Can someone please explain clipping

I've searched for this here, but all the references I came up with just gave mild mentioning of "clipping" with vague descriptions.  I know what clipping of a signal is by chopping off the top of the waveform and how that can affect a speaker by sending a temporary DC signal on each half-cycle of the AC signal.  This can almost look like a square wave.  All that is the technical definition. 

What I want to know is are we talking about clipping here.....the input signal to the amp from the deck's RCA outputs, or what the amp puts out to the speaker, or maybe both??  Also, and what specifically causes it(again, I know turning up the volume to max can do it, but how??).  Also how can the amp's gain affect this??  I was told that turning up a gain is actually turning down the voltage(I had this discussion in another forum about bad sound from an 8" sub.  I mentioned turning down gain, and they said turn it up instead). 

WARNING TO ENGINEERS: "Laymens terms" description ahead.  Do not cringe. 

An amplifier is an electrical or electronic device that uses a small voltage to control a larger voltage.  Small voltages (like the signal off a CD) are used to control a larger voltage in the head unit to create the line level signals.  This is called a pre-amp.  These larger voltages are then used to control an even larger one to create the speaker level signals.  This is called a power amp.  Both amplifiers work in pretty much the same way, and both can clip.

For a very gross physical way of visualizing this, think of a garden hose with a nozzle on it.  You and the nozzle work together as an amplifier when you control how much water can come out of the hose.  You are not creating the water, it has to come from somewhere (like your house, which is car audio terms would be the alternator and battery) but you can control how much is squirting your lawn at all times by twisting the nozzle or opening and closing the valve.

Just like you and the nozzle, an amplifier does not create anything.  It controls or regulates a larger voltage.  Other circuitry inside the equipment (called the power supply) makes sure the large voltages are available.  Sometimes these voltages come straight from the main power source (like the battery) and sometimes they are generated in the power supply through a variety of electrcital and electronic means to be much higher than what the battery can provide.  The ratings of amplifiers are determined by the maximum output voltage it can make available along with the maximum current flow that can safely pass through the amplifier circuit.

Clipping is what happens when the amplifier tries to put out voltages higher than what is available from the power supply.  Once the input (the small voltage) demands 100% of the available supply voltage, the output cannot go higher.  It is possible and very common, however, for the input to greatly exceed the 100% mark.  When this happens, the amplifier circuit says "OK, you want more, I'll open up my nozzle wider."  But if you've already hit the max your power supply can give you, or if the valve is already all the way open the flow cannot go higher no matter how hard you twist it.  You can only get the maximum the supply has available.  This in effect means the output during the clip remains constant at this maximum value.  Constant voltage is called DC (direct current.)

DC is bad in the sound world for many reasons, but it is especially bad for loudspeakers.  Basically it means the speaker stops moving during the DC part of the signal and all the power being supplied to it generates heat.  A speaker makes sound by moving and DC sounds bad, and a speaker cools itself by moving, so DC keeps it from being cooled.  The ultimate result is what Rob at Forbidden calls "SSS" (smelly speaker syndrome.)  Severe clipping can also cause the output amplifier circuits or the power supply to become smelly.

The "gain" or more accurately the input sensitivity control on a power amplifier is only there because there is no universal pre-amplifier level standard in car audio.  It is unfortunate in many ways because it enables novice users to easily destroy their gear.  It is also a very powerful control because it allows knowledgable users a lot of flexibility in their equipment choices.  Regardless, what it does it set the amplifier sensitivity to the maximum expected "small voltage" input signal.  If the gain is set so that the amplifier will reach maximum output at the same time that the input signal reaches maximum, this is called "unity" and is in general the ideal setting for the control, but any value less than this setting is safe to use.  If, however, there is a level mis-match so that the input signal can exceed the maximum expected value (for example, your input gain is set to 2 volts but the HU can actually generate 4 volts)  the amplifier will clip before the input signal reaches 100%.  This is bad.

When you turn the gain setting "up" you are actually setting the amplifier to expect a lower input voltage.  If the setting is off from what the input voltage can actually achieve, clipping is the result.

I hope that helped.  If not, here's some links.  Read Here, Here, or Here.

I will check the links out that you posted later.  But for now, what I get out of this is that the gain is like a valve that lets in so much voltage(in very basic laymans terms).  But the way I am reading this it's like saying if the gain was set too low......then the input signal would clip(and I get that because the voltage input would be higher than the gain would allow and therefore clip the wave peaks off).......but if it was set too high or wide open, then it would be OK because the input voltage is less than what the amp was expecting to see.  Therefore the input signal would never be clipped.  I know that part is not exactly right, but I can't see it in my head how it's supposed to work.  I know there is such a thing as too much gain.

You said this(sorry I don't know how to put it in a box):......."If the gain is set so that the amplifier will reach maximum output at the same time that the input signal reaches maximum, this is called "unity" and is in general the ideal setting for the control, but any value less than this setting is safe to use"........end quote.

