Difference between GAIN and LEVEL

L

LiveMusic

New member
I know enough about recording to be dangerous. I bought an SM57. I am going through a Behringer UB1002 mixer (I know, I know) and it has a Gain knob on Channels 1 and 2. As well as Level knob.

I feel that I need to crank up the Gain to get a hotter signal when micing an acoustic guitar? Then again, I don't understand the difference between Gain and Level. I am wanting to get it as hot as I can get it, I suppose, without feedback. Thanks for explaining this basic question.
 
LiveMusic said:
I know enough about recording to be dangerous. I bought an SM57. I am going through a Behringer UB1002 mixer (I know, I know) and it has a Gain knob on Channels 1 and 2. As well as Level knob.

I feel that I need to crank up the Gain to get a hotter signal when micing an acoustic guitar? Then again, I don't understand the difference between Gain and Level. I am wanting to get it as hot as I can get it, I suppose, without feedback. Thanks for explaining this basic question.
Click to expand...
Gain and level are used a bit differently in a live PA situation and recording.
Gain is used for matching the sources (mic) output level to the input of the board. This way the board is operating at optimum level (everything beyond the input stage). Keep in mind the board is desingned to accept a huge range of sources. It has to be able to "adapt" to those situations, and you are in control of that.

Level is for "mixing" the audio, you don't use "gain" to do that. Gain is kind of set it and forget it as long as the source hasn't changed (got way louder, etc). In a live situation, it's just unrealistic to expect everything to stay controlled as it was during sound check. If you ever see the input clipping, you know you need to back off the gain. And if you are pushing the Fader past unity(0), you probably need more gain. Hopefully you'll have all that set properly before a show. Otherwise you'll have to correct it real-time and you might cause feedback or cause a mic to get quiet while you tweak it.

Live, your goal is to get as lout as possible before feedback, then mix everything for the best live sound.
Recording the goal is to have optimum recording level. So, mixing is out of the question. The Level slider should be set at Unity, and gain will determine the recording level.
Mixdown is similar to Live, set the gain once (you have the advantage of knowing all the source levels since they're pre-recorded). Then mix the audio how it sounds best using the Level sliders. But generally you don't want to go over unity unless you're sure your mixer will still sound good up there. then you use the Master fader to determine the overall output level to the mixdown destination.

OkOK.....
That was probably kind of confusing. So I'll break it down as how I usually set gain.

Live:
--Turn Fader "level" all the way down.
--Play source as loud as possible (sound check). (also a good FOH eng will mute the channel or subgroup during this time, nobody wants to hear 20 rack tom hits as you set the gain.)
--Turn up "gain" until you see "ol" or "clip" light come on, and then back off a --little bit from there.
--Now use the "fader" to turn it up to taste.

Tracking:
--Turn "Fader" to "Unity" (or 0). (make sure "gain" is down all the way first)
--Play the source as loud as will be recorded.
--While that's playing, turn up "gain" until your recorder (DAW, tape) has optimum level.

Mixdown/Summing:
--same as Live above
 
That was good, Tarnation.

Another example of the difference between "gain" and "level" is how my TASCAM 2488 works. If I'm recording onto a track, the "Gain" (input) is how much signal is coming into the track, thus deciding the recording level. The "level" (volume) is for monitoring. I can play with the level all I want and, while it will change the volume of playback, it won't affect the volume of the recording. Only the gain will change the volume of the recorded signal.

It can get confusing because the words are almost interchangeable. e.g: "Trun down the level of the gain". :D:D:D
 
+1 to what Tarnation described.

Just to try and put a basic concept on the top of that description...

On a mixer, the "Gain" - which can also be called "Input" or "Trim", depending upon the mixer brand - sets the signal level at the input, or start, of the mixer channel strip, and the "Level" (or "channel fader") sets the signal level coming out of the "end" of the channel strip.*

Looking it it from a signal flow perspective like that not only helps understand the difference, but reflects a very important concept called "gain staging", of which now is as good a time as any for you to look into, LM. Gain staging in short means making sure you have the proper or ideal signal level at each link or point in your signal chain all the way from microphone to recorder. The input trim "Gain" and channel fader "Level" at the beginning and end of each of your mixer channel strips are important waypoints in that overall signal chain.

*That's a simplified description that bypasses some more sophisticated signal routing options (pre fader/post fader routes, inserts, etc.) Don't worry about all that for this discussion.

G.
 
tarnationsauce2 said:
Live:
--Turn Fader "level" all the way down.
--Play source as loud as possible (sound check). (also a good FOH eng will mute the channel or subgroup during this time, nobody wants to hear 20 rack tom hits as you set the gain.)
--Turn up "gain" until you see "ol" or "clip" light come on, and then back off a --little bit from there.
--Now use the "fader" to turn it up to taste.

