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Old 05-24-2019, 07:19 PM   #1
talustalus
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Default Recording levels into preamp, the -18dBFS myth?

Hi

I have read from various sources that when recording into outboard preamp gear, you should aim to get the level around -18dBFS based on the VU metering system of yesteryear (where, -18dBFS = 0dBVU).

I wonder what people here's thoughts on this are?

I'm trying to record vocals and I have to turn up my mic preamp gain trim way high to get my singing level to be around -18dBFS on average. The downside is that with the trim set high, I can hear the noise floor and it's off-putting.

I don't see why I can't just record quieter and then raise the level of the audio after the fact? -- I mean, I know I can do this, but is there any engineering reason why I should not?

Thanks.
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Old 05-24-2019, 07:57 PM   #2
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If you are getting better results recording low and then raising it later, then go for it.

The -18dbFS things is not a rule, just a good guideline to give folks enough headroom. It's to teach people to not go too hot into the recorder because 0dbFS will sound really horrible and there's no recovering from that. So play it a bit safer and aim for lower.

The only issue going very low, like peaking around -30dbFS, is you may start to notice a lack of resolution or precision in the audio, and you can introduce additional noise from the noise floor of your recording chain. For this reason 24-bit recording is a bit better off, because typically at that bit depth the converters are less noisey along with of course giving more resolution.

But again, if you found the best way to get clean audio with minimal noise, then that's obviously your best choice.
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Old 05-24-2019, 08:03 PM   #3
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If you know ahead of time what the absolute highest level hitting your preamp will be, you can simply set a level to not hit 0 or go over.

If you don't know that ahead of time - because you are recording something new and aren't clairvoyant - shooting for -18 should keep you distortion free even if a few surprises come along.

That's the main point. An rms target level that should result in the loudest peaks not going over.

You seem to be having the opposite problem! So... no problem at all (with clipping peaks)!
Curious. You singing into an SM-7 or something?
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Old 05-24-2019, 09:23 PM   #4
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Quote:
Originally Posted by Tomm View Post
If you are getting better results recording low and then raising it later, then go for it.

The -18dbFS things is not a rule, just a good guideline to give folks enough headroom. It's to teach people to not go too hot into the recorder because 0dbFS will sound really horrible and there's no recovering from that. So play it a bit safer and aim for lower.

The only issue going very low, like peaking around -30dbFS, is you may start to notice a lack of resolution or precision in the audio, and you can introduce additional noise from the noise floor of your recording chain. For this reason 24-bit recording is a bit better off, because typically at that bit depth the converters are less noisey along with of course giving more resolution.

But again, if you found the best way to get clean audio with minimal noise, then that's obviously your best choice.
Thx. Are you saying 24-bit recording maintains resolution even at low input signal recording?
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Old 05-24-2019, 09:25 PM   #5
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If you know ahead of time what the absolute highest level hitting your preamp will be, you can simply set a level to not hit 0 or go over.

If you don't know that ahead of time - because you are recording something new and aren't clairvoyant - shooting for -18 should keep you distortion free even if a few surprises come along.

That's the main point. An rms target level that should result in the loudest peaks not going over.

You seem to be having the opposite problem! So... no problem at all (with clipping peaks)!
Curious. You singing into an SM-7 or something?
Thx. Yeah, I guess another part to my question is -- how much noise floor being audible is acceptable? Maybe a little is normal, because I'm sure it won't stick out in a mix (it's at like -66dBFS), and could be treated in mixing anyway.

I am using an SM7B in this example.
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Old 05-24-2019, 09:45 PM   #6
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Yeah, the SM7 has a low output. People with loud obnoxious voices that can pummel other mics like it.

If you were singing all quiet and delicate like, maybe noise could creep into the mix. But you're probably fine.

24 bit makes lots of things easy yes.
You could turn a source down 96db and still have 8 bits of resolution left!
Makes it easy to record and not worry about getting digitally grainy at low levels. As the consumer format, it delivers full fidelity and nuance no matter how dynamic your final master is.
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Old 05-24-2019, 09:57 PM   #7
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Originally Posted by talustalus View Post
Thx. Are you saying 24-bit recording maintains resolution even at low input signal recording?
it maintains MORE resolution, sure



Imagine recording a sine wave at a low level in both 16 and 24-bit. the 24-bit version will be more accurate because there are more "steps" to represent the shape

Quote:
how much noise floor being audible is acceptable
That's up to you, but what you should be concerned with is noise-to-signal ratio.



if you move the example on the right up or down (raise and lower the gain) it won't really make a difference because the signal-to-ratio will be the same, you would just be raising and lowering both the noise and signal, and when mixing it'll end up being about the same anyways.

what isn't shown in this graphic is there are other things that contribute to the noise, like that preamp maybe gets noisier at higher gain settings making the signal-to-noise ratio lessened. so you can't just use numbers and meters to figure this stuff out, you gotta experiment.

