-18db digital = 0db analog

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GillyDJ
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-18db digital = 0db analog

Post by GillyDJ » Wed Feb 22, 2012 2:20 pm

I've recently read things about -18db digital being equal to 0db analogue (practically at least, not sure about theoretically).

Basically, you are supposed to receive better results with your final mix if you do not allow any track to PEAK over -18db. Obviously the track's volume slider may not be at -18db depending on the source audio or midi instrument + effects but the peak must not be over -18db.

As most people start mixing with and around the kick I would assume the kick must be punching at -18db.

I assume the tracks will add up at the group, then the groups will add up at the master, giving you a master output volume way below 0db and hopefully something nearer to -3db to -6db ready for professional mastering.

Using this method also means your plug-ins are not supposed to be worked as hard giving you cleaner results.

Has anyone else heard of this theory and whether it actually results in a better mix? Some producers swear by it (some have a -14db theory as apparently analogue is between -10db and -18db and this is halfway inbetween).

chapelier fou
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Re: -18db digital = 0db analog

Post by chapelier fou » Wed Feb 22, 2012 2:28 pm

this all sounds like nonsense to me...
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GillyDJ
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Re: -18db digital = 0db analog

Post by GillyDJ » Wed Feb 22, 2012 2:38 pm

Some very successful and famous producers saying it!

Rationalizer
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Re: -18db digital = 0db analog

Post by Rationalizer » Wed Feb 22, 2012 2:46 pm

GillyDJ wrote:Some very successful and famous producers saying it!
Was it the same one who said that Live sounds like crap and Nuendo sounds great?
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Angstrom
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Re: -18db digital = 0db analog

Post by Angstrom » Wed Feb 22, 2012 3:15 pm

I would imagine that most of these users you mention were commenting on their ProToolsHD workflow, where per-track-output hovering around 0db is a very bad thing. ProTools HD has historically used a fixed-point internal mixing system, that means that anything above 0db on a channel output is going to start clipping. They have added 32 bit float recently.

Most other applications (such as Live) use floating point calculations, floating point has a vast headroom and this means you can (accidentally) exceed 0db by quite some margin and then turn it back down again later in signal the chain with no real detriment (in most cases). Obviously don't clip the master though!

If you want to know how floating point numbers work the internet has a variety of explanations.

fx23
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Re: -18db digital = 0db analog

Post by fx23 » Wed Feb 22, 2012 3:35 pm

this is stupid imo since there are no correlation between digital volume and analog, the output analog signal depends of output preamps gain wich vary from one soundcard to another.

In live as said you can go far in the headroom exept for master, but some VST won't accept >0 db input signals so it's a good practice to stay below imo

Warrior Bob
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Re: -18db digital = 0db analog

Post by Warrior Bob » Wed Feb 22, 2012 3:43 pm

GillyDJ wrote:Some very successful and famous producers saying it!
Do you have a link handy? This doesn't sounds quite right. I don't see how your plugins could be 'worked less hard' with a lower leveled signal. It does not require more power for a software algorithm to produce a higher number.

That said, when composing and doing early mixing I personally like to drop the track faders way down (-18dB sounds about right), and turn up my monitors, but I do this to enjoy the headroom rather than because it improves the mix somehow. I'm not entirely sure there's a difference between this and having the tracks higher but still not clipping.

Angstrom
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Re: -18db digital = 0db analog

Post by Angstrom » Wed Feb 22, 2012 3:50 pm

Warrior Bob wrote:
GillyDJ wrote:Some very successful and famous producers saying it!
Do you have a link handy? This doesn't sounds quite right. I don't see how your plugins could be 'worked less hard' with a lower leveled signal. It does not require more power for a software algorithm to produce a higher number.
I thought the same, but then wondered if it was meant as a figure of speech for 'not overdriving' , for example if we "work a reverb hard" we might be feeding it a signal peaking at 0db, which in some circumstances could be problematic. But yes, plugins don't get tired. ;)

Dean Corrie
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Re: -18db digital = 0db analog

Post by Dean Corrie » Wed Feb 22, 2012 4:32 pm

Hello,
All to do with dBFS, dBu, dBv, dBV etc.
Google is your friend.
Cheers,
Dean

synnack
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Re: -18db digital = 0db analog

Post by synnack » Wed Feb 22, 2012 6:03 pm

Angstrom wrote:I would imagine that most of these users you mention were commenting on their ProToolsHD workflow, where per-track-output hovering around 0db is a very bad thing. ProTools HD has historically used a fixed-point internal mixing system, that means that anything above 0db on a channel output is going to start clipping. They have added 32 bit float recently.

Most other applications (such as Live) use floating point calculations, floating point has a vast headroom and this means you can (accidentally) exceed 0db by quite some margin and then turn it back down again later in signal the chain with no real detriment (in most cases). Obviously don't clip the master though!

If you want to know how floating point numbers work the internet has a variety of explanations.
+ 1. 100% correct. Thread over. Unless a famous producer says another nugget of wisdom.
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ollyb303
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Re: -18db digital = 0db analog

Post by ollyb303 » Wed Feb 22, 2012 6:10 pm

Good job angstrom stepped in with some reality there.

