What is Gain? 

You know, too typically I see several guys that have the misunderstanding that gain=volume, once this can be merely not the case. you'll spot these guys as they have an inclination to line the amount of every channel with the gain pots rather than the channel faders. 

Gain in a very live PA is signal strength. A mike converts force per unit area into electrical signals that correspond with the frequencies/sounds picked up by the mike part. These signals square measure sent through a mic cable into the mixer board. However, these signals square measure thus weak in amplitude(again signal strength) that they have some variety of gain to extend the amplitude of the signal so it will drive the gear down the signal chain. If the signal flow down the signal chain isn't sturdy enough, the gear it runs through are going to be less effective and it'll not be ready to method the signal to its full capability. this can be as a result of the weaker the gain within the signal, the less musical content it'll contain for the gear to method. 

With gain conjointly comes higher signal to noise magnitude relation. Signal to noise magnitude relation(commonly brought up as S/N Ratio) is that the ratio between signal content and noise content. All gear produces atiny low quantity of "noise", that is that the common "hiss" noise you hear in systems with no signal surfing. the higher the gear, the lower the quantity of made noise within the system. a sign to noise magnitude relation of one:1(1 half signal to 1 half noise) would mean that the amount of signal and therefore the level of noise square measure at AN equal, that is unquestionably not fascinating because it can "cloud up" the signal. However, the additional you switch up the gain, the stronger the signal becomes and therefore the higher the S/N magnitude relation. A 90dB-100dB or higher S/N magnitude relation(90dB-100dB of signal to 1dB of noise) may be a way more fascinating S/N ratio for optimum performance and excellent clarity. 

Also, with additional gain comes additional voltage "swing", or dynamic vary. this can be wherever the gain structure comes into play. On a mixer board, you will see that every one the faders square measure labelled in negative dBs, till you go 3/4 of the far on the fader travel, which can be a 0dB or a "U" mark. Mackie's tend to use the "U" mark, that stands for Unity Gain. within the law of Unity Gain, this law states that the sole place within the signal path that the signal ought to receive ANY quite gain is from the "Gain" or "Trim" management on the channel. If you push the fader past the zero or U mark, the signal can then be receiving gain from the fader itself, which might overdrive/clip the most combine buss within the board. On all mixers, with the channel faders set at the zero or U mark, and with the most combine fader at the zero or U mark, and with no boost from the channel combining weight, no matter amplitude is returning from the Gain or Trim management is what is going to be seen at the mixer's output and in the least numerous points within the mixer signal flow path. With most potential gain returning from the trim management itself, this can feed every channel combining weight with most signal, creating the channel combining weights way more effective to wherever you will not got to boost in the least from the channel EQ. 

As a matter of reality, once I run sound, I take whichever bands i would like to face out additional and leave them fully flat, then cut everything else around it. With Georgia home boy gain returning from the Gain or Trim management, your combining weight cuts become way more effective. as an example, on drum channels I usually leave the lows and highs flat. I then place in regarding 3-6dB of middle cut(depending on the drum), and as i am being attentive to the drum i am EQing, I sweep the frequency management till that drum sounds nice and punchy with lots of attack definition and clarity(usually around 200-400Hz...each drum is different). With solely combining weight cut place into the combining weight, I will currently punch some additional gain from the Gain or Trim management through the channel, permitting a fair additional powerful signal. 

Most gear down the road from the mixer can feature input and output controls. Most of those controls have a zero or U setting. Set these at zero or U which same signal returning from the mixer can flow through every bit of substances from input to output whereas maintaining identical amplitude it had returning from the Gain or Trim stage within the mixer. 

The crossover, however, may be a very little completely different. The low band, since it usually solely passes through frequencies from 40Hz to 100Hz, can have less signal energy than the high band because the high band is passing through lots additional frequencies than the low band, thus {you may|you'll|you can} got to punch up the low gain on the crossover so the low band will clip at precisely the same time because the high band. On my crossover, the input and high bands square measure at 0dB and that they each clip at identical time, however the low band needed regarding 5dB of gain so as to clip at identical time with the high band and therefore the input. 