The SM7B needs a lot of gain on most voices, so the preamp needs to be pretty high quality. or try to sing louder or closer to it to raise the signal-to-noise ratio.
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Old 05-24-2019, 10:31 PM   #8
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-18 db means loosing 3 Bits, which is no problem with a 24 dB A/D converter. (Regaring that the resolution of a CD is 16 bits, and analogue Studio tape provides an equivalent of something like 14 Bits.)

hitting the digital limit at 0dB is a catastrophe..

Hence -18 dB is not a myth, but a compromise that seems useful in many situations.

Of course using an analogue compressor before the A/D converter allows for reducing the digital Headroom appropriately.

-Michael
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Old 05-25-2019, 12:08 AM   #9
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get a cloud lifter - or another brand.
This will get you more gain from the mic into your pre amp and will help.

Most people don't realize that the majority of budget gear has 10cents worth of parts in the mic pre - therefore they sound crappy when gained up.

If you are really into the sound of the (very low level) SM7B - then best to invest in a good preamp to get plenty of clean gain, and then after the mic preamp - go line in to your A to D convertor.

Found this on 1st search for cloudlifter!

https://www.youtube.com/watch?v=dfDPD3_3128

There is no -18dbFS myth - you have a very low level mic, and you also must have a mic pre that is not suitable for low level mics.

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Old 05-25-2019, 09:07 AM   #10
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Remember that the -18 target is rms.

No one is suggesting that the loudest peak should be at -18db.
If the average level is -18db, any loud peak that comes along can go up to 0db but will usually not clip. It's still a guess! You still might clip with a hot surprise! It's simply a good starting point if you don't know how hot the peaks might get.

It's not really fair to even think about it like a compromise either. Like "sacrificing 3 bits of resolution". It's literally using the dynamic range of the recording device properly.
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Old 05-25-2019, 09:42 AM   #11
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Quote:
I wonder what people here's thoughts on this are?
Since digital cannot exceed zero and analog can, the digital scale is "pushed down" comparatively to allow room for the analog gear to go beyond zero without exceeding the zero dBFS limit in digital. This means that if your analog gear is set to roughly unity gain. 0dbVU, it will appear somewhere around -18dbFS RMS(give or take a couple of dB depending on the sound card manufacturer).

The myth part is that once in the box, or if it was always in the box (such as VSTs or samples) that there is some sonic magic to being at -18 dBFS RMS but there is none, ignore that and just remember that unity gain in analog lives somewhere roughly around 18 dBFS RMS in the box. Note that I keep mentioning -18 dBFS RMS because that's important.

Quote:
I'm trying to record vocals and I have to turn up my mic preamp gain trim way high to get my singing level to be around -18dBFS on average. The downside is that with the trim set high, I can hear the noise floor and it's off-putting.
Then your mic doesn't have enough output and you are having to push the preamp to get the level even up to "zero" in analog, it is unrelated to digital, as in if this were a pure analog environment you'd be saying "wow, I really had to crank the preamp on this mic to get a decent level on my analog board"

The Cloud Lifter idea is OK (I have one) but it's only going to help if it's gain is cleaner than pushing your existing preamp hard, cuz there is no magic in audio.
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Old 05-25-2019, 09:48 AM   #12
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Originally Posted by ChristopherT View Post
There is no -18dbFS myth
Just for clarity there is one myth (which I hope has pretty much died out by now), there's a super long thread over on GS about it if memory serves and it has to do with people thinking their mixes are magically better if they manually set all their item levels to -18 dbFS RMS which is a complete myth. Obviously, there is a benefit if one is organized with their levels which results in less work and ultimately a less messy way to get to the result but there is no sonic magic going on.

