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Gain Staging

Discussion in 'Recording' started by music293, Jun 4, 2009.

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  1. music293

    music293 Active Member

    I am currently trying to explain why proper gain staging is so important at all points through out a mix, and why you would want to leave about -10db of headroom on your final mixdown before mastering to a friend and I am apparently not doing a very good job.

    I was wondering if anyone could explain this in a better fashion, or if anyone can point me in the direction of some good reading material on this subject?

    Thanks in advance!

    -Matt
     
  2. Link555

    Link555 Well-Known Member

    So how are you explaining it?
     
  3. Codemonkey

    Codemonkey Well-Known Member

    Errr..... make them read this blog post by the guy from Massive Mastering.
    (Dead Link Removed)

    HEADROOM
    You cannot get enough of it
     
  4. music293

    music293 Active Member


    Well, simply put, I am explaining that if you record a track as hot as you can and begin adding your compression and e.q. to (generally) increase the db output all while constantly lowering the fader on a track is in the end sonically squishing your track.

    Also, that when you reach your master fader with your main mix, you want to be peaking (again, generally) at about -10db. This will leave you with enough headroom to send over to a mastering house, or apply your own in house master technique without distorting/clipping, or otherwise ruining your mix sonically.
     
  5. music293

    music293 Active Member


    This is good material, thank you.

    Though I'm not sure it fully explains the importance of proper gain staging? It focuses more on the actual input, which is great, but I am also trying to explain when you bus your signal over to another channel or use compression/eq.

    But thanks for the link!! :)
     
  6. Codemonkey

    Codemonkey Well-Known Member

    Input is a gain stage.

    Busing, and every plugin, is also a gain stage. ;)
     
  7. Link555

    Link555 Well-Known Member


    Ok a few things to expand on here is:
    The pre-amp- What is it function? It takes the lower voltage output of your mic and amplifies it essential to a line level. In gain staging it is important to put the main amplification as close to the orginal signal possible.

    Here is why:
    Say your noise in a given system is 10mV, and say your mics output is 20mV-100mV. When the mic transduces quiet sources at 20mV the 10mv noise will add in and be 1/3 of the total signal!

    Now if you amplify the input signal as soon as it enters the system, by say 40dB (100:1) the input becomes 2 vollts. Now 2 Volts with 10mV on noise on it is 0.5% noise. This is not a real world example but it gives you the idea. Gain up front improves your signal to noise ratio.

    Your Daw ADC input, after your mic pre, expects a line level signal. So as long as your average input signal is about -15dBfs your ok. Too hot and you may clip your ADC with transient peaks. To low and your noise floor gets closer. However in most ADC's these days the noise floor is very low. In the world of tape your have more noise and a higher noise floor to deal with.

    In your DAW each insert, send and bus your send your signal too can be clipped. Maintaining a bit of headroom in each stage is a requirement, again -15dbFS is a healthy signal.

    For mastering the ME need the Headroom to work in as well, the same all over again.
     
  8. music293

    music293 Active Member

    Of course! But that is my point.

    Sonically speaking, taking a low input level track (say -12db) and compressing the heck out of it to +3db and then lowering the post fader by -3db before busing it over to another channel is not the same as a high input level track (say +3db) and compressing/limiting it down to -6db and then raising the post fader +6db before busing it over to another channel.

    Maybe I'm way off base here, but this was my understanding?
     
  9. music293

    music293 Active Member


    Link555, thank you, this is good advice, although I'm not great with some of the technical terms, the concept still applies.
     
  10. TheJackAttack

    TheJackAttack Distinguished Member

    Hold on there cowboy. If you are tracking at +3dB then you are WAY TOO HOT. All your tracks should be peaking in the -15 to -6 dB maximum range. Period. Even if you were just throwing out numbers you should conceptually understand you don't track with peaks even at -1dB.

    There is an active thread right now over in the mastering forum that says straight up if the peaks are at least -25dB (peaks not RMS) then you have enough gain for recording.

    Even if we are speaking of a hypothetical live sound situation, you do not want any individual stick to get hotter than -10dB or so otherwise you will overload your sub mixes and main bus when everything sums out.
     
  11. Link555

    Link555 Well-Known Member

    Typically Sum register is 32bits. That means the sum register can sum up to 4294967295 (dec) before a carry over is required (distortion).

    QUOTE below is from:
    http://www.sizes.com/units/decibel.htm

    "If the level of the analog signal is greater than the level assigned to the biggest possible number, there is no way of recording its actual value. Every level greater than the one assigned to the largest possible number is usually simply recorded as the largest possible number. The signal is "clipped." The dBFS scale provides a way of indicating how close one is coming to this undesirable situation.
    In such a system, the maximum level before clipping of a sine wave is -3 dBFS."


    Check this out:
    http://www.tcelectronic.com/media/specifying_audio_nab(1).pdf
     
  12. music293

    music293 Active Member


    Jack,

    I totally understand where I should be peaking while tracking, I am just using some arbitrary numbers to show a broad range to easily illustrate my point. Just see my tagline! :)
     
  13. TheJackAttack

    TheJackAttack Distinguished Member

    I figured. There are (hopefully) newbies searching the archives for their answers and I didn't want them to get more confuse-ed than they might already be.

    :cool:
     
  14. music293

    music293 Active Member

    Jack! Great point! I guess I didn't really specify that my numbers were arbitrary, and if anyone who doesn't know any better is giving this thread a read then they might take it literally. I will keep that in mind when I post in the future.
     
  15. BobRogers

    BobRogers Well-Known Member

    My short explanation of gain structure is this. In any PA or recording setup you have several volume controls in sequence. You can obviously adjust them in lots of ways to get the same final output volume. A good gain structure gives the maximum range between the noise floor and clipping.
     
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