Tracking:
--Turn "Fader" to "Unity" (or 0). (make sure "gain" is down all the way first)
--Play the source as loud as will be recorded.
--While that's playing, turn up "gain" until your recorder (DAW, tape) has optimum level.

Mixdown/Summing:
--same as Live above
Click to expand...
When I set the gain structure I do it a little different. I put the channel and main faders at unity with no gain and then turn up the trim (gain) on each channel until it clips and then back off a hair. Then I use the faders to mix to taste.

What's the advantage to doing it the way you described and could you explain why you would do it differently Live than for tracking. Also, what do you do when you track a live performance?
 
I look at it as the gain being the absolute volume of the signal, while the level controls the relative volume, in relation to the other channels.
 
I try to think in the simplest terms possible. I may be way off on this but I think of gain as the preamp volume and level as the output volume, faders are to balance the total output. I know this isn't a very accurate description, just my way of looking at it.
 
So if I'm tracking at home, one track at a time, can I fuck the "quality" up by not gain staging?

So far I've just turned the gain and level up as much as I (thought) I need to get the signal I want. Can I get better quality by caring about what (gain or level) I turn up/down on the mixer?

Also, is there a way to determine in Cubase what the average level of the signal is, instead of just getting the peaks?
 
LiveMusic said:
Then again, I don't understand the difference between Gain and Level. I am wanting to get it as hot as I can get it, I suppose, without feedback. Thanks for explaining this basic question.
Click to expand...

LEVEL: The strength of a signal measured by some standard method (peak or averaging) and reported relative to some standard reference level (say, 0 dBu = 0.775 V RMS for a voltage signal or 0 dBFS for a digital file)

GAIN: For a signal processing stage, the ratio of the output level to the input level. Usually measured in decibels or dB. Unity gain means that input and output levels are the same (gain = 0 dB). In dB, a positive gain value means amplification, negative gain means attenuation.

Preamps (separate units or the preamp gain stage in console inputs) bring low level mike signals up to standard line levels. Typical gain settings are +40 dB to +70 dB, depending on the output level of the mike and the loudness of what is being recorded. More gain is needed on dynamic and ribbon mikes, less gain on phantom powered condenser mikes with built in preamp circuits. More gain is needed on acoustic guitar (maybe all you've got if you're using a dynamic) than on a close miked guitar amp turned up to 10 (might require almost no gain at all).

Faders are usually used to attenuate line level signals when mixing. If a track is in the mix, the fader will be up somewhere around unity gain, depending upon the exact loudness of the track itself and how it fits into the mix.

Cheers,

Otto
 
Lomas said:
So far I've just turned the gain and level up as much as I (thought) I need to get the signal I want. Can I get better quality by caring about what (gain or level) I turn up/down on the mixer?
Click to expand...
Gain staging is *very* important to getting good quality tracking.

The analog gear (preamps, mixers, tape recorders, compressors, EQ, etc.) you are running your signal through is all *designed* to operate at a nominal signal level, meaning that it will work the way their manufacturers intended it to when you are not running the signal too hot or too cold. For most of these analog devices, that means a signal hovering around line level voltage, and for most of these analog devices with VU meters, the meters are calibrated so that line level voltage = 0VU on the meters. (Some tape recorders calibrate their VU meters so that 0VU equals tape saturation on a reference tape formula, check your manuals there.)

That said, sometimes we may want to overdirve something - push it past it's optimal design level - in order to get a certain type of distortion we think is pleasurable. That clunky old tube compressor sounds really boss if it's preamp is overdriven, or if you over saturate that tape a bit someting similar may happen.

But you'll want to keep that overdriving in the box and not send it down the line; you want to set the proper levels at each *stage* in the process. Hence the name "gain STAGING" :). Just because you're overdriving your mic pre to get a crunchy 50s Little Richard sound doesn't mean you want to send the signal too hot to the next device in the chain. Once you have that distortion you want, then use either the output gain on that box or the input gain on the next box in line, or a combo of the two to get the signal back to normal levels for the rest of the signal chain.

This is important at the mixer as well. The input gain sets the level going into the preamp at the head of the mixer channel strip. You want to set that both to get the preamp operating at it's designed efficient level and to get that nominal signal level sent down the rest of the channel strip as well. The level fader sets the level coming out of the end of the channel strip and into whatever buss(s) you have that strip assigned to.

Here again, 0VU is typically the meter level to shoot for to reflect that. But since that meter (on most mixers) is reading what coming out the bottom of the strip - i.e. the post-fader signal - it will be reading the combination of both the input gain and the fader level settings. *It is for this reason* that it is common procedure to set the fader to "unity" - i.e. zero boost/zero cut, typically marked at about 2/3rds to 3/4ers of the way up the fader control - and then set the input gain to give a nominal 0VU reading on the meter. This has the triple effect of a)setting the preamp to nominal operating level, 2)sending nominal operating level voltage through the rest of the channel strip, and iii) calibrating the fader control at the bottom of the strip so that unity gain is calibrated to 0VU on the meter, making a handy and easy reference for riding the faders without having to woory about the actual metering too much.