The idea that a sound card manufacturer has to leave some wiggle room for audio gear is not a myth, it's just common sense. IOW, if they made zero dBVU = 0dBFS RMS then as soon as your analog gear went over 0 dBVU you'd be clipping in the DAW which would be silly and a bad design. So what do they do? They offset the two "zeros" with enough distance to handle the average amount analog gear can exceed 0 dBVU.
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Old 05-25-2019, 04:27 PM   #13
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No one is suggesting that the loudest peak should be at -18db.
Actually that IS the suggestion. Practice the loudest part of the performance, PEAK at -18dbFS, record at 24-bit.

Getting into RMS is just asking for trouble and is really not necessary.
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Old 05-25-2019, 04:41 PM   #14
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Actually that IS the suggestion. Practice the loudest part of the performance, PEAK at -18dbFS, record at 24-bit.

Getting into RMS is just asking for trouble and is really not necessary.
I don't disagree agree with being conservative but if you run your analog gear in it's nominal range, you'd have to peak it beyond +18 dB analog to peak in the DAW above zero. Meaning, one should be able to sanely record at -18 dbFS RMS in most cases, until you get "that guy" on snare and so on. So with 0 dBVU being *roughly* the same as -18dB FS RMS, it's hard to call that not necessary. Again, no problem with being conservative but calling it unnecessary isn't quite right for what is actually the nominal range.

Beyond that, many do conflate -18dBFS RMS with -18dBFS but where sound card references are concerned it's dBFS RMS.
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Old 05-25-2019, 04:44 PM   #15
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of course Kenny G has a great tutorial on this:


...and note the meters are not showing RMS values but PEAKS, he's just going for an average peak at around -18 (but no greater than -12). It's just a simpler technique for newbies than breaking out all this RMS stuff, which of course can be vastly different depending on the source and meters you are using.

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Old 05-25-2019, 04:51 PM   #16
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Originally Posted by karbomusic View Post
The Cloud Lifter idea is OK (I have one) but it's only going to help if it's gain is cleaner than pushing your existing preamp hard, cuz there is no magic in audio.
Which is a legit way of overcoming a real issue, which is that it's common of the top 20% of a preamp's input gain to be noisier (due to the preamp's design) and also sound different, possibly less attractive (same) than at 40 - 80%. Though it doesn't change the noise floor regarding anything else (room, other gear noise) I find that using a clean inline preamp booster to be a huge benefit for low or even low-ish output mics in getting a cleaner result than without.

I used to get around it be not using low output mics (before inline boosters were available). But around the time I realized all the guitar pickups I favored were low output and I actually never met a high output pickup I much liked (and I hated most), I realized that was a dumb approach. I was missing out on some low output mics, like the SM7, that I'd really like using if I at least had a pre that could present it well. For a long time I only had two channels (ULN2) that could. Cloud Lifters made a big difference for me in that I could employ certain mic/preamp combinations that I couldn't before, and for much less than getting a few more clean higher gain pre channels. I guess I'm just more enthusiastic about them for that one pony trick they do. And of my favorite mics now pretty much none are very high output ones. High output mics sort of became my super overwound hot hot output pickup. In the drawer
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Old 05-25-2019, 04:53 PM   #17
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Quote:
Originally Posted by Tomm View Post
of course Kenny G has a great tutorial on this:


...and note the meters are not showing RMS values but PEAKS, he's just going for an average peak at around -18 (but no greater than -12). It's just a simpler technique for newbies than breaking out all this RMS stuff, which of course can be vastly different depending on the source and meters you are using.
Yes, that' his newbie how do you set levels video and it's main message is don't clip the converters. And "average peak" is an interesting choice of words. However, think of what RMS is and then which instruments would easily exceed that by 18 dB SPL when playing them. I'm not saying you should go for -18 dbFS RMS, I'm saying that if you use your gear within it's prescripted range, most things will take care of themselves.
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Old 05-25-2019, 04:56 PM   #18
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Which is a legit way of overcoming a real issue, which is that it's common of the top 20% of a preamp's input gain to be noisier (due to the preamp's design) and also sound different, possibly less attractive (same) than at 40 - 80%. Though it doesn't change the noise floor regarding anything else (room, other gear noise) I find that using a clean inline preamp booster to be a huge benefit for low or even low-ish output mics in getting a cleaner result than without.

