Understanding Signals and clipping

[Watt'sInUrTrunk]

How many times have you heard people say they set there gains by ear, a few I'm sure. Yes, this is OK for an average low wattage DIY system. But if you are going to step up to a serious system, set your gains right. Hears a little info to help you understand why.

What we have below is a series of three traces followed by a forth with all three overlay-ed on each other for comparison. For discussions sake lets say these are the RCA pre-outs on your head unit. The first trace would be at half volume, the second trace would be max volume point before clipping and the third trace is with the volume all the way up.

Let me make on point why a signal clips. Every amplifier whether its a preamp on a head deck or your 10KW monster has a maximum voltage it can deliver. This is the point it will clip at if the input voltage is to large. Thus is the reason we have gain settings. In the figure above, the first two traces are clean wave forms within the amps ability's. If we set the gain too high, it will attempt to amplify the input signal past its peak output level. In our example here that output is 2 volts peak to peak. Look at the orange shaded area of trace three, any signal past this point will be "Clipped" off. Now our signal is starting to look like a square wave and not so much a sine wave any more, :-/ this is bad. Why? Square waves have resonate frequencies not just there fundamental frequency. I'm not going to go into that here, if you want to know more about fundamental and resonate frequencies, Google it. One other thing to note, look at the shaded areas under each trace. As a signal is amplified its amplitude increases(the height of the signal) along with the area under the trace. Think of the amplitude as the volume level, there directly related. The area under the trace is power being supplied to speakers. If you try to push an amps' gain past this point there will be no increase in volume, the amplitude shows this in trace 3. But the area still increases. Look at the fourth trace. This increase in area under the trace equates to more power being dissipated into your speakers and amps to no benefit other then more HEAT. Also this can increase the current draw of your system. So, take the time and set your gains right. If you can't buy, beg, plead or borrow the proper equipment play it safe and set them way below any audio-able distortion.

Well that was my two cents. Hope you enjoyed and learned something.