Amplifier Gain Switch Question

I installed the Alpine KTP-445 Head Unit Power Pack in line with my Alpine IDA-X305s HU a couple of weeks ago and it has a selectable gain switch (high/low) on the back. My question is simple: what does it do? I'm somewhat knowledgeable on the car audio stuff, but not on these sorts of details. I don't even remember what it is set on. I just left it how it came in the box. (Low, maybe?) Note that I'll soon be upgraded to some component speakers in the front and 2-way coaxials in the rear doors.

My second question is related to my speakers that just came in the mail. I picked up some Infinity Kappa 52.9i 5.25" 2-way speakers for the rear doors in my DC. The tweeter on those Infinity speakers has a button for 0db or -3db. My question on that one is simple too: what does it do? Does that merely subtract volume level from the tweeter so that you can fine tune the speakers to an optimum tweeter and mid-range mix?

Thanks for any help on these two questions folks. I might be getting started on my big sound deadening and speaker upgrade Sunday. When I do I'll be sure to take pictures of the process.

 

TTT

Bueller...Bueller?

 

For the input sens switch on the amp, it basically lets you select what type of voltage you have coming into the amp. If you're using speaker level inputs then you would use high. If you are using RCA's then it should be low.

The tweeter switch for the infinities is for tuning. Some like it hot, some like it cold, so if you like your tweeters hot keep it higher.

 

Great! Thanks IS. I thought of PMing you directly, as I thought you'd know.

I'm hoping my front components are waiting at my doorstep when I get home today!