I used to get around it be not using low output mics (before inline boosters were available). But around the time I realized all the guitar pickups I favored were low output and I actually never met a high output pickup I much liked (and I hated most), I realized that was a dumb approach. I was missing out on some low output mics, like the SM7, that I'd really like using if I at least had a pre that could present it well. For a long time I only had two channels (ULN2) that could. Cloud Lifters made a big difference for me in that I could employ certain mic/preamp combinations that I couldn't before, and for much less than getting a few more clean higher gain pre channels. I guess I'm just more enthusiastic about them for that one pony trick they do. And of my favorite mics now pretty much none are very high output ones. High output mics sort of became my super overwound hot hot output pickup. In the drawer
It kind of works both ways, a lot of good preamps sound better when running a little hot so the OP should listen and forget about what the meters say in that instance. I have mostly nice pre's and my CL almost never gets used because it simply isn't needed. The lesser the pre (not magic, just lesser) and mics that have low enough output, and recording a source that's also not loud enough to make up the difference, the more use the CL might be. It may be more prevalent with small pre's jammed up close to other stuff like converters etc, so not knocking it, but it's not really a panacea either.
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Old 05-25-2019, 05:09 PM   #19
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It kind of works both ways, a lot of good preamps sound better when running a little hot so the OP should listen and forget about what the meters say in that instance. I have mostly nice pre's and my CL almost never gets used because it simply isn't needed. The lesser the pre (not magic, just lesser) and mics that have low enough output, and recording a source that's also not loud enough to make up the difference, the more use the CL might be. It may be more prevalent with small pre's jammed up close to other stuff like converters etc, so not knocking it, but it's not really a panacea either.
Yup. Agree all around.
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Old 05-25-2019, 05:13 PM   #20
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"average peak" is an interesting choice of words.
That's on Kenny, not me but also that's how the OP described it, so I assume that's what he meant, and not RMS levels
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Old 05-25-2019, 05:40 PM   #21
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That's on Kenny, not me but also that's how the OP described it, so I assume that's what he meant, and not RMS levels
I couldn't help myself.
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Old 05-25-2019, 06:19 PM   #22
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Makes sense that the reason is a low output mic such as the SM7B. When you consider that a staple use for this mic is putting it in front of a guitar amp speaker, it makes even more sense.
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Old 05-25-2019, 06:35 PM   #23
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it maintains MORE resolution, sure
This is utter bullshit.

-18dbFS is not really a myth, but it's not necessarily true that 0dbVU (= +4dbu) = -18dbFS for any given interface. You have to read and decipher your specs, and sometimes that means doing math.

The right thing for the OP to do is figure out where on the interface gain knob they get the best S/N ratio. Turning it up to where your signal averages -18dbFS gives you a certain measurable noise floor. Does averaging -30dbFS put the noise floor further below your signal? If you normalize them to the same average, which one has less noise. That's all that matters. Period.
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Old 05-25-2019, 07:34 PM   #24
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This is utter bullshit.
what's bullshit? I think we're all in agreement that S/N is the most important thing, 24-bit just gives you more room to place your recording level as it offers more resolution and thus a lower theoretical noise floor than 16-bit
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Old 05-25-2019, 07:44 PM   #25
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I dunno if this helps, but it's another way of looking at things... anyone disagree with it?

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Old 05-25-2019, 07:45 PM   #26
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Does averaging -30dbFS put the noise floor further below your signal? If you normalize them to the same average, which one has less noise. That's all that matters. Period.

This is a good test. I will do that.
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Old 05-25-2019, 08:42 PM   #27
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I dunno if this helps, but it's another way of looking at things... anyone disagree with it?

I disagree that any of this matters for the average person recording at home. Keep your recorded peaks well below 0 dBFS so that you aren't having to think about possibly going over. I have compared recorded tracks near 0 dBFS (for testing) and well below (including -18 dBFS), and I didn't hear any notable differences with my gear. I say to be practical about it. Think about where the track level will end up being in a mix. Try and record at that level.

And if your preamps are noisy at higher gain settings, obviously try and avoid that. But that can be a bit of foolery, because as you turn your preamps up, you are going to hear an overall louder signal including a louder noise level. But signal to noise is relative, no matter how loud you are hearing the incoming signal. So if you think it matters for your preamps, do some comparing by recording at lower and higher preamp gain settings and then matching the levels of the recorded tracks to have a listen. Maybe it is the case that any difference doesn't matter at all to you for your situation and gear.

