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Old September 25th, 2008, 11:29 AM   #1
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302 Mixer?

I purchased this mixer and love it, solid build and great design.

I am a little unclear about one thing, the led meter and numbers. 0 seems to be the Max point, and the first of the red led's but yet the meter goes well over that to +20.

When recording I being simple minded would think it should never hit red, but this means the average level is well under the 0.

Can anyone explain where you like the average and the PEAK to be.

Thanks
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Old September 25th, 2008, 11:48 AM   #2
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SD302 is an analog mixer and confirms to the old analog age metering standards. When analog tape was used as a recording medium 0 dBVU was the theoretical optimum recording level. In real life the tape was always driven with higher signal, as it is self limiting and does not suddenly clip. For that reason metering went higher than zero, +12 dBVU was about the highest peak level with analog tape. Also, as the meters were not peak reading, even when the average levels hovered around Zero, the real peaks were around +12 but nobody saw them and tape took it gracefully.

Now, with digital, Zero is a Zero and there is nothing beyond it, exept harsh distortion from clipping. +20 dBVU on SD302 equals 0 dBFS on digital systems.

I repeat: +20dBVU on SD302 is the same as 0 dBFS on a digital recorder. 0 dBVU on SD302 equals -20 dBFS on digital systems, and so on.

This means that you should run the meters on SD302 at RMS + peak setting, the solid lights showing average levels and the lone jumping led showing the peak. This peak can and should hit red occasionally, but not the last one. This would place the peaks around -3 on the digital device. Having the peaks hitting the yellow most of the time places the levels at around -20 to -8 dBFS, which is perfect.

That's all there is to it, analog and digital scales are offset by 20 dB. Peak levels should read 20dB higher on SD302 than on the camera.

Turn on the test tone on the SD302 and adjust the camera meters to show -20. If you want you can turn on the full level test tone from the menu and set the camera to read 0 dBFS with that. After doing this all level setting is done with the mixer and camera potentiometers are taped in place.
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Old September 25th, 2008, 12:35 PM   #3
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Quote:
Originally Posted by Petri Kaipiainen View Post
SD302 is an analog mixer and confirms to the old analog age metering standards. When analog tape was used as a recording medium 0 dBVU was the theoretical optimum recording level. In real life the tape was always driven with higher signal, as it is self limiting and does not suddenly clip. For that reason metering went higher than zero, +12 dBVU was about the highest peak level with analog tape. Also, as the meters were not peak reading, even when the average levels hovered around Zero, the real peaks were around +12 but nobody saw them and tape took it gracefully.

Now, with digital, Zero is a Zero and there is nothing beyond it, exept harsh distortion from clipping. +20 dBVU on SD302 equals 0 dBFS on digital systems.

I repeat: +20dBVU on SD302 is the same as 0 dBFS on a digital recorder. 0 dBVU on SD302 equals -20 dBFS on digital systems, and so on.

This means that you should run the meters on SD302 at RMS + peak setting, the solid lights showing average levels and the lone jumping led showing the peak. This peak can and should hit red occasionally, but not the last one. This would place the peaks around -3 on the digital device. Having the peaks hitting the yellow most of the time places the levels at around -20 to -8 dBFS, which is perfect.

That's all there is to it, analog and digital scales are offset by 20 dB. Peak levels should read 20dB higher on SD302 than on the camera.

Turn on the test tone on the SD302 and adjust the camera meters to show -20. If you want you can turn on the full level test tone from the menu and set the camera to read 0 dBFS with that. After doing this all level setting is done with the mixer and camera potentiometers are taped in place.
Thanks for such a detailed explenation.
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Old September 25th, 2008, 04:42 PM   #4
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Nice going Petri, your explanation of the 'old analogue age' versus the digital, 'Zero is Zero' is very well written.

It should be at the front of the SD manual and maybe a sticky here Chris?

Cheers.
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Old September 25th, 2008, 09:29 PM   #5
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I'm pretty sure it's in the manual.

Regards,

Ty
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Old September 26th, 2008, 03:31 AM   #6
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It probably is if you understand what you are talking about in the first place.

I've read the manual a number of times and have spoken to SD too. The manual wasn't very helpful, SD were very helpful on the phone. Petri's explanation takes it a few stages further.

Maybe SD should pay Petri to rewrite the manual. Seriously.
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Old September 26th, 2008, 04:20 AM   #7
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Often the question tells that just giving the exact answer is not going to help much. A good, working answer also explains enough of the backround to make it understandable. Understandable answer is something people remember. When answering we should try to imagine the situation the asker is in, how much he/she knows and if he/she is actually asking the right question, even.

