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Author Topic: What is above Zero DB in a DAW?  (Read 8300 times)

1DonM

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What is above Zero DB in a DAW?
« on: August 13, 2005, 07:02:27 am »

All:

I apolgize in advance for asking how much does 2+2 equal, but here goes....

I use several DAW tools of which one is Sonar 4.03 - Until recently I thought I understood 0db (Full Scale right?) Until some experiments in Sonar are allowing me to redline past 0DB and hit near +6Db - Can anyone explain what above 0 DB (again full scale right?) means - how is this mathematically possible? Ok, I'll keep saying it 2 plus 2 equals four....

Remember there are only 10 types of people in the world - Those who understand binary and those who don't.


Thanks in advance
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Barry Hufker

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Re: What is above Zero DB in a DAW?
« Reply #1 on: August 13, 2005, 07:59:42 am »

This is my guess.  And it is only a guess as I am not familiar with the DAW you're using.  I use Nuendo and I am basing my answer to you on that software.

If you have a 24 bit file, then that is its final bit depth when the file is stored.  But when working in Nuendo, all is processed using "32 bit floating."  You need more bits than 24 for increasing level, adding EQ. etc.  If your file is maxed out at 24 bits how could you increase the gain of an entire mix without more bits?  So, it is the increased number of "processing" bits that allow you to change your audio and extend its audio level past "0," as there is a much higher "0" with the processing bits.  The bits are truncated or re-dithered to 24 when you export your audio from the program you're using.

Now, if I have this wrong, a much smarter person will inform you (us) better!

Barry
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Bob Olhsson

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Re: What is above Zero DB in a DAW?
« Reply #2 on: August 13, 2005, 09:20:27 am »

Floating point lets you scale volume changes but it doesn't add resolution.

It's also real important to never assume all DSP processes have headroom in a floating point environment. Some do and some don't. Everybody should explore their applications and plug-ins with tones to learn exactly what each can and can't do level-wise. The digital world isn't nearly as different from the analog as many assume. It's just that overloads can cause a lot more harm to the signal.

Johnny B

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Re: What is above Zero DB in a DAW?
« Reply #3 on: August 13, 2005, 10:17:26 am »



What is above Zero DB in a DAW?

Bob's answer seems to be appropriate.

Some people might add that only "Clipping" is above 0db in a DAW resulting in very nasty digital distortion. For the same reason, many would say the technical definition of a DAW should be spelled out to say that "Digital Has Zero Headroom" in this respect and is one of digital's major drawbacks when compared to analogue.

Thus under this strict analysis, only Analogue has "headroom." while Digital has none.

,



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Paul Frindle

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Re: What is above Zero DB in a DAW?
« Reply #4 on: August 13, 2005, 10:56:20 am »

Johnny B wrote on Sat, 13 August 2005 15:17



What is above Zero DB in a DAW?

Bob's answer seems to be appropriate.

Some people might add that only "Clipping" is above 0db in a DAW resulting in very nasty digital distortion. For the same reason, many would say the technical definition of a DAW should be spelled out to say that "Digital Has Zero Headroom" in this respect and is one of digital's major drawbacks when compared to analogue.

Thus under this strict analysis, only Analogue has "headroom." while Digital has none.

,






The definition of headroom is the difference between your chosen target operating level and max allowable level at which is craps out. You can have any headroom you would like simply by aiming at a lower target level - you decide - it has nothing to do with digital at all.

As for 'disadvantage of digital' there is none in this regard - other than people electing to modulate everything at flat out sample values.

The 'headroom' we used to use in analogue was the difference between optimum target level and allowable extra level one could use judiciously - at variously reduced and variably unpredictable performance quality loss - somewhat before it crapped out big time.

Digital has no such uncertain disadvantage Smile
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compasspnt

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Re: What is above Zero DB in a DAW?
« Reply #5 on: August 13, 2005, 04:57:57 pm »

So keep those digital levels down, and you may have something akin to "headroom," not to mention a better overall sound.  I like -10 to -12.
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zmix

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Re: What is above Zero DB in a DAW?
« Reply #6 on: August 13, 2005, 06:46:41 pm »

He's not asking about interface headroom, he's asking about internal 'floating point' headroom. It's nearly impossible to exceed the internal headroom of a 32 bit floating point mixer - and the output can ultimately be scaled back to fit into a 24 bit word.

It's a remarkable thing but totally alien from an analog perspective - it's as if there were no difference between a global fader trim and turning down the makeup gain of the bus compressor...

maxim

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Re: What is above Zero DB in a DAW?
« Reply #7 on: August 13, 2005, 11:49:40 pm »

terry wrote:

"So keep those digital levels down, and you may have something akin to "headroom," not to mention a better overall sound. I like -10 to -12. "

that allows a transient or two to sneak through

what are your rms levels at the end of the mix?

do you bring up the volume in mastering?
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1DonM

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Re: What is above Zero DB in a DAW?
« Reply #8 on: August 14, 2005, 11:36:06 am »

Anyway I thought I keep this thread alive one more post with this thought...

All:

I love math threads so here goes another take on this...

