A>B>C

A PA system contains three basic elements:

• [A] The signal source which can be a microphone, a tape deck, a CD player, an electric instrument, the Line Out from an amp, the output of another mixer or basically anything which produces an audio signal
• [B] The amplification stage which includes the preamplification (mixer) stage
• [C) The speaker system.

At all times the basic signal path is from A to B to C. To make the term "signal" a little more graphic, think of electrons. The signal source produces a small quantity of electrons. The amplification stage then adds many more and the speaker utilizes this enlarged amount of electrons to create the physical motion which produces sound.

This A>B>C concept is worth keeping in mind because each stage after the signal source has a certain maximum capacity. In mixers, power amplifiers and preamp devices this is called headroom and in speakers it's called power capacity. Try forcing too many electrons into something and you exceed that capacity, usually with audible results such as distortion or blown speakers.

"Clip" indicators, such as LED's, help you to prevent distortion by telling you when a circuit in a mixer, signal processor - reverb, EQ, etc, - or a power amplifier is on the verge of being overloaded. Unfortunately there is nothing similar for speakers. They simply distort and/or self-destruct unless they have fuses or circuit breakers built in.

As mentioned above, the PA process begins with a source signal. The source can be any one of many different things from an electric instrument to the line-level output of an instrument amplifier, a tape deck or CD player or the output of another mixer. But the microphone represents both the most commonly used signal source and the one which requires the most understanding