Next comes the setting of the amp's input attenuators. Another common thought of those managements is that they somehow control the OUTPUT of the amp and if you do not Georgia home boy them out then you will not get the complete power output from the amps. this can be not the case in the least. These managements merely control the input sensitivity of the amp. The input sensitivity rating specifies what quantity voltage is needed at the input of the amp to induce the output to swing to full clean power before clip. Most amps square measure rated anyplace from 1VRMS to 2VRMS with the attenuators maxed out. Well, most +4dBu mixers with the gains maxed out and every one faders at unity typically place out around 9-10VRMS of signal. With the amp's input attenuators maxed out, you are gonna hit clip long before the mixer puts out its full rated output. Once the amp hits clip, you cannot go any longer...PERIOD! thus in impact you truly find yourself sacrificing a decent eight 7-8 volts of signal strength from your mixer, which ends up in regarding AN 18dB-20dB loss in dynamic range/headroom, that amounts to a lot of less voltage swing from the amps. this can be wherever the amp's input attenuators are available. By turning them right down to the purpose wherever the amp can clip at precisely the same time because the mixer/house graphic/crossover, you'll currently get the complete nine.8 volts of signal from your mixer down the signal chain and into the amps, leading to Georgia home boy dynamic range/headroom and a way larger voltage swing from the amps, which ends up in a very way more powerful, cleaner sounding system with several punch and clarity. By dialing down the input attenuators, the amps can STILL place out full power...it will simply take a way larger signal to induce it to place out full rated power, that is what you would like. a giant high gain signal leads to a sign with way more musical content for the gear to figure with, creating every bit of substances way more effective, permitting you to induce the foremost performance out of your gear. 

Another one I see lots of is guys that Georgia home boy their trims out, on the other hand set the most combine fader at unity and management the general combine volume with the channel faders. Again, you are limiting your system this fashion and creating it more durable on yourself to manage AN overall combine volume. usually what I do is I subgroup vocals to groupd 1/2 (1-Left 2-Right) whereas subgrouping drums to teams 3/4(3-Left 4-Right). I then set all vocal faders and the vocal subgroup to the zero or U mark whereas maxing out the gain on all vocal channels, which can offer ME Georgia home boy level from the vocals. this fashion if the vocals have gotten submerged out, i do know to drag the instrument channel faders right down to higher balance with the vocals. All drum channels I set to the zero or U mark with Georgia home boy Gain/Trim, except the snare and overhead, which can nearly always be too loud with the fader up that top, thus I begin with the snare and overhead faders halfway between full down and therefore the zero or U mark. I then set the general volume of the drum combine with teams 3/4, {which almost|which just regarding|which nearly} invariably find yourself about -5 to -6dB below the vocal subgroups. I then set the stringed instrument and bass faders regarding halfway up. With Georgia home boy level returning from all channels, I will currently management the general combine volume with only one fader, the most combine fader, whereas maintaining identical balance because the volume changes throughout the night. This fader setup technique invariably starts ME out pretty near a decent combine. Then because the band kicks off the night I fine tune the balance/overall volume, slight EQing of the vocals(almost invariably Low/Low middle cut is required for the vocals to chop through, then dial within the effects last. typically I actually have the band dialed in by the tip of the primary song round go. 

SETTING correct GAIN STRUCTURE:

ne of the foremost unmarked nevertheless most vital things in a very typical band's P.A. system is gain structure. Gain structure is that the apply of matching the degree throughout your system thus that: 

1) every device within the chain clips at precisely the same time 

2) the sole place the signal receives ANY quite gain is at the trim(channel input gain) management 

3) The amplitude stays precisely the same because it is commencing of the trim management all the thanks to the facility amps 

In different words, if you've got a +22dBu signal commencing of the trim management, a +22dBu signal are going to be seen at the amp's inputs. the sole place the signal ought to receive ANY quite gain is from the trim management. 