1k sine wave @ -6db 24bit / 44.1k (5 seconds long) open Sound Forge 8.0b and mix paste at unity that file on top of itself once and -6 plus -6 goes to 0db redline in Sound Forge do another paste and Sound Forge's peak meters sit at 0db full scale / Now don't tell me Sound Forge doesn't operate in 32bit float. My current meter setting in Sound Forge are -18 (EBU Broadcast 0 VU (+4dBu).

Now....

1k sine wave @ -6db 24bit / 44.1k (5 seconds long) open Sonar 4.0.3 / copy that wave to four tracks lined up at 00:00:00:00 Send all tracks to a bus called master. Solo track one -6 on track meter and -6 on Master bus / Solo track on AND track two Master bus hits 0 db / Solo Track one, Track two and Track three, Master bus hits +3.5 and so on and so on

Now..
Here's the point - as in most things everybody has a point or an opinion right - but this is math / I try not to have an opinion about how much 2 plus 2 is!!!!

The only downside to me is I feel like doing currency exchange between software metering is annoying - I almost want the equivalent of the Mackie Big Knob (or whatever it's called) to sit at the absolute tail end of my DAW so all software is metered on the same scale. Thanks


comments...
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danickstr

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Re: What is above Zero DB in a DAW?
« Reply #9 on: August 14, 2005, 12:35:47 pm »

absolute 0dB in digital is all 1's in the number I thought.  but the scales go above I know, so I don't know if they use db watts or db volts.  
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Ronny

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Re: What is above Zero DB in a DAW?
« Reply #10 on: August 14, 2005, 02:17:09 pm »

1DonM wrote on Sun, 14 August 2005 11:36

Anyway I thought I keep this thread alive one more post with this thought...

All:

I love math threads so here goes another take on this...

1k sine wave @ -6db 24bit / 44.1k (5 seconds long) open Sound Forge 8.0b and mix paste at unity that file on top of itself once and -6 plus -6 goes to 0db redline in Sound Forge do another paste and Sound Forge's peak meters sit at 0db full scale / Now don't tell me Sound Forge doesn't operate in 32bit float. My current meter setting in Sound Forge are -18 (EBU Broadcast 0 VU (+4dBu).

Now....

1k sine wave @ -6db 24bit / 44.1k (5 seconds long) open Sonar 4.0.3 / copy that wave to four tracks lined up at 00:00:00:00 Send all tracks to a bus called master. Solo track one -6 on track meter and -6 on Master bus / Solo track on AND track two Master bus hits 0 db / Solo Track one, Track two and Track three, Master bus hits +3.5 and so on and so on

Now..
Here's the point - as in most things everybody has a point or an opinion right - but this is math / I try not to have an opinion about how much 2 plus 2 is!!!!

The only downside to me is I feel like doing currency exchange between software metering is annoying - I almost want the equivalent of the Mackie Big Knob (or whatever it's called) to sit at the absolute tail end of my DAW so all software is metered on the same scale. Thanks


comments...



Sure, I'll comment. Your increase in gain is due to bus summing. Anytime that you double a buss you increase gain by +6dB. You can have all multi-tracks below -0dB and the sum of those tracks can be well above -0dB. Because 32 bit float is scaled you can turn the master section down by amount of dB's that the summed tracks accumulate and still not clip the DAC's output. It's the reconstructed waveform that you have to be concerned about with clipping, not the processed form while in float. You can indeed process above -0dBFs in a 32 float system, but you must attenuate it somewhere before the DAC, the master section is an ideal place to do this as it's the last stage before the reconstruction. Ideally you would want to attenuate the input of any processor by the amount of output that is boosted, but it's not really necessary in a 32 float system as long as the signal does not exceed -0dBFS at the DAC.

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compasspnt

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Re: What is above Zero DB in a DAW?
« Reply #11 on: August 14, 2005, 08:59:02 pm »

maxim wrote on Sat, 13 August 2005 23:49

terry wrote:

"So keep those digital levels down, and you may have something akin to "headroom," not to mention a better overall sound. I like -10 to -12. "

that allows a transient or two to sneak through

what are your rms levels at the end of the mix?

do you bring up the volume in mastering?


mixing for me will almost always be through an analogue console, in most cases track-for-track out, if in a daw...so rms levels for mix will come back about the same, -10-ish.  maybe -6 peaks.

yes, bring the volume up in mastering...
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tom eaton

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Re: What is above Zero DB in a DAW?
« Reply #12 on: August 15, 2005, 08:12:11 am »

I've been much happier with things here since I started using -20dBFS as my 0VU/+4 level.  Tons of actual headroom (as Paul stated) and less work for the electronics getting the signal post computer.

-tom

thedoc

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Re: What is above Zero DB in a DAW?
« Reply #13 on: August 15, 2005, 09:21:35 am »

Yes, -20 for 0VU works quite well and is also good for post sound.
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Barry Hufker

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Re: What is above Zero DB in a DAW?
« Reply #14 on: August 15, 2005, 11:23:55 am »

OK, here's *my* math problem -- if a train leaves Boston at 60 miles per hour and a second train...

I do want to re-emphasize the earlier point.  While 32floating would be tough to overload (someone said "impossible"), individual plugins can be easily overloaded and as was said, one should check carefully to see which those are.

Barry
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