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SD442's VU vs SQN's PPM?

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Andrew Williamson
SD442's VU vs SQN's PPM?
on Nov 17, 2008 at 4:57:57 pm

So there I am - Visa in my left hand, mouse in my right hovering over the 'add to cart' button, ready to purchase a good old SQN. But then something catches my eye: a shiny new Sound Devices 442 and for the same price...

After having spent enough on hiring location mixers to have purchased one, I feel it's time to buy one. Having essentially used SQNs pretty much exclusively for every sound recording job I've ever done, it kinda makes sense to buy an SQN. However, I'm always hearing great things about Sound Devices mixers and know their Recorders aint half bad! I especially like the idea of easy compatibilty between the 442's direct outs and a lovely bit of kit like the 744T. But heres the thing...

Here in the UK pretty much all broadcast specs require the audio limits to have maximum peak at PPM6 (1kHz tone lining up PPM6 at -10dBfs, with PPM4 lined up at -18dBfs). As the SQNs I tend to use have a BBC PPM meter this means gain riding dialogue nicely around the PPM4-PPM5 mark with the limiter catching sudden outbursts and keeping you safe just below PPM6. This saves a lot of time in post and keeps the Dub quite simple - which is often a life-saver on some of the tight turnarounds we usually have.

Now, as the SD442 uses VU display - how does this work for monitoring? Do you take maximum peak as equating to +8 VU? Where does the limiter kick in?

I know Sound Devices have a Nordic PPM version, but I am still curious as to what the Film and TV audio legals are for the US and if they are set by VU?

As PPM and VU balistics are different is there anyway I can monitor VU on the 442 and be happy I'm still broadcast legal? or should I ignore the shiny and go back to my equally shiny, but familiar SQN.



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Ty Ford
Re: SD442's VU vs SQN's PPM?
on Nov 17, 2008 at 10:15:01 pm

[Andrew Williamson] "Now, as the SD442 uses VU display - how does this work for monitoring? Do you take maximum peak as equating to +8 VU? Where does the limiter kick in?

I know Sound Devices have a Nordic PPM version, but I am still curious as to what the Film and TV audio legals are for the US and if they are set by VU?

As PPM and VU balistics are different is there anyway I can monitor VU on the 442 and be happy I'm still broadcast legal? or should I ignore the shiny and go back to my equally shiny, but familiar SQN."


Hello Andrew and Welcome to the Cow Audio Forum.

Film and TV legals are all over the road here. Discovery has one set of "MUST" standards, satellite has another, broadcast iand cable are a wild and wooly freakin' circus.

The limiter on the 442 is adjustable from +4 to +20. I have mine set a +16. It's not a brick wall limiter, but a very good sounding one.

The O VU to dBu reference is VERY adjsutable. Look on page 20 of their manual.
http://www.sounddevices.com/download/guides/442_en.pdf

If you have additional questions, my suggestion is that you email jon Tatooles at Sound Devices, give him my regards and ask the questions directly. One thing I know for sure, Sound Devices is always good on their word. jon_tatooles@sounddevices.com

Regards,

Ty Ford


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






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Peter Groom
Re: SD442's VU vs SQN's PPM?
on Nov 20, 2008 at 9:17:59 pm

HI Andrew

You really cant use a VU to try to guage a peak value. This is because the attack of a VU is very fast, but the decay is fast too, and so unless the audio is at a constant level to read, the next audio will average out the level of the first audio. Thus the VU will not ever reach the true peak which is what you need to see. Its a mean value. It will give an approximation - but speaking as a studio dubbingmixer, if you recorded footage supplied to me on a VU and the overs caused problems in the dub, that youd never even seen on location meters, it would be only a short while before we had a telephone conversation.

I say stick with PPM for accurate peak monitoring.

Cheers

Peter
dubbingmixer



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Ty Ford
Re: SD442's VU vs SQN's PPM?
on Nov 20, 2008 at 9:21:46 pm

Peter is correct. In case I didn't make it apparent, teh Sound Devices 442 displays peak and VU simultaneously.

Regards,

Ty Ford


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






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Andrew Williamson
Re: SD442's VU vs SQN's PPM?
on Nov 20, 2008 at 10:06:07 pm

Hi Ty & Peter,

Many thanks for your responses - that answers my question nicely.

I obviously knew that VU is a mean value indicator and not appropriate for peak monitoring - hence my question about how (and possibly why) Sound Devices use VU metering on their mixers! :) also leading to my curiosity as to US broadcast legals. That the 442 displays peak and VU simultaniously explains a lot.

I've had the headache many times before of having to dubbing mix programs with audio recorded without PPM metering and though its no biggie, it does turn the Dub into an automation fest of gain riding.

I have a feeling my hard earned cash is gonna have to go with old familiar, partially due to ease of access to parts in the unlikely event of failure (SQN being based on the Isle of Man), but also, as I'm sure Peter would agree, it would be better to monitor using the same metering that delivery would have to be set by.

Many Thanks!

Andy



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