Again, another example...a +22dBu signal comes off the trim management. It ought to maintain this worth through the channel combining weight, the channel fader, subgroup fader, main combine fader, house EQ, crossover, and right to the amps. once the gain stays identical throughout the full system, this can be called a "unity gain" system. 

On every fader on most mixers, there'll be a "0" or a "U" mark(most Mackie boards use the "U"). Setting the channel, subgroup and master faders to the current mark can guarantee unity gain through the mixer. In different words, with the fader set to the unity gain mark, no matter is returning from the trim management can seem at the outputs of the mixer. 

On all PA gear, you've got gear that's either +4dBu or -10dBv compatible. Some items of substances have a switch wherever you'll switch it to either +4 or -10. This matches the inputs and outputs to the kind of mixer you've got. Most "consumer" gear is -10dBv whereas "pro" gear is +4dBu. during this tutorial we are going to be operating with +4dBu gear. 

Most +4dBu gear has AN input and output rating of +22dBu. 0dBu=0.775 Volts, thus +22dBu is roughly regarding nine.756 Volts. Mackie mixers even have a +28dBu output rating, but that is simply to convey you another +6dBu of headroom to stay from clipping the mixer's output stages. The Georgia home boy output from every channel's trim management is really +22dBu. 

Power amplifiers, however, have AN input sensitivity rating that's a lot of under that. The input sensitivity rating on power amps is that the minimum voltage needed on the input to cause the amp's output to place out full clean power. Most power amps have AN input sensitivity rating of regarding +3dBu-+8dBu. this can be why power amplifiers usually have input electrical device controls on them, that square measure the amount knobs on the front panel. a awfully common thought is that if you do not set the input attenuators all the far that you simply will not get full output from your amps. However, power amps square measure fastened gain devices...they will place out full power despite wherever the input attenuators square measure set, however, counting on wherever they are set, it'll simply take a way larger signal to push the amp to full power. deciding by this statement, we have a tendency to currently grasp that every one the input attenuators do is raise and lower the amp's input sensitivity. The input sens rating that's publicised within the power amp's user manual is that the sensitivity of the amp's input with the attenuators totally clockwise(all the manner up). this can be why they are there. I mean, for instance, parenthetically that your mixer is capable of swing out +22dBu of signal, nevertheless your most sensitive amp clips at +4dBu at it's input with the attenuators totally up. Well, currently you are sacrificing +18dBu of gain/headroom you'll be obtaining out of your mixer as a result of once your amp is at it's clip purpose...that's all you get. this can be why the input attenuators square measure there...so that you'll match your amp's input sensitivity to your mixer/crossover. 

The reason correct gain structure is very important is so we have a tendency to get Georgia home boy gain from the mixer, giving North American country additional dynamic range(headroom) and a lower noise floor. Georgia home boy gain from the mixer can increase your signal to noise magnitude relation, supplying you with higher seperation between instruments. It conjointly makes your channel EQs way more effective. I see lots of individuals use manner an excessive amount of boost from the combining weight itself than from the gain management. If you flatten the combining weight, then maximize the gain from the trim management, your combining weight are going to be way more effective to wherever on some instruments you'll ought to use cut quite boost, that allows you to induce even additional gain from the channel's trim management. an excessive amount of boost from the combining weight instead of from the trim can cause part distortion, which can darken, or soil your signal to wherever it nearly sounds buried within the combine. 

Following may be a piecemeal procedure for setting correct gain structure. you'll want a check CD with a pink noise track to try and do this. Pink noise is each frequency inside the human hearing vary vie simultaneously(at identical time). you'll transfer a full blown check CD that includes all types of check signals, together with pink noise, frequency sweeps, left/right test(to certify you wired the system so left is left and right is right). 

Test CD transfer 

Test CD Info/Track List transfer 

For this procedure, set all channel EQs flat, all channel Low Cut filters off and every one faders all the manner down: 

1) Play the pink noise track through 2 channels. Pan one channel onerous left and therefore the different right. 

