You're not understanding exactly what the amp is doing and what the level/gain **** is adjusting. Like I said gain all the way up does not equal full power. You arent turning the amp "up" by turning the gain **** up. It is a level matching device, not a volume ****.
Im going to try to explain this as simply as I can. So bare with me.
Sound is a wave. Imagine a sine wave like from geometry class in high school.
http://lwosterman.members.winisp.net/sinewave.png That is what a sound wave looks like (roughly). Now, the distance from the top of the wave to the bottom, is its amplitude. Amplifiers increase this aspect of a sound wave, they make it bigger bottom to top. Makes it louder.
Essentially, an amp has 2 inputs and 1 output. 1 input is the signal from the rca. It is the soundwave at a very very very low level, the 2nd input is from the cars charging system. An amp takes the signal, and injects extra power into it, making it louder. If an amp is rated at 40 watts, that's all it can put out, 40 watts.
The gain **** is a LEVEL MATCHING device, it allows for differences from one radio to another on the input voltage of the signal. If you crank the gain **** all the way up, you are lying to the amp and telling it that it is getting a lower voltage signal than it is.
This causes the amp to attempt to add power to the signal, beyond its electrical capabilities. You end up with what is called a "clipped wave" or in extreme cases of incorrect adjustments "square waves"
This is what a clipped sound wave looks like (essentially)
http://www.geofex.com/effxfaq/d101_02.gif This is one of the things that causes audible distortion (along with speakers being played past their mechanical limits)
Here you have an amplifier that thinks it is getting a lower level signal that it is, it overcompensates, but it still has its limits (the top clipped off area) It amps the signal, but part of the signal goes past its amping abilities so it just sits there at it's absolute limit for the top clipped portion of the sound wave. The amp is sending as much voltage to the speaker as it can for an extended period of time. Anyone can reason that this is extremely ******* the amp and can quickly cause it heat up more than it should, and caused increased wear on internal electronics, along with pulling more voltage from the charging system than it needs.
A sound wave only makes sound in curved areas, you can imagine that that sound wave is also the path of a speaker moving in and out. It only produces sound when its moving. If it is sitting at the top portion of the wave, its not moving, but its still being sent a large electrical charge. Because the speaker is not moving during this time it also lacks the cooling the speakers coil gets during normal operation.
Will it sound louder? Yes, but only because parts of the wave are being amped more than they should. It will also sound distorted and will cause unneeded wear on both the speaker and the amp.
To CORRECTLY udjust gain/level, you need one of two things.
An EXTREMELY good ear, one that even most audiophiles dont have.
Or a dmm. Digital Multimeter, an analog one with a needle will not do the trick, it must be digital. You can get one at radio shack for like 12 bucks.
So after you get a DMM you will need a tone signal. If you are adjusting an amp that powers your main speakers, use something around 150hz. You can get this from here.
http://www.realmofexcursion.com/downloads.htm 150 hz 0db sine wave works great. Burn it to a cd and take it (and maybe some ear plugs) out to your car. Turn the volume on your headunit to around 3/4ths of the way up. Attatch the DMM to the positive and negative leads of your amp while the amp is connected to the speaker. And have it set to show voltage in the 100s or so, you probably have to adjust where the decimal point is.
Now there is an equation which comes into play.
The formula is "sq root of amplifiers rated rms watts x resistance(ohm load)
If you were using this amp.
http://www.edesignaudio.com/product_info.php?cPath=21&products_id=45 we would see that it is rated at 100 watts per channel, at 4ohms.
So. 100 watts by 4 ohm is 400 then we find the sq root of 400 which is equal to 20
We now know that 20 volts is equal to 100 watts into a 4ohm speaker. If you have a 2 or 6ohm speaker (you probably dont) you just change the 4 to a 2 or 6 of course)
So, find out what your amp's rated output is into the speaker you are using. Then do the little equation, figure out what voltage you are looking for. Have your headunits EQ's and sound effects stuff all flat and turned off. Put in the cd with the tone, put in the ear plugs, hook up the dmm to the amps output, play the tone and adjust the amps gain slowly up or down until the dmm registers 20 volts.
Honestly, all in all it takes all of 15 minutes. If you find that after you do this, its not loud enough? Guess what, you need a more powerful amp. You do not need to turn the amps gain up more.
Damn that took a while. Anything worth doing is worth doing right!
