

Regards,

Ty Ford
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Old May 20th, 2007, 09:30 AM   #8
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The UVW Betacam SP decks have a much slower VU react time than the PVW series. I was fortunate enough to have one of each and that was how I noticed that it was very easy to make the signal too hot on the UVW betacam sp deck without ever kissing red on the meters.

I find a solid audio level on a UVW betacam sp deck is for the led's to read between -10 to -2 when doing uncompressed audio recording. If you are skeptical that this is the range simply take a betacam sp recording done in a UVW and put it into a PVW betacam sp deck (with the audio set to preset mode) and watch the VU needles go crazy on The PVW deck even though on the UVW deck you may think the signal was average at best.

It's been fascinating for me to see the "diversity" of betacam sp audio level recordings I have been given over the years when I am asked to do a run of VHS or dvd copies. Sometimes the signals are perfect, sometimes they are so hot they peg the needles in the PVW and I have to override them to bring them back to normalcy. lol, I can actually tell if a facility is using newbies or not by how the audio gets laid down on their betacam sp master tapes.
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Old May 21st, 2007, 07:23 PM   #9
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Thank you all for your responses.

I found some wav files that spanned 20hz to 20,000hz by twenty increments. I created a timeline, low to high, and calibrated the levels so that the frequencies were at the same level as the test tone that ships with Final Cut, "-12". That wasn't hard as the wav files were all at the same level. I played the resulting program back and had these results. The Mackie mixer was dead on at "0" until it reached about 18,000hz and above where the VU meter had a slight dropoff. The biggest problem was with the UVW BetaSP deck just as a previous poster had mentioned. It was all over the place. Set with the FCP test tone at "0", the UVW started low with the low frequencies, went into red +3 and over around 3000hz and stayed there until about 10,000hz where it dropped to -10db. White noise had a similar effect. While FCP's meter and the Mackie meter agreed with each other at -12/0, the Beta VU hovered around -10db.

While this may not be the best way to test, it gave me a good idea of how to interpret the BetaSP deck VU meters.
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Old May 21st, 2007, 07:34 PM   #10
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Quote:
Originally Posted by William Hohauser View Post
Thank you all for your responses.

I found some wav files that spanned 20hz to 20,000hz by twenty increments. I created a timeline, low to high, and calibrated the levels so that the frequencies were at the same level as the test tone that ships with Final Cut, "-12". That wasn't hard as the wav files were all at the same level. I played the resulting program back and had these results. The Mackie mixer was dead on at "0" until it reached about 18,000hz and above where the VU meter had a slight dropoff. The biggest problem was with the UVW BetaSP deck just as a previous poster had mentioned. It was all over the place. Set with the FCP test tone at "0", the UVW started low with the low frequencies, went into red +3 and over around 3000hz and stayed there until about 10,000hz where it dropped to -10db. White noise had a similar effect. While FCP's meter and the Mackie meter agreed with each other at -12/0, the Beta VU hovered around -10db.

While this may not be the best way to test, it gave me a good idea of how to interpret the BetaSP deck VU meters.
One additional point to make about the UVW betacam sp deck, if the audio signal that is being recorded by the UVW is compressed, the UVW will probably give you a more accurate read than if you are feeding uncompressed audio to the deck. I'm not suggesting to only feed the betacam sp deck compressed audio, just that you can probably trust the LED readouts moreso than with an uncompressed audio level. On the positive side, I have found the UVW deck to have a pretty darn good e to e pass through for the video image, and I actually get good quality audio masters by basically avoiding red level of LED's for uncompressed audio. lol, it's kind of like an analog deck with digital videotape attributes.
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