Any way, I think that 'rules' tend to get people thinking the wrong way about things. What is practical? What problems do you hear, if any? How can you do direct comparisons? That should guide you, not 'rules'.
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Old 05-25-2019, 09:55 PM   #28
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a lot of good preamps sound better when running a little hot so, the OP should listen and forget about what the meters say in that instance.
When using a (e.g. tube-) preamp to create some "color" by driving it "hot", this is dedicated analogue processing. If doing so, you need to use an output control of the preamp to perfectly avoid coming close to 0 dB with the A/D converter. And here the -18dB rule - after the preamp - as Kenny describes in the video, still applies. And Kenny in fact describes "average peak": using peak measuring and make sure that by far most of the peaks you see stay around -18 dB.

-Michael

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Old 05-25-2019, 10:10 PM   #29
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what's bullshit? I think we're all in agreement that S/N is the most important thing,
Avoiding digital distortion obviously is even more important.

If you have a signal that is very soft - but important - most of the time but very loud in some places (think of an ambiance scene with talking people, and sometimes somebody shouts out near the mic), you might need to intentionally tolerate some technical noise floor in favor of not being hit by digital distortion. Here only a (very good) analogue compressor (together with a very good mic and a very good preamp) will help.

-Michael
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Old 05-25-2019, 10:49 PM   #30
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ah, good S/N implies you have healthy headroom and aren't clipping the AD (because that would technically be less s/n), but yea you are right and I was over-simplifying a bit with that statement :P

for the preamp color discussion, don't forget about attenuation adapters for those who don't have output gain knobbies... something magical happens driving APIs into the red for rock drums/guitars and throwing a few of these on the outputs

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Old 05-25-2019, 11:15 PM   #31
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When using a (e.g. tube-) preamp to create some "color" by driving it "hot", this is dedicated analogue processing. If doing so, you need to use an output control of the preamp....
True but I'm not discussing -18dB or digital in the sentence you quoted FWIW. On second thought though, if the mic is low output, the pre isn't actually running hot, it's just potentially noisier from having to crank it, making the entire run hot/output knob part irrelevant anyway.

Kenny's video IIRC is a no-nonsense method for beginners to get usable levels which is perfectly good; there is no -18dbFS peak rule but there is a -18dbFS RMS result (or whatever that reference value is on your sound card). My RME is actually -19 dB FS RMS if memory serves for example - but I never actually use any of these numbers, I just set the damn gain on my pre and make sure it doesn't clip.
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Old 05-26-2019, 01:53 AM   #32
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-18dBFS myth.
I heard it's to do with gain staging and also that plugins are tested optimally for -18dBFS input.
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Old 05-26-2019, 02:20 AM   #33
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AFAIU (and regarding Kennie's Video) the -18dB Rule is only applicable at the point of the A/D conversion.

"gain staging" IMHO in fact (in most cases) is a myth in the realm of a DAW.

-Michael
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Old 05-26-2019, 03:41 AM   #34
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"gain staging" .... is a myth in the realm of a DAW.
It's not a myth.

"Gain staging is the process of managing the relative levels in each step of an audio signal flow to prevent introduction of noise and distortion. Ideal gain staging occurs when each component in an audio signal flow is receiving and transmitting signal in the optimum region of its dynamic range"

And here are about 38,700,000 articles about your 'myth':

https://www.google.com/search?source...10.8v7s5kyRGOk

If you still believe it's a myth, then record everything at 0dBfs then push your faders to +12dB on every track then tell us how great your master bus is sounding.

Equally, put a gain plugin before and after each plugin and boost by +24 then cut after it by -24. See how your music sounds.
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Old 05-26-2019, 03:43 AM   #35
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I heard it's to do with gain staging and also that plugins are tested optimally for -18dBFS input.
Some plugins. Mostly analog emulations like Klanghelm, waves or IK for exemple.
But for a lot of 'proudly' digital plugins it does'nt matter like Reacomp for instance as long as you don't peak the master output going to the interface you can be in the red all over the place on the channels.

Going into digital plugins you don't want to clip though it sounds like crap but as long as you don't peak, -18db or not, it sounds just the same IF it's digital and not meant to replicate saturation of analog beeing driven hotter.

Some analog emulations are meant to be going in the red though so rtfm on this.

