Part 1
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PA Systems come in many different shapes and sizes, ranging from the very elaborate systems used in large stadiums all the way down to a simple microphone patched into your home stereo. Listed below are several of the most common setups.
An easier way to think of it might be to think of it as a river, the microphone being upstream, the speaker being downstream, and the amp being a reservoir in between. As the water (the signal) flows from upstream (the Microphone), it must enter the reservoir (the amp) through an input, and then exit the reservoir through an output until finally, it reaches the downstream side (the speaker).
So, that's the theory (complete with a picturesque metaphor). Now here is the reality. In the example above, you would plug things up in this order.
1)Plug the mic cord into microphone (There is only one place to plug it in. Technically it's an "output").
2) Plug the other end of the mic cord into the "input" of the amplifier (remember, input is coming from the microphone).
3)Plug the speaker cord into the speaker "output" of the amplifier (the signal is flowing out of the amp toward the speaker).
4)Plug the other end of the speaker cord into the "input" on the speaker (the signal is coming from the microphone through the amp to the speaker.
And there you have it. You have successfully hooked up your first basic PA system. Of course, although it will amplify the sound, this particular system won't be of much practical use to you in any real life playing situation. It still lacks three essential ingredients.
Keeping in mind signal direction, the system shown in example 2 should be hooked up like this:
1)Plug the mic cord into microphone (only one end of the cord will fit).
2) Plug the other end of the mic cord into any "input" channel of the mixer (input comes from the microphone).
3)Plug a high Z cable (patch cable) into the "main out" of the mixer (the signal is flowing out of the board toward the speakers).
4)Plug the other end of this cord into the "input" of the equalizer (the signal is flowing from the microphone).
5)Plug one end of a high Z cord into the "output" of the equalizer (the signal is flowing out of the EQ toward the speakers).
6)Plug the other end of this cord into the "input" of the power amp (the signal is flowing from the microphone).
7)Plug two speaker cords into two speaker "outputs" on the power amp (the signal is flowing through the amp toward the speakers).
8)Plug the other ends of these cords into the "inputs" of the speakers (the signal is coming from the microphone to the speaker).
Warning: Never plug anything other than a speaker into the output of a power amp. A "speaker out" connection carries a very strong signal that can and probably will cause damage to the other components. |
You may have noticed that you have more than one channel in some (or all) of the components of your system. These are usually labeled in one of three ways; A and B, 1 and 2, or left and right. Each or the two channels will have its own inputs and outputs. What this means is that the component is stereo. Basically that means that it contains two completely separate pathways for two completely separate signals to flow through.
The system examples so far, for simplicity's sake, have been mono systems, but the principles are the same for stereo. A stereo PA can easily be used as a mono PA by simply running through only one channel in each component. For instance, If you wanted to use only channel "B" in your EQ, you would use the input and the output for channel "B", and leave the channel "A" inputs and outputs open. Of course, when you actually use the EQ, you have to remember which channel you hooked up so you can know which one you will need to adjust to change the sound of the PA. Moving the channel "A" knobs won't do anything if only channel "B" is hooked up.
The sound board is a little different in that you need only be concerned with the outputs. There are many inputs in a soundboard coming in from the many microphones on the stage, but a stereo board will have two separate "main" output channels. You need only choose one of these to use it in mono. Just remember which one you choose and adjust the knobs on the board accordingly.
The real draw back to running your stereo PA system mono is that you end up using only half of that expensive piece of equipment you bought. That isn't that big of a deal with an EQ or a crossover, but with a power amp, only using one channel means you only use half of its power. Only using half of a 500 watt amp results in only getting 250 watts of power, and that just plain sucks. This problem can be fixed by the use of "bridging", but it's a variable and sometimes complicated setup that can be hazardous to the health of your equipment. If done right, it's great. If done wrong, it's disaster. Therefore, I've decided to leave bridging out of this tutorial (liability and all). However, I did find a complicated technical description of it on the Peavey homepage. If you are interested in bridging, try looking there. If you're not, just do what I do and keep on truckin' without it.
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