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mixer: gain vs. level?

Discussion in 'Recording' started by jcnoernberg, Mar 15, 2006.

  1. jcnoernberg

    jcnoernberg Guest

    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.
     
  2. Kev

    Kev Well-Known Member

    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
     
  3. RemyRAD

    RemyRAD Guest

    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
     
  4. 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.
     
  5. Kev

    Kev Well-Known Member

    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
     
  6. jcnoernberg

    jcnoernberg Guest

    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...
     
  7. Kev

    Kev Well-Known Member

    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

    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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