gain staging question

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davecg321

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Hi

I have set up my preamp to my desired settings and am running this into my interface (making sure not to clip, no red lights!) in cubase. My audio in cubase is then peaking at around -5. However, I read that the ideal place to be peaking at is somewhere around -10. My question is, can I leave the fader at -0 (default position) and then drag the fader down after recording to achieve somewhere around -10 or thereabouts, or, do I bring the fader down (in cubase) before recording to achieve -10 at peaks?

any help would be greatly appreciated


tah

dave
 
The place to bring it down (if you need to) would be on your pre amp and/or your interface. Once the signal is into Cubase you're just playing with zeroes and ones, not the true level.

There's no one way to do gain staging, particularly when you can't measure absolute level every step of the way. The best you can do is make sure you level are all in a similar "good" range throughout the chain. The main thing to avoid is having one fader or pot up high and the next one down low to compensate (or vice versa of course). If everything is set to something like the same level--and you end up with the levels you want--then you're probably okay.

As for what level to aim for, if your PEAKS are at -5dB(FS), you never exceed that no matter how loud you go, and there's no sign of analogue clipping in your pre amp/interface part of the chain, then I wouldn't worry too much.

There are two or three reasons to keep your level relatively low. First, you need enough headroom--at every stage in your system, not just once it gets into Cubase--to make sure you never get to clipping. If your peaks truly never exceed -5dB(FS) then you've achieved this, though maybe with not quite enough leeway when things get really hot.

Second, when you add tracks together in a mix the levels are cumulative. If everything is up highish, then you just have to turn things down to avoid clipping when the tracks are mixed together. (I'll ignore Floating Point systems here for brevity.) It's not a big deal to turn things down a bit though--so long as you're not having problems, then don't worry.

Third, and a bit more in the realms of "maybe", if you add effects with a few plug ins that try to act like analogue outboard gear or if you actually use analogue outboard gear, then it's possible for high levels in the digital domain to cause clipping...but, in my experience, this is rare. Most plug ins and D to A converters are set to pass levels of 0dB(FS) because that's how most mixes end up in these days of loudness wars.

(As a brief background, 0dB(VU) is generally regarded as being equivalent to -18dB(FS). In the analogue world you'd tend to work with your signal averaging around the 0dB(VU) mark and peaks going to, say, +8 or even +12 dB(VU) depending on the headroom in your recording chain. A bit of maths will tell you that +8dB(VU) is roughly equivalent to -10dB(FS) in the digital domain--but this is a guideline not a hard and fast rule.)

So, after several paragraphs of waffle, if you want to knock 5dB off your levels, do it at the pre amp/interface stage. However, if you're happy with your recordings now, I wouldn't worry about it.
 
I would say that, depending on your pre-amp, you should change the gain at the interface. I say this because some pres change tone, response, etc depending on your settings. If you have a "straight wire and some gain" pre, then yeah, you can cut there, but if you have a pre that has some character to it, try changing at the interface.

(disclaimer: i'm no pro. If i say something wrong, I'm sorry.)
 
The proper recording level is 0dbVU. The problem with that is the meters in cubase read dbfs, which is completely different.

Basically, you want to feed the converters a line level signal and only worry about the peak level if it gets too close to clipping. Some instruments will have a low peak level, things like violins dont have a large transient so the peak level and the average level are nearly the same. things like drums have a very sharp attack transient and very little sustain, so they have a very low average level.

Peak meters, the ones in cubase and all digital equipment are only good for finding peak levels, which is of limited use in proper gain staging. If there are meters on your preamps, shoot for 0dbVU on the preamp meters. Set the interface at unity gain, if there is an adjustment on the line input. ( you should be using a line input, not a mic input). Check to make sure the peak levels are only getting to about -6 or so (mainly room for surprises) and only adjust the recording level from your preamp.

The reason you can't adjust the recording level on the faders in cubase is because, once the faders in cubase see the audio, it has already been recorded. It's too late to set the recording level.

The point of proper recording levels is to keep the signal in the sweet spot of all the analog equipment and the converters. Once the signal is digital, the levels really dont matter much. If you distort the levels during recording, it cannot be undone in the computer.
 
While I mainly agree with Farview, let me quibble over a few small points.

First, 0dB(VU) is a reference level, not a recording level to aim for. Analogue gear in the chain always has a fair margin of headroom above that, typically between 18 and 22 dB before the onset of clipping. The norm while recording analogue was to let peaks eat into this margin above the reference level. How much into the headroom? That depended on the gear and there was no formal standard. On some pieces of gear, clipping started earlier, on others signal to noise was an issue so we'd push levels as much as possible.

Second, virtually every meter you see these days (other than ones talked about in the analogue forum) is a PPM (Peak Programme Meter) rather than a traditional VU...so levels monitored on the meters should take this into account and be used for peaks rather than be considered the "average" level. Alas, other than being a form of peak meter, there are varying standards for the ballistics and peak hold time. Unlike the days when I used BBC or EBU standard PPM meters with a very specific spec, you just have to get used to your metering system. Just as an example, the BBC spec for audio transmission is to have speech at between +4 and +8 on their PPMs with music going to between +8 and +12. Then came digital satellites where we had to lower levels because the encoders started clipping at +12 so we set an arbitrary limit of +8 (and used a limiter at this level).

I go into all this detail because what levels to shoot for on meters depend on what type of meters you have. If they're PPM (and if they're LEDs rather than needles this is almost certainly the case) then 0dB on the meter is way too low.

Finally, a slight disagreement on the link between an external pre amp and an interface. For proper gain staging, don't set the interface to unity and adjust just the pre amp. Your goal should be to have the pre amp and interface at roughly the same setting so you're not artificially adding or removing gain along the way.

Just quibbles I know, but it's a pet subject for me!
 
thanks guys... this has clearned up some issues, i think ;) my levels are now roughly peaking at 0dbvu on my preamp, with peaking somewhere around the -6db mark on my interface (with the same in cubase)

I know many people do this gain staging thing differently from person to person. I just wanted to check I wasn't doing something totally off mark


cheers
 
Not totally off mark at all but...

...with the different scales you're using your interface to crank the pre amp signal up by about 12 dB. I'd probably nudge the pre amp up just a few dB and the interface down by a similar amount.

Why? Right now you probably have 18dB headroom on the pre amp but only 6 dB headroom on the interface. This means the pre amp would be capable of driving the interface into clipping if things ever got loud accidentally. A slight increase on the pre combined with a decrease on the interface just evens things out a bit and maximises your headroom through the full chain.

Or, if you want to aim for that -10dB peak number, just back off the interface slightly.
 
Ooo! The trials and tribulations of decibabbles!

I note that the OP's pre amp seems to be the Marshall JMP-1 guitar pre amp so he will probably want to run that pretty hot?

Do we know what the AI is? Some of them are not noted for high line in headroom.

Dave.
 
I aim for -18dBFS as the average level when recording, then get peaks around -10dBFS, since doing it my recording have sound better
 
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