Any value less than what??  The amp's max output??  That's the part I'm not clear on.  I guess I need an example there too.  Like say the gain is set at....oh....6 volts, and the HU can only generate 2 volts.  What then??

The way I read that is like the amp won't put out it's maximum if the gain is open way higher than the input voltage will be coming in. But at least it wouldn't be clipping.   And if that's true, then maxing out a gain wouldn't hurt anything.  I've always been told to NEVER do that.  If anything, keep it set low.  Of course, this was not a tech way to set the gain, it was just supposed to be a safe way.

Wow.  Several misconceptions to address.

First, like I said any amp can be clipped including pre-amps.  If a preamp clips it also produces a DC signal which is also bad for your gear.

Second, you have to watch what you mean when you say "gain set too low" or "gain set too high."  If what you mean are the relative settings on a car audio amplifier with "low" meaning turned counterclockwise and "high" meaning turned clockwise, then I think I follow.  Here is what that generally means.  Counterclockwise sets the amplifier input signal for a high pre-amp voltage, and vice versa.

Without getting into electronic theories and describing slew rates and gain slopes, etc. let me just say that what the "gain" control is doing is determining how much voltage is output for a given input.  An amp has the capacity to "put out its maximum" no matter where the control gain is set.  It can output maximum voltage at every point in the input gain range.  It depends on what level of signal is coming in.  Like I tried to explain before, if the gain setting is such that maximum output is attained with a 2 volt input, then that is what will happen.  When the pre-amp sends the amp 2 volts, the amp will output its max.  If the preamp sends 2.1 volts, the amp will clip.  This is what you mean, I think, by keeping the gain "down," meaning turned counterclockwise so the amplifier can handle higher voltage inputs before clipping.

What I mean by "any value less" is less than unity.  Less than the max the head unit or pre amp can produce.  Setting the input gain at 6 volts for a HU that can only produce 4, for example, means the amp will never be driven into clipping.  It does not mean the HU cannot be clipped and thus still destroy your gear, only that the amp is set to a safe operating level for the particular set up you have.

And lastly, "maxxing out" a gain control, if what you mean by that is turning it all the way clockwise, would set the amplifier for, say, a 0.2 or even a 0.02 volt max input.  This will almost certainly guarantee clipping at any volume level with today's head units.  This should not be done.

Is this more clear?

OH MY GOD!  All the years I've had amps and never understood even how to use a gain control correctly.  What have I done?? 

You mean that turning a gain control clockwise is actually narrowing the voltage that can be input from the HU??  And counterclockwise is widening the range??  If that is so, then no wonder you can start at the fully counterclockwise position, and the farther you turn it clockwise, the better it sounds as you approach "unity", until you pass it again, and then it sounds crappy.  NOw I know why I had to seemingly MAX out the gain on my Punch amp to get it to perform the way I thought it should.  I am using a Pioneer DEH-41 deck and I've been told it should output about 2 volts.  I've got the Punch amp's gain set at about 3/4 turn clockwise.  I set it by ear listening for distortion and that's where it ended up. 

Your example of sending 2.1 volts to an amp set to receive only 2 volts, would not only cause the amp to clip the incoming signal, but clip the output signal as well.  It would have to since it never received a good signal in the first place.  Therefore widening the range of the input voltage will decrease this likelyhood.   But you could push the amp into clipping by turning the deck's volume up way too high and sending a clipped preamp signal before it ever gets to the amp.  So we would be back to a clipped preamp signal, but not because the amp's gain was set too narrow, but because the deck clipped it first before it was ever sent on it's way down the RCA highway to the amp.  Right??

But what will happen if it is mismatched with the amp set to receive a higher voltage and it never does??  Assuming of course that you do not push the HU into clipping with the volume first.  I know the volume of the amp's output would be reduced somewhat, but why??  That's what I really want to know right there.  What will happen if it's left in a safe gain setting, and the head unit is never pushed to clip to start with.  Just low volume?? 

I'm so close to understanding all of this.  Thank you for your replies.  Everything else is seeming to make sense.  I'm just curious about that last point.  Thank you again.

Don't ever be sorry for going a bit further.  I do it all the time.  I responded to another post 4 times before he could respond back.  The more info the better I say, as long as it's right.

An amplifier's input gain setting will have nothing to do with whether the incoming signal gets clipped or not.  That would be caused by the head unit pre amps.

"audeogod," I really find it hard to believe that you could possibly get what your "oh my god" message states from my postings.  If you're trying to be funny, fine.  I don't want to play that game and please take it elsewhere.  But if you are being serious, if you really don't understand gains, and if you really believe what you wrote, then you have a lot to learn and I suggest you do so before you try to give advice to anyone else. 

This is not a flame, it is my dismay after reading some of your other well-written posts.  Is someone else using your login name?