Recording Level Meters ???

[ef37a]

This thread is a common theme in forums., people do seem boggled by the concepts.

I am however always bemused by the 'strangeness' people express for a scale going negative of a 0 level? The VU meter found on tape machines has 0 and then negative dBs. Yes, there is a bit of scale above 0 but only 3dB (x 1.414) and it IS red! Yes again, I know the rocky/pop chaps used to run the meters well into the red but anyone trying to record a string quarter with distortion below 1% would view 0VU as an absolute maximum (knowing also that the impending transfer to vinyl will further mangle the fidelity!) When Dolby A arrived many 'classical' recording engineers took only about half of the noise reduction and used the reduced signal level to clean up the signal.

Maybe the clock has ticked so long now that we have a generation that have never seen an OR tape machine leave alone used one?

Dave.

[Sam Spoons]

I wonder if a pint of beer analogy might help, a full glass represents 0dBFG and as you drink it it goes into negative numbers until the empty glass is represented by - infdBFG

[James Perrett]

I think we need to be really careful not to make things even more confusing here. I think the confusion in the original post is down to having two different scales right next to each other and both calibrated in dB. These scales are actually totally unrelated to each other but, because they are next to each other and look similar, they're very confusing to a newcomer. I'm still not sure that DigitalMusicProduction has grasped the fact that they are not related so we need to be very clear which scale we are talking about (the meter scale or the fader scale) in replies to this post.

[muzines]

I think the confusion in the original post is down to having two different scales right next to each other and both calibrated in dB. These scales are actually totally unrelated to each other but, because they are next to each other and look similar, they're very confusing to a newcomer. I'm still not sure that DigitalMusicProduction has grasped the fact that they are not related so we need to be very clear which scale we are talking about (the meter scale or the fader scale) in replies to this post.

I did try to spell this out earlier, in case it was missed (or maybe my description wasn't sufficiently clear:

Edit: To be clear, the numbers on the *fader* indicate how much dB to increase or decrease the volume level of the audio signal. 0 means "don't change it", +3 means "increase it by 3dB" etc.

The numbers on the *meter* indicate, in dBFS, the *level* (volume) of the signal going through the audio channel.

As you increase or decrease the fader, the signal's volume level gets changed accordingly, and you see the signal get louder or quieter on the meters accordingly.

I see the OP has also posted some questions over on GS now, which no doubt will likely confuse him still further.

At this stage, I'm really not clear on which parts the OP is getting, and which remain stumbling blocks. The thing is, you don't *need* to understand the *engineering* at all to make some nice music these days. Just as you don't need to know how a combustion engine works to drive down to the shops to get some milk, you don't *need* to understand the finer points of dB scales and floating point maths - just make sure the volume stays a bit below the "0" point, record your music, and be done with it. Make it no more difficult than it needs to be, especially if you struggle with some of the technical stuff.

However, if you want to be a car mechanic, rather than just pootle around town in the car, you *do* need to get to grips with the fundamentals of the engineering, which requires a lot of investment of time and effort.

I'll never suggest that learning the fundamentals is a bad idea, but if it's not *absolutely necessary* to achieve your initial goals, then just do the creative stuff, heed to advice to not distort your tracks (and it's not like the OP is even recording audio here, this is a sample-based virtual instrument, there is no audio recording involved at all), and make your art.

If you're not sure at the end, run it past another set of ears who can spot if you've made any major problems (it's a virtual instrument, so *nothing* is not undo-able), and get it done.

By the time you've released your tenth album, you'll no doubt have a much better grasp of the fundamentals through practice too.

I'm not sure there's much more I can add here that's not just retreading the same ground, so...

[ConcertinaChap]

To add to what has been said above I understand dB from a maths angle. Using dB allows multiplication to be replaced with addition.

I've noticed 0dB can be a sticking point. 0dB means multiply by 1.

This is because dB are to do with powers of a number and any number to the power of 0 is 1. Kind of counterintuitive maybe, but mathematically correct :

x^0 = 1

Positive powers of a number make the number bigger :

2^2 = 4

and negative powers of a number make the number smaller :

2^-1 = 0.5

so positive dB mean the signal is getting bigger (has a higher amplitude) and negative dB mean the signal is getting smaller (has a lower amplitude).

You will also see -infdB which means -infinity dB and this corresponds to an amplitude of 0.

For me this works as a good explanation and a useful reminder that dB's are logarhythmic.

CC

[DigitalMusicProduction]

Thanks to everyone for your support on this topic.

[Gilly1]

The reason for levels going from 0 to negative values is because a fader is just another form of a volume knob, and volume knobs are attenuators. They can't increase a voltage level, but can decrease it. This in opposition to gain devices - amplifiers - that can increase a signal amplitude.

I think this is not correct. Cadets aren't just attenuated, they can both increase the signal voltage level (if adjusted upwards from 0db position) or decrease/attenuate the signal voltage level (if adjusted downwards from 0db position)

[Sam Spoons]

On most mixers the fader scale goes from -infinity to +10 dB (or something similar) with, as Merlin says, 0dB equalling 'no change in level'. That makes sense but historically the first faders were passive attenuators which can't increase gain, when faders with some gain became available they just adjusted the scale accordingly?

Welcome to the forum BTW

[Wonks]

It all depends on the circuit and application. Faders themselves, as Sam says, are attenuators, and if used purely an an in-line device can only maintain or reduce reduce the signal level.

But they can also say form part of an active boost circuit, where the signal is first boosted by say +10 dB before the fader and then passed to the fader (which will have markings up to +10dB on it). At the fader's 0dB point, it will be attenuating the signal by -10dB.

[ef37a]

It all depends on the circuit and application. Faders themselves, as Sam says, are attenuators, and if used purely an an in-line device can only maintain or reduce reduce the signal level.

But they can also say form part of an active boost circuit, where the signal is first boosted by say +10 dB before the fader and then passed to the fader (which will have markings up to +10dB on it). At the fader's 0dB point, it will be attenuating the signal by -10dB.

This^ is all true and I know many 'musical people' don't want to get into the electrical facts of sound but it can help. Douglas Self's book Small Signal Audio Design is virtually devoid of mathematics but gives an very good introduction to the world of audio electronics and the ever present challenge between noise at one extreme and distortion at the other.
He also debunks a great many audio myths which can trap and confuse the newb.

IMHO the OP would also benefit from purchasing a small mixer and playing with its faders and gain controls. Many charity and Cash Genny shops have small Behringers and Mackies for little money. A mixer is in any case a very handy box to have around.

Dave.

[Hugh Robjohns]

I think this issue was put to bed 18 months ago... probably no need to rake through it all again.

[ef37a]

I think this issue was put to bed 18 months ago... probably no need to rake through it all again.

Wonks did not think so?

Dave.

[Hugh Robjohns]

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