Gain is not a volume control or power level control. Gain is a way to match the input volume with the output so your music is reproduced at the volume it is designed to without clipping. Until you determine the clipping volume of your source and the clipping output volume of your amp, you can’t really make any assumptions. SMD DD1 can help you with this.

 

The gain IS essentially a volume knob, it increases the voltage of the signal exactly like the head unit volume knob does. It is used to match the input voltage, so it isn't used the same way a typical volume knob is, but it's doing the same thing.

That said, OP if you have plenty of output with the gains at their minimum setting, there is no reason to turn them up. If after some level matching, EQ, etc. you aren't reaching the output levels you expect (especially on lower dB recordings) then you can turn them up, otherwise leave them at the minimum setting that provides the listening levels you want. The exception is if that ends up requiring you to turn the head unit volume up past it's clipping point. It's helpful to know about where your head unit clips and keep the volume level below that, use extra gain on the amp to accomplish that if necessary.

 

I'm betting you'll have to raise at least one of the gains after you cut the crap out of the hot spots.

 

Yes sir, I ran into this. I initially had to run my head unit volume to 80-85 % to get “loud”.

 

If it doesn't clip and it's loud enough your good to go.

 

nothing wrong with minimum gain set if you can drive your amp to max output potential

 

You'll want more "volume" once you start getting the car on the freeway. Road noise is a ***** and it WILL kill some of your sound. Or, you'll get used to the output and want more.