(my parents were teachers...)
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Old September 26th, 2008, 07:06 AM   #8
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Petri,

Well said, but if mfgrs followed that rule, manuals would be huge and people wouldn't be able to find the right section anyway. :)

When Final Cut Pro arrived here, the box was as big as a truck battery. I have never seen so many manuals for one suite of software.

Estimating the average users comprehension level is very challenging. I thought about it a lot when I was writing my little book on location audio.
AudioBootcamp.html

I put contextual examples and even conversations in the book to provide additional "handles" that might allow others to pick up the information.

So far, I haven't heard from anyone that they didn't "get it." Then again, some folks are all about the quick fix for their specific problem and don't want to spend time learning the info that would really help them solve LOTS of problems.

Regards,

Ty Ford
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Old September 26th, 2008, 08:08 AM   #9
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Quote:
Originally Posted by Ty Ford View Post
Well said, but if mfgrs followed that rule, manuals would be huge and people wouldn't be able to find the right section anyway. :)

True, when getting pro equipment better be prepared to get a manual which exactly tells how to do all possible things, but not one which would tell WHYor WHEN do it or WHAT actually happens when you do certain adjustements. It is a tool, and the user is presumed to be informed enough to use it.

Just like when you buy a hammer, you are not going to get a manual which tells you why and how to build a house or a cupboard.

As some pro level audio & video tools are now cheap enough for dedicated amateurs, boards like this are invaluable information tools. Still, getting and reading a basic book would not hurt, at least you would get your questions right.
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Old September 26th, 2008, 08:51 AM   #10
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Please let me know when the cranial plug in becomes available. :)

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Old September 26th, 2008, 10:50 AM   #11
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Ty, I love to learn so just purchased your book. :)
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Old September 26th, 2008, 07:03 PM   #12
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Quote:
Originally Posted by Ty Ford View Post
I'm pretty sure it's in the manual.

Regards,

Ty
Ty, but not like Petri wrote it. Anyone new at this should print that out to keep handy when first getting to know their 302.

At the risk of embarrassing him, anyone who writes stuff in a forum like, "the tape took it gracefully" and "the lone jumping led showing the peak" while clearly explaining things, deserves attention. Don't ya love it?

Cheers.
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Old October 1st, 2008, 08:27 AM   #13
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I'm following the advice in this thread, level averaging around 0 and peaking just below +20.

But to reach this level I have to turn the gross gain knob all the way to +60 and have the fine gain around 2 o'clock. Are these settings "normal," as I hear significant hiss?

I'm using a Sanken COS-11xbp with phantom power.

Sanken | COS-11XBP Omnidirectional Lavalier | COS-11XBP-BK | B&H

I don't have a battery installed, but with phantom power I don't think I'm supposed to. I've also noticed that when I move the phantom power setting from 48v to 12v, there seems to be slightly less hiss. The mic is rated for 12v to 52v.

Have you all noticed that 12v can lead to less noise than 48v?

Thanks MUCH for the help!
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Old October 1st, 2008, 09:29 AM   #14
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Quote:
Originally Posted by Peter Moretti View Post
I'm following the advice in this thread, level averaging around 0 and peaking just below +20.

But to reach this level I have to turn the gross gain knob all the way to +60 and have the fine gain around 2 o'clock. Are these settings "normal," as I hear significant hiss?

I'm using a Sanken COS-11xbp with phantom power.

Sanken | COS-11XBP Omnidirectional Lavalier | COS-11XBP-BK | B&H

I don't have a battery installed, but with phantom power I don't think I'm supposed to. I've also noticed that when I move the phantom power setting from 48v to 12v, there seems to be slightly less hiss. The mic is rated for 12v to 52v.

Have you all noticed that 12v can lead to less noise than 48v?

Thanks MUCH for the help!
That seems to be a lot of gain required for a normal signal level. Are you sure the input sensitivity on the 302 is set to mic, not line?. Set the meter to VU mode. Set the channel fader to 0, mid-scale. Speak into the mic. You should be able to get the signal to hover around in the orange without having to turn the trim all the way up.
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Last edited by Steve House; October 1st, 2008 at 10:46 AM.
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Old October 1st, 2008, 10:37 AM   #15
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Also, try another mic and see if you still have the problem to make sure there's not a problem with the mic your using.

Also, the reason I bought the 302 was because at full gain on the mixer, there wasn't any noise from the mixer. (I needed this for a dynamic mic I had.)

If another mic causes the same problems and the sensitivity is set right on the 302's inputs, call Sound Devices. They are very helpful.
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