2) Rotate the left channel's trim management right-handed till you see the channel's "Clip" or "Overload" indicator begin to return on, then back down till the indicator simply turns off. you're currently at the Georgia home boy gain setting on the trim. 

3) Repeat step a pair of for the correct channel. 

4) Set each the left and therefore the right channel's faders to the "0" or "U" mark. This puts the channel at unity gain and sends the complete signal from the trim management to the most combine buss. 

5) certify each the left and right channel's square measure assigned straight to the most combine buss. 

6) Set the most combine fader at the "0" or "U" mark. currently the trim control's full signal can seem at the mixer's outputs. Run this signal through your crossover. Set your crossover's input and output controls to the purpose wherever the input/output clip indicators simply begin to return on, then back down till they simply depart. If your crossover's Georgia home boy input rating is +22dBu(it ought to be), then it just like the mixer ought to be simply going into clip. 

7) With the speakers disconnected and therefore the amp's input attenuators totally counterclockwise, flip your mains/subs amps on. 

Rotate every input electrical device right-handed till the amp's clip lights square measure simply setting out to return on. 

*Note: Most amps that square measure bridged can solely use Channel 1's input electrical device and Channel 2's won't move. 

9) activate your crossover's inbuilt clipper and set the brink to it's highest purpose. Then slowly lower the brink to the purpose at that the amp's clip indicators simply depart. 

Your gain structure is currently properly set, and your clipper can shield your amps from going into clip. 

10) close up your amps and reconnect the speakers, then flip them back on. 

11) currently play a music CD of your alternative through the system, and listen. nearly always I realize that once the mains amp is ready to clip at precisely the same time because the subs amp, the mains square measure nearly always too loud, thus you'll need to show the mains amp input attenuators down additional to balance the mains to the subs. this can offer you even additional headroom on the mains amp. 

Now after you sound check your signal sources (i.e. instruments)...have every performing artist play the loudest that they're going to play throughout the performance. ensuring every channel's combining weight is flat at now, rotate the trim on every instrument channel till the clip light-weight simply starts to return on, then back down a hair. GET the maximum amount GAIN AS you probably will FROM THE TRIM CONTROL!!! this can be terribly IMPORTANT!!! Bring the channel's fader up to zero or U, then slowly bring the master fader up to performance volume. hear the instrument and apply combining weight if necessary, then reset your trim as expressed higher than. do that for all instruments. 

Set all channel/subgroup faders to the zero or U mark, then slowly bring the most error to performance levels. hear the general combine, if you would like additional of a definite instrument, bring the opposite instruments down around it. it is often useful to subgroup drums and vocals since they take up additional channels than guitars usually(especially drums). invariably keep the lead vocal channel and therefore the vocal subgroup faders at zero or U to induce the Georgia home boy signal from your vocal combine. Balance your backup singers to the lead vocalist. The drum subgroup faders can usually be regarding 5-10dB under vocals, counting on personal style. Then bring the stringed instrument and therefore the bass channel faders up to balance with the drums and vocals. 

Basically the secret's to start out with all channel/subgroup faders at zero or U, then hear the live combine, and produce down the faders on channels with instruments that stand out an excessive amount of. Drums and lead vocal channels, with the exception of snare, hi hat and overhead channels can nearly always occupy zero or U, then balance snare, hi hat and overheads to the kit. Then slowly bring the guitars and bass into the combination till they mix with the drums and vocals well. you'll ought to combining weight them slightly to create this happen.

To Summarize: 

Gain doesn't equal volume 

The amp's input attenuators don't management the amp's output level 

Always attain all gain controls for the foremost clean and clear signal from the supply 

Set the loudest instruments within the mix's faders to zero or U on the channel faders, then use the remaining faders to balance the remainder of the instruments to those instruments 

Control your overall combine volume with the most combine fader, not the channel faders.