mixer: gain vs. level?

Posted: Wed Mar 15, 2006 12:09 pm

I'm just curious, can someone explain your gain settings on a mixer's preamp section vs. the "level" (volume) setting? It the level passive attenuation while the gain is true amplification?

What confuses me is the Level goes from -infinity (no sound) to 0 in the middle which I thought would be full level... but it also goes upto 10 leading me to believe that's some sort of boost? That's on even the line levels though as well. Gain is only present on mix preamps.

Posted: Wed Mar 15, 2006 1:27 pm

gain is an engineering and mathematical term that sometimes gets used wrongly
and
level is also something that can be misleading

You may hear people talk about gain structure of the mixing desk

lets simplify

Mostly the mixing desk is mixing audio signal and and can add an EQ effect to the sound and then can output various options of this mix

Basically this is all at LINE level ... Line level is loud
A microphone's output is very low .... Mic-level is quiet

we use a Mic level to LINE level amplifier ...
Mic to Line amp ... a Pre-Amp
these may have a GAIN controls ... and some are fixed gain amps
The marking can be different depending on the point of view of the makers
-60dB might take a quiet signal of -60dBu and bring it up to 0dBu
and 0dB is no added gain
some other units might say 60dB and this means they ADD 60dB and again 0dB adds 0dB
0dB may handle a line level but with very little headroom

Faders are generally a passive resistive divider between buffer stages in the mixer
the can also be labelled in various ways
0 down to -60 and more
10 down to 0 or similar arbitrary scale
+10 down to 0 and then down to -60
(the 0 tends to mean a unity level transfer through the buffer stage including the fader)

As always you should check and learn how the mixer is working before diving in to do something complicated with a mix

Posted: Thu Mar 16, 2006 12:07 am

Kev is another wonderful person with a wealth of information and I think his explanation was excellent! What he did not clarify for you were the markings on your linear slide faders. That is the way most studio console, logarithmic audio taper faders are marked and calibrated. Those markings are decibels. The reason the " 0 " is one third from the top, is the fact that most consoles refer to that position as the "unity gain" position. An additional 10 or more decibels are available beyond the unity gain position. Conversely, when you fade things down, your fadeout point will be at maximum or " Infinity" attenuation, i.e. nothing.

Sometimes you will find your master output or subgroup faders will not have the same calibration. Those may actually indicate " 0 " at the very top. Indicating that those master outputs or subgroups should be set there, for proper output level. From there, you can also do a better smooth fadeout since you'll have a greater excursion.

Few people realize, when operating an audio console, for a PA system or recording environment, all your faders should be set to the " 0 " position and then the " gain trim " should be adjusted for proper output and mix levels. So often I see people running an audio board with their faders much too low and their gain trim, much too high. This may yield slightly lower noise from an audio console but it will blow your head room all to hell! (and it usually indicates they generally don't know what they are doing) I actually prefer to run my gain trim slightly lower on my microphone preamplifiers and then I will push my faders, so that they are slightly higher above the unity gain or 0 position. The reason I do this (mostly on cheaper boards) is that the headroom is improved this way by a few more decibels, which can be quite significant sounding. I'm not working the microphone preamplifier as hard that way.

"Headroom" is the uppermost point before clipping and distortion occur. I like lots of headroom (I don't know a professional engineer who doesn't)! That's why audio consoles like API, Neve, SSL and other professional consoles are so popular. They have lots and lots of headroom! When you have lots of headroom, your transients have much less opportunity to clip or distort. That's why good consoles generally sound better than cheap consoles. Most inexpensive consoles just never have enough headroom for good transient response, unless you cheat like I do on them.

Headroom cheater
Ms. Remy Ann David

Posted: Thu Mar 16, 2006 8:32 am

RemyRAD wrote:

Few people realize, when operating an audio console, for a PA system or recording environment, all your faders should be set to the " 0 " position and then the " gain trim " should be adjusted for proper output and mix levels.

I do basically the same thing, but I set my faders to 0 and then adjust the gain so that the signal is showing 0 on the meters. That doesn't necessarily mean that the fader will be at 0 while mixing.

Posted: Thu Mar 16, 2006 11:46 am

RemyRAD wrote:

What he did not clarify for you were the markings on your linear slide faders.
...Most inexpensive consoles just never have enough headroom for good transient response, unless you cheat like I do on them.

yeah
apart from the small print comment
I didn't want to get into that or even into the linear vers log scale

desks and software is built and configured differently and you have to get to know your gear

Gain Structure and Headroom may be boring terms used by audio geeks
but
once you understand the implications of what they mean ... so many things begin to fall into place

the same goes for dB levels and termination and the inter-connectivity of equipment
particularly in the analog domain

even digital connections and transfers can have these issues
look at how many Peak Meter standards there are out there

why do I side track ?

because it all rolls back to Headroom and then to Gain Structure

Posted: Mon Mar 20, 2006 9:26 am

so, levels should be kept at 0 and the preamp gain should be used to set levels. then, the levels are for attenuation, to gain more headroom?

why does the level goto +10, is that an arbitrary scale?

if that's wrong or if you want to get more technical feel free, you wont confuse me. thanks guys...

Posted: Mon Mar 20, 2006 11:32 am

jcnoernberg wrote:

so, levels should be kept at 0 ...

levels should be near the nominal level for the desk
in this case it could well be 0dB

yes the mic gain is used to bring the levels up to the nominal

jcnoernberg wrote:

the levels are for attenuation, to gain more headroom? ...

the faders are used to mix the multiple inputs to a desired level
... and this may have nothing to do with technical requirements

this could lead to more headroom but again is not the primary reason for faders

often people do lower the faders of a desk as an acknowledgment that their desk does not have the headroom it should

headroom is something that is firstly in the hands of the designer when it comes to analog gear
but an operator can use the gear to best optimise the equipment for the given task

Digital gear has the 0dBFS at which you can't go louder ... period
all gear works under this
I like to work with digital as this 0dBFS is a very clear boundary.

Boundaries are not so easy to see with the analog gear.
Always check your specs and compare apples with apples.

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