Also kind of a shame - i'd have liked to see where this went...
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starfckr
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Re: -18db digital = 0db analog

Post by starfckr » Wed Feb 22, 2012 6:24 pm

This is all about proper gain staging, especially between the analog and the digital world.

Example:

Route a 1khz tone signal from live out to an external preamp (or another OTB-unit), out from the preamp, and into live again through your interface.
Open up the volume of the signal so the meter on the preamp says 0VU.

The signal coming in through the DAW should now peak at somewhere between 12-24 dbfs (full scale), depending on your preamp and interface.

If you now were to make the signal hotter in the analog world, so that it peaks at 0dbfs in live, you would be running well into the "red" in the digital world, destroying your signal.

I always try to record signals peaking at maximum 12 dbfs, both when dealing with analog and digital.
It also makes for better workflow, as while tracking everything, you dont have to constantly pull down faders.
When i have a song fully recorded, all faders should be at unity gain without clipping the master.

... Also, as some said. Google is your friend. There is a lot of information about proper gain staging out there.
Its a bit hard to grasp, but atleast it has improved my mixes alot.

If your all in the box though, why not track as hot as possible?
Well, a lot of plugins is also made so that they work "best" when input with a signal that is not always making the plugin works as hard as it can, if that makes sense.

Off coarse, i am no expert in this, but this is what i have grasped, and it works for me.
People that are only mixing in the analog realm are in fact mixing ALOT lower than most people in the digital realm.

sanfoin
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Re: -18db digital = 0db analog

Post by sanfoin » Thu Feb 23, 2012 12:51 am

surprising no one has really answered the original post without taking it too literally. of course the equation is false, but in audio tech isn't there an equation with -18 & 0? cut the guy some slack, it's not a stupid question.


it's potentially confusing, but -18db does = 0db if you're comparing two different scales, one dbFS and the other dbVU. it's good to know the difference!

here's a useful link to an explanation of this by a member of this forum (i forget his username). . .


http://www.massivemastering.com/blog/in ... Levels.php

shuutobi
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Re: -18db digital = 0db analog

Post by shuutobi » Thu Feb 23, 2012 1:09 am

Warning, the follow consists of gain stage information, digital reference level information, real world SPL level information, and digital mixing VU level information... It's a goulash!


The UK has a standardization of -18dBu = 0VU, so if you were to run an -18dBFS sine wave through live with the test tone with full output on your I/O to a UK made mixer/amp, it should read 0VU.(You can also just test with a volt meter to see if the output is 0.775V)

Now say you just want to make sure the I/O output isn't going to clip your active monitors. (Which is the setup for most of the digital only people)
You will need to find the maximum output of the I/O and the maximum input of the monitors. For example, My USBPre2 has a max output of +18dBu (For the balanced out) and my monitors have a max input sensitivity of around -4dBu IF the input control is all the way up. The input attenuation has a 20dB range so that puts my monitors max input at around +16dBu if all the way down. If I were to play a file on my computer that put the output to a constant 6.15V, and my input sensitivity on my monitors were all the way down, it would clip and/or likely kill my monitors.

I do have my input sensitivity turned all the way down for 2 reasons unrelated. A) The tweeters are noisy if I don't, and B) the input knobs are not detented so I can't get them match accurately. What's more important is that after you have made sure the output level of your I/O correlates with your reference standard, is that when/if you're mastering, is that your real world level is the same. Run some pink noise or a sine wave @ -12dBFS, -18dBFS, or -20dBFS whatever you've chosen as your standard (depends on the medium) though your monitors and check with with an SPL meter to see if it's hitting 85dB SPL(c-weighted). Mark this level on your physical output knob if you have one for quick recall.

You don't have to mix at this level, so just find whatever is comfortable and keep it consistent.

p.s. An in the box digital note: Use PSP vintagemeter and setup it up to 300ms RMS and whatever reference level you're using (for mixing with "VU") -or- 600ms and whatever reference level you're using (-20dB RMS, -14dB RMS, -12dB RMS) for the k-system, for mastering. If mixing, place one of these on your master channel, changes the settings accordingly on the back, set to VU, and solo your kick or snare. Make your kick and snare hit around 0VU, and your hats hit around -12 to -6VU, Bass around -1 to +1. Now mix everything around that. Don't worry about the peaks. (Just suggestions)
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fx23
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Re: -18db digital = 0db analog

Post by fx23 » Thu Feb 23, 2012 5:14 am

@sanfoin: the 18 db / 0 thing has nothing to come into equation in this case as music is made digitally internally, there is no analog gear that suffer or has to turn at nominal level involved,

so the only rule is avoid digital clipping. afaik it's a good practice to keep headroom for plugins to not saturate, but there are absolutely no use to focus on -18db thing when using live, that

's just why i said it was stupid, cause it's certainly not a rule that will make your music better in digital domain. of course there are no stupid questions, thanks for the smarter explain ;)

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