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calibrate FP33 and DVX100: tone at -20 or -12?

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laura sinnott
calibrate FP33 and DVX100: tone at -20 or -12?
on Nov 20, 2008 at 2:47:42 pm

I'm working with the DVX100 and FP33. As a standard, I send tone (line out) from the mixer at 0VU, and set my camera levels to -20dB or -18dB. On the DVX100, the notch on the meters that transition from white to red apparently represents -12dB. I've always set the levels to this notch, not realizing it was -12dB. All other mixers I know (which aren't a WHOLE lot, mind you) have also set tone to this mark on the DVX100.

Does anyone have any insight into WHY it's -12dB, and if this indeed is the right combination of levels to use? [0VU on mixer, -12dB on camera]

While we're on the subject, I believe it's also true the mixer has about 14dB of headroom after 0VU, correct?


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Peter Groom
Re: calibrate FP33 and DVX100: tone at -20 or -12?
on Nov 20, 2008 at 9:08:56 pm

HI Laura

It really doesnt matter what level you send tone at. What IS important is the relationship between that tone and the peak of the audio that follows it. That relationship has been worked into an industry recognised standard and therefore its easiest to follow that standard.

In the UK it is 1k tone at -18dbfs = PPM 4. The peak audio level is then +8 db above that. But to re iterate it is a standard that people follow and take for granted, but you could pefectly correctly put tone at -14 to PPM 5 as long as you document this on the tape report that this is the rule that you are adopting for delivery so the receiving engineer could calibrate to that.

I dont really know what the US standards are, but all this spec will be documented on the website tech area of whoever the ntaional broadcasting governing body is in your country. In the UK its the EBU (European Broadcasting Union).

The same rules apply to the bars that preceed delivery copy. The Bars can be 75% or 100% and it doesnt matter as long as you document what is usd.

Peter

Dubbingmixer



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Ty Ford
Re: calibrate FP33 and DVX100: tone at -20 or -12?
on Nov 20, 2008 at 9:39:11 pm

Hi Laura,

Guess the book hasn't got there yet. :)

-20 on the DVX100. I don't know where -12 came from, maybe back in the analog days when shure mixers and analog cameras were used.

On all of the Sound Devices mixers, you send tone which shows up reading 0 VU on the mixer. Choose the correct mixer output to camera input, e.g. mic out to mic in, line out to line in.

Set you camera meters to -20. Set your mixer to read VU AND Peak, or PEAK only if it doesn't do both. You now have from 0 to +20 on the mixer to have safe audio. With my Sound Devices 442 mixer, I set the internal limiter threshold to +16. I also try to keep my levels peaking at about +16, which is where the first red LED of the display lights. That gives me 4 dB of Ooop! room. With the limiter in, that's usually enough.

Regards,

Ty Ford


Want better production audio?: Ty Ford's Audio Bootcamp Field Guide






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Reid Fiester
Re: calibrate FP33 and DVX100: tone at -20 or -12?
on Nov 22, 2008 at 1:48:53 pm

Hi Ty, a couple questions....

Is the master gain control a attenuator or a more complex control?
Do you use it?
Are you close to max on the 442 gain/faders to run that hot out?

Best,
Reid

Reid Fiester
Frederick, MD


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Ty Ford
Re: calibrate FP33 and DVX100: tone at -20 or -12?
on Nov 22, 2008 at 8:42:49 pm

[Reid Fiester] "Hi Ty, a couple questions....

Is the master gain control a attenuator or a more complex control?
Do you use it?
Are you close to max on the 442 gain/faders to run that hot out?"


Frederick! Excellent!

More complex than what? It's a knob. I don't use it much, mostly to bring down all pots evenly.

Don't understand the last question.

Regards,

Ty Ford

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide






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Reid Fiester
Re: calibrate FP33 and DVX100: tone at -20 or -12?
on Nov 22, 2008 at 9:10:04 pm

What I want to know is what is behind the master gain control on the 442. I can't read wiring diagrams well enough to understand whether it attenuates the existing signal down 6db from its max when set at 0db or does it engage a separate powered gain block to kick up the level?

Is it better to use it if levels are showing up low on a downstream input or is it better to run the gain/faders close to full out. I recently worked with a JVC-250 that seemed to need much hotter levels than I am used to.

Any thoughts??
Thanks,
Reid

Reid Fiester
Frederick, MD


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Ty Ford
Re: calibrate FP33 and DVX100: tone at -20 or -12?
on Nov 22, 2008 at 9:20:39 pm

Reid,

I don't know that JVC camera. I set the master to 0 dB (the center detended position), make sure I'm line out to line in or mic out to mic in and send tone to teh camera. I set tone at -20. I run th e442 meters in VU/Peak mode and I don't have any problems.

Regards,

Ty Ford


Want better production audio?: Ty Ford's Audio Bootcamp Field Guide






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Jordan Wolf
Re: calibrate FP33 and DVX100: tone at -20 or -12?
on Nov 25, 2008 at 7:53:15 am

I routinely use a DVX100A/B and a Shure FP24. I really wouldn't look at the levels in dBFS until you capture it.

The camera's manual says that it's Line Level input has a sensitivity of 0dBu. On the FP24, 0=0dBu. So if you output the 1kHz tone at 0dBu to the input set at Line Level and leave the control(s) at the center position, the levels should then be calibrated.

I, personally, go by the +4dBu professional standard, so I set my gains a little higher on the FP24 and the camera. I keep an eye on them and, as long as the mixer and the camera are calibrated, clipping on one will equal clipping on the other.

ONE CAVEAT (anecdotal story): I accidentally ruined the on-location dialogue for a movie scene last year because I mistakenly forgot to set the input to Line Level.
I calibrated my levels - both sets of meters showed everything as clean and not clipping. BUT I couldn't hear that I was overloading the inputs on the camera because I was using the headphone output on the FP24. Always double-check your settings - it can never hurt. (ADR worked out and you can barely tell the audio was dubbed; check it out here, if you want to)

Now then, back to my class project!

Wolf
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