There are two ways to run sound for a band and it's important to decide up front which one your looking for. Is it going to be Big Sound? or Sound Re-enforcement
PA systems are often referred to as Sound Re-enforcement systems. What that means is they are used to assist the sound being made on stage to fill the room, bring out the quieter parts, and basically build up the tone a bit.
In this situation your Guitar amp is the primary driver of the guitar's sound and the only reason it needs to be mic'd is if it's not quite up to the task. and even then the PA only beefs is up a bit.
All of the amps are placed pointing toward the room and the band provides their well rehearsed mix (see 'Top Priority) to the room. the PA is mostly used for vocals and adding a little kick and balance.
This is a pure and true example of the kind of sound a band is able to put forward, and if the band is good at what they do, it works very well. The audience is then treated to a wide sound stage in which each instrument sound comes from it's own position. Properly done this can be very exciting
Big Sound on the other hand is where you mic or DI everything and put the whole mix into the PA so that what come out is the same thing you'd hear if you were recording a CD.
Once you've decided your looking for Concert sound and have a big PA with big subs and big power. (this means that the PA dwarfs the guitar and bass amps combined, if your using a pair of speakers on stands then you'll get better results using it as re-enforcement) Then the sound guy wants to get everything into the mix, and mix as though making a CD. if fact when you play back the recording it should sound like one.
Use headphones so you can isolate your mix from the room sound. If the Guitar is quiet in the headphones then bring it up. "But in the room the guitar is too loud" This a problem for the guitar player not the PA. Tell them to turn down. Assure them that your driving the room and that they need only drive the stage. (refer to 'Top Priority') Even so, by bringing them up in your house mix, your not making them sound louder, just bigger. Sometimes by bringing them up in the big PA your waves can overpower the guitar amp's and smooth them out and result in making it not sound so loud.
Remember, your trying to make the sound Big not Loud
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