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a question about Gain and Level


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hi everyone ,m new here,m a student major in sound ,i find that in this bbs the atmosphere is so good and i really benefit a lot from reading all the topics here.now i meet some questions and i hope i can get the answer here because it troubles me for many days.

just as we all know,a mixer or a recorder has a gain knob(or trim or sensitive) and a level knob (or fader),the gain knob controls the extent of the pre AMP while the level knob controls the "post"AMP ,the question is if i input a singnal and let it reach a certain volumn,for example volumn “X”,i may have many ways.a typical situation "A"is that i use a low gain for example ,the position of the gain knob is on 9 o`clock while the level knob is on 3`o clock. the other situation "B"is that i use a hign gain where the knob is on 3 o`clock and the level knob is on 9 o`clock.both "A"and"B" have the same loudness "X" and both the 2 singnal is good(not be clipped),which sound is better?manifestly "B"has less headroom and dynamics than "A" .but i mean as far as "singnal to noise ratio" is concerned,which is better?

i think the question can be present as another example:is there any differences between the AMP circuit of GAIN and the AMP circuit of level?if i want to magnify a singnal to a certain level,what is the difference between only using the gain to plus 3 dB and only using the level knob to plus 3 dB

?

the questions above seems to be very simple and basic,but i just can`t figure it out .so m here to ask for some help sincerely.thank you very much~

:)

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i believe that the signal-to-noise ratio is usually highest when the fader is at zero

i agree with you ,i think that means the singnal pass through the "fader" `s AMP 1:1 without any additional noise from inferior AMP circuit,but what if i use the fader to lessen the singnal level?does the background noise caused by the inferior AMP(fader`s AMP circuit)lessen?
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Hi, and welcome...

this is fairly basic...

the gain controls the amount of gain added to the incoming signal, and gain typically adds some noise, so the ideal is to set up the input gain (trim) for optimum signal to noise ratio without adding too much noise, or clipping the amplifier so as to better utilize the entire dynamic range of the circuit.

the fader is more of an attenuator of this amplified signal into the mix, relative to other inputs, and into the mixers output; if the preamp adds noise, clips, or otherwise distorts the input signal, that will be included what goes into the mix, and determined by the fader.

whatever happens first is passed on to the next step...

there are lots of excellent books to read about this...

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The names "Gain" and "Fader" to specifically designate input or output levels might hold for a few pieces of gear, but it's by no means universal.

Likewise, using those terms to specific an active or passive stage isn't universal at all. And if you're using software, both input and output level controls are likely to be simple multiplication, with a factor that is <1 for loss and >1 for gain.

Other than that, it's as The Senator said: you have to find the best setting for each, based on both distance from the noise floor (s/n) and either distortion (analog) or desired headroom before absolute destruction (digital). And that also depends on the box feeding the device you're controlling, and the one your box is feeding.

This is covered in many books. You can read the section from one of mine for free on Amazon. Go to "Producing Great Sound for Film and Video" and in the "look inside" box, search "Gain Staging".

They give you a couple of pages, starting with this:

post-2900-0-51483200-1354129991_thumb.pn

The section talks about analog, but elsewhere in the book it explains how the concepts apply to digital.

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The names "Gain" and "Fader" to specifically designate input or output levels might hold for a few pieces of gear, but it's by no means universal.

Likewise, using those terms to specific an active or passive stage isn't universal at all. And if you're using software, both input and output level controls are likely to be simple multiplication, with a factor that is <1 for loss and >1 for gain.

Other than that, it's as The Senator said: you have to find the best setting for each, based on both distance from the noise floor (s/n) and either distortion (analog) or desired headroom before absolute destruction (digital). And that also depends on the box feeding the device you're controlling, and the one your box is feeding.

This is covered in many books. You can read the section from one of mine for free on Amazon. Go to "Producing Great Sound for Film and Video" and in the "look inside" box, search "Gain Staging".

They give you a couple of pages, starting with this:

post-2900-0-51483200-1354129991_thumb.pn

The section talks about analog, but elsewhere in the book it explains how the concepts apply to digital.

Great book Jay! I own a copy myself!

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a typical situation "A"is that i use a low gain for example ,the position of the gain knob is on 9 o`clock while the level knob is on 3`o clock. the other situation "B"is that i use a hign gain where the knob is on 3 o`clock and the level knob is on 9 o`clock.both "A"and"B" have the same loudness "X" and both the 2 singnal is good(not be clipped),which sound is better?manifestly "B"has less headroom and dynamics than "A" .but i mean as far as "singnal to noise ratio" is concerned,which is better?

It depends on the specific mixers being used, the nature of the input signals (mike level, line level, or consumer line level), along with the desired levels of the signals being mixed. Ideally, I try to use make-up gain with trims so that everything coming in to the mixer -- whether a wireless mic or a wired mic or even a playback signal -- has a relative "normal" level at 12:00, or whatever you want to call a neutral value. The trim values are all over the place, but I try to make sure the signal coming in will never overload or clip the preamp, nor will it be so low that I wind up amplifying noise.

Jay Rose's books should be on every mixer's shelf. The concept of Gain Staging applies to several other aspects of picture and sound; we used the same ideas for years in color correction, where the input signal, adjusted signal, and output signal all had to be optimized in terms of Red/Green/Blue levels. Film photography is the same: proper exposure during photography, then the lab timing will fall into place much easier since the levels are neither too high nor too low. The principles are exactly the same as gain staging in audio, since if the signal is distorted early on, no amount of adjusting can fix it later on.

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consider any time you go through an electronic component (resistor, capacitor, etc,) you also get all the electrical noise associated with that component. the later you add gain to your signal, the more noise from all the other components also gets gained up. The earlier you gain up, the more signal to noise your push through those components.

also consider most likely than not, you are never adding gain post pre-amp, instead you are only cutting gain.

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Ideally, I try to use make-up gain with trims so that everything coming in to the mixer -- whether a wireless mic or a wired mic or even a playback signal -- has a relative "normal" level at 12:00, or whatever you want to call a neutral value.

+1

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  • 3 months later...

THX,benefit a lot:)

consider any time you go through an electronic component (resistor, capacitor, etc,) you also get all the electrical noise associated with that component. the later you add gain to your signal, the more noise from all the other components also gets gained up. The earlier you gain up, the more signal to noise your push through those components.


also consider most likely than not, you are never adding gain post pre-amp, instead you are only cutting gain.

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Thanks a lot :)

Hi, and welcome...
this is fairly basic...
the gain controls the amount of gain added to the incoming signal, and gain typically adds some noise, so the ideal is to set up the input gain (trim) for optimum signal to noise ratio without adding too much noise, or clipping the amplifier so as to better utilize the entire dynamic range of the circuit.
the fader is more of an attenuator of this amplified signal into the mix, relative to other inputs, and into the mixers output; if the preamp adds noise, clips, or otherwise distorts the input signal, that will be included what goes into the mix, and determined by the fader.
whatever happens first is passed on to the next step...
there are lots of excellent books to read about this...

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