Gains and headroom.

[TaylorFade 10+ year member]

I think I have a basic idea of what "headroom" is as far as a sub is concerned, but I get a little fuzzy when it comes to headroom when referring to an amp. I have never run my amps at full gain because I was under the impression that THD is directly proportional to gain settings. Is this true? I have also heard that using the maximum gain settings to retain all of the control at the HU is desirable. Which is it? And is running max gain and lower setting on the HU really for "headroom?"

Assuming that your sub can handle every bit of your amp- is there any advantage to running 50-75% gains?

And lastly, I read somewhere that 6db or more is a desirable amount of headroom. That would be like running 25% gains, wouldn't it?

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[DarkScorpion 10+ year member]

When you're setting your gains, you're trying to match the input level of your amp to the output level of your headunit. If you find yourself maxing the gains for ANY amp, you should invest in a line driver. Ideally, you want your gains set as low as possible, because as you said, higher gain settings will typically introduce more noise into your system, which you don't want. You also don't want to drive your amp into clipping by maxing the gains just because it sounds louder - it's not good for your equipment (there are tons of threads as to why/how clipping is bad) and usually sounds like garbage.

The % thing is completely amplifier dependent - the best way to set your gains is by ear. Some people will say it's better to set it by using a DMM and a test tone, but I promise you that you'll never be hearing a continuous tone while you're listening to music, unless you're burping. Usually by using the DMM method, your amplifier's gains will be set lower than they ideally should be.

Head room is good - by having head room, it's meant that your amplifier is pushing enough power to where your subs/speakers will not get any louder w/ more power - therefore, you don't need the amplifier to push its full power.

 

[RAM_Designs 5,000+ posts]

Amplifier headroom is just having more power than you really need so that you don't have to stress the amp and as a result keep the gains low and noise out. This can also be referred to as "dynamic headroom," where peaks in the music can be cleanly reproduced due to the extra clean power available.