Basic Training for Sound System Operators
Articles from Pro Comm's Quarterly Newsletter
Mixing it Up: The Fundamentals of Mixing
Reprinted from "Sound Advice"
The first task for the mixer is to amplify the very low output of any microphones being used and balance them with any other components such as background tracks from tape decks or direct inputs from instruments. This is the first question that usually comes up: How do I know where to set the volume (level) controls when starting from scratch? Every mixer or mixing console has an optimum position for each individual channel level control and master output level control(s). If set accordingly, the mixer performs at its best. The first place to check for this type of information is the operator manual. 

If no manual is available, the following guidelines offer a good starting point. 

1. Look for an indicator on each level control such as a heavy white line or hash mark. If your mixer has fader controls (sliders), then look for the zero dB point. Usually this point will have positive numbers above and negative numbers below it. If your mixer has rotary controls (knobs), determine the full rotation of each rotary pot. The best starting position will be 1/2 to 2/3 up; on a scale of 0 to 10, about 5 or 6. 

2. With all the individual channel controls fully down in level and any tone controls (EQ) set flat (no boost or cut), set the master or main output control(s) to their optimum position. 

3. Next, choose the primary channel (usually the pulpit mic). Bring up its level until the sound level is reasonably sufficient; don't over-amplify the mic beyond a natural level of reinforcement. If your mixer channels have input gain or trim controls, check to make sure they are turned up halfway for starters. 

4. If the resulting position of the channel control is barely on and the sound level is too loud or distorted, reduce the input gain/trim controls or if reducing this control does not compensate enough, reduce the master level control a bit. 

5. Neither the individual channel controls or the master control(s) should be too high or too low. You should allow yourself plenty of room for smooth gradual fades or increases in level. 

6. After you have adjusted the first channel to a fairly good position, choose the next channel and repeat the procedure until its level is in the same general position as the first channel control (they don't have to be identical, just fairly close.) 

7. You will find that as you add more channels, the overall system gain will increase; compensate with master output control(s). Also remember that the potential for feedback increases with an increase in the number of microphones on at any one time. 

8. If, after you've finished this procedure, the overall system level is still too loud, reduce the level control at the appropriate power amp. Before doing this, check to make sure that any other devices between the mixer and power amp (an equalizer, for example) have their input and output level controls set to approximately half-way (unity gain if possible.)