HTH,

G.
 
Stellar thread. Thanks everyone. The one lingering question I have is the difference between why the gain/trim opens up the microphone more than the channel fader?

For example, in podcasting we often deal with less than perfect recording environments. One way to compensate for reverb and background noise is to lower the gain and increase the channel fader to achieve the proper level.

Why does the channel fader not open up the mic. as much as the gain knob? What's going on with the way these two work?

And what's the danger of setting up a mixer this way if any? If the channel fader is up most of the way and the gain is well below where it would be in a proper setup but you are getting good levels is there a problem with that setup?

Again, the main question is how are gain and the channel fader different in terms of how they affect the microphone's sensitivity?
 
It's an 8-year old thread....but anyway...the gain at the preamp for the mic...the level is just the output post-preamp.

If you set the preamp gain low, the output level is simply adjusting what you did with the preamp.

Think of the gain as what controls the mic output...and the fader is what you use to set the level for the next stage of the signal path, and not what controls the mic level.

One is input level and the other is output level.
 
Ray Ortega said:
..For example, in podcasting we often deal with less than perfect recording environments. One way to compensate for reverb and background noise is to lower the gain and increase the channel fader to achieve the proper level.

Why does the channel fader not open up the mic. as much as the gain knob? What's going on with the way these two work?

Again, the main question is how are gain and the channel fader different in terms of how they affect the microphone's sensitivity?
Click to expand...
Unless there were some other variable missing in a scenario like that, it simply isn't true. I.e. the dynamic contrast (ratio) between the desired content, 'background or 'softer or unwanted content at the mic, isn't changed by where the level is increased.

And what's the danger of setting up a mixer this way if any? If the channel fader is up most of the way and the gain is well below where it would be in a proper setup but you are getting good levels is there a problem with that setup?
Click to expand...
The main factor (and general goal/rule of thumb') is to get the input gains reasonably within nominal operating range as early in the chain as possible- to establish optimal signal to noise quality for the whole system.

to add, then the downside (input gain below nominal, made up in level downstream) presumably would be some amount of degradation in system noise, but still no dif in the rendering on the acoustical situation.
 
Think of it as a manual gear change car. You can change speed by changing the speed of the engine, but you also have a gearbox. So you can do 40mph in maybe gears 2,3,4 and 5. Gain staging is very similar to choosing the right gear for the conditions. From in to out your equipment has many separate sections that do various things, so gain staging means each one works at it's optimum and although sound comes out the end, like a car doing 40 in 2nd or 5th, it's not good for quality.
 
Back to the original question, "Gain" is the amount of change you're applying to a signal. "Level" is an absolute measurement of your signal. This level can be expressed with various starting points which can be expressed with a notation like dBu, dBV, dB(FS) and so on. The notation is important. In most cases there's an arbitrary zero level, meaning that level figures can be expressed as plus or minus numbers. For example, mic outputs are often in the -50 to -30dBu range. After your mic preamp and faders, you'll be int the + range. The exception to all this is dB(FS) where zero is an absolute maximum and anything above that clips.

As an example, your mic might be putting out a "level" of -40dBu on peaks. You put it through your mic pre amp and apply 50dB of "Gain" (i.e. +50dB gain). This gives you a new "Level" of +10dBu.

As you can see for other posts above, there are lots of ways to adjust the gain to set your levels. My personal way of working with a mixer is to set the fader to zero and then adjust the channel gain so the meter is mid-green. I don't run any individual channel much higher because the act of mixing 16 or 24 or 48 channels together is cumulative.

Or, if working with an interface in the studio (i.e. no fader) I just adjust things so absolute peaks are around -6dB(FS) with the vast majority of a recording much lower...say between -18 and -12. Some will say this is a bit too hot but it also depends on what you're recording, i.e. the dynamic range.
 
Thanks Bobbsy:
I think I get the lingo now.
I start with a level & add gain to achieve a new level.
Gain is the amount added as in 7 + 5 = 12.
5 is the gain that takes me from 7 to 12.
 
Exactly that.

Just to confuse more, you can have negative gain (technically known as attenuation) which reduces level. However, they're two sides of the same coin.
 
rayc said:
Thanks Bobbsy:
I think I get the lingo now.
I start with a level & add gain to achieve a new level.
Gain is the amount added as in 7 + 5 = 12.
5 is the gain that takes me from 7 to 12.
Click to expand...
In db, yes. A 7db signal plus 5db gain will come out at 12db.

I should probably leave it there, but at the actual circuit level we're not talking about db, we're dealing with volts, and in that case gain is actually a ratio of the output to the input. It is multiplication or division, not addition or subtraction. The decibels thing actually represents that ratio after it's been logarithmatized.
 
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