Still the -18db rule is a decent workflow idea, where you keep your channel meters away from the red giving you a visual idea of the outcome, and keeping your signals ready to be sent into hardware or for a emulation plugin. This is why it's good practice to use the output button ,wich is pretty much a standard button on every plugin these days, to readjust to -18 going out of the plugin or use AGC ( automatic gain compensation ).

Read the manual for nominal(optimal) levels of each plugins.

Last edited by Pinknoise; 05-26-2019 at 04:09 AM.
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Old 05-26-2019, 03:47 AM   #36
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Originally Posted by Pinknoise View Post
Some plugins. Mostly analog emulations like Klanghelm, waves or IK for exemple.
But for a lot of 'proudly' digital plugins it does'nt matter like Reacomp for instance as long as you don't peak the master output going to the interface you can be in the red all over the place( not a practical workflow though ).

Read the manual for nominal levels of each plugins.

Pro-tip: Actually it's more productive and less time-consuming to simply assume -18 is the optimal level than to concern yourself with mental lists of which is or isn't.
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Old 05-26-2019, 04:16 AM   #37
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"Gain staging is the process of managing the relative levels in each step of an audio signal flow to prevent introduction of noise and distortion.
This is perfectly retro but plain wrong in a DAW. A DAW internally uses Floating point format for the samples and hence the absolute value of the numbers (i.e. the gain of the signal) is of absolutely no concern at all.

Of course it is true that there are cases where the signal gain does make a difference: at any A/D and D/A conversion (i.e. analogue outboad equipment) and certain "nonlinear" plugins that don't feature an input gain control setting (which I esteem erroneously crafted).

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record everything at 0dBfs then push your faders to +12dB on every track then tell us how great your master bus is sounding.
Say you have a setup that features no nonlinear plugins (e.g. just ReaEQ and ReaDelay). Say you have a ReaEQ followed by a ReaDely in any track and a ReaEQ in the master FX. everythging is running at about 0 dB. Now you increase the Gain slider in the ReEQs in all tracks by 12 db and decrease the Gain slider of the ReaEQ in the master by 12 dB. The meters near the Track sliders will look horrible but the resulting rendered file will be exactly the same.

(Reaper even might force a track to Mute for safety of your ears, but you can disable this feature in the preferences.)

Same is true when lowering the gain in the tracks by whatever dB and increase it in the master appropriately. The render result will be the same: no additional noise.

-Michael

Last edited by mschnell; 05-26-2019 at 05:59 AM.
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Old 05-26-2019, 05:29 AM   #38
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Makes sense that the reason is a low output mic such as the SM7B. When you consider that a staple use for this mic is putting it in front of a guitar amp speaker, it makes even more sense.
If you don't have a loud singing voice and/or aren't eating the mic, then you might be better served by a different microphone.
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Old 05-26-2019, 07:08 AM   #39
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It's not a myth.


Equally, put a gain plugin before and after each plugin and boost by +24 then cut after it by -24. See how your music sounds.
It will sound perfectly fine if the gain is linear using reapers defaults... Look ma' rendered @+34 dbFS and completely recoverable... Just so everyone is aware, I could have gone to about +1000dBFS and still been fine @32bit float. (Reapers internal default is 64 bit FYI).



I get what you are trying to say and agree but only to a point because specifics matter greatly and you are talking about several different things all at once.

As I hinted in one of my first posts, bad habits will cause fader chasing, and it's generally a bad workflow idea etc. but while in the DAW it is not damaging the audio unless it is a non-linear plugin. "How it sounds is" is irrelevant to ITB once it passes through the converters. So, I agree that the habit yields likely better results and less work but while in the DAW, it is not hurting the audio in the way the "old myth" thinks it is from an analog perspective, so it is very important that we separate exactly which "things" we want to talk about with gain staging. Because analog gain staging and changing levels in the DAW are NOT the same thing.

FWIW, your search term was just "gain staging" with zero regard to things like the above so of course you'll get millions of hits, you'll still get them by adding ITB and/or DAW but at least then, some good research will bear out what I'm saying, if you can get all the myth noise out of the way.
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Last edited by karbomusic; 05-26-2019 at 07:20 AM.
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Old 05-26-2019, 07:35 AM   #40
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I could have gone to about +1000dBFS and still been fine @32bit float. (Reapers internal default is 64 bit FYI).
And as it's floating point this also holds for -1000

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