Stereo Set Up, Gain Set with Loudness On

yesterday i finally had my stuff installed with a help of my friend's friend, who's luckily, custom audio guy. turned out my jvc hu only had 1 rca output, so the rears, and the fronts run on one cable (how significant is the sound quality loss because of this?) also, i noticed that he set the gains on "loud on" in my hu. is it a standard procedure, or does it really matter? thank you.

If you are planning to use the loudness control, then yes your amplifier gain should be adjusted with this function turned on as it boosts certain frequencies and can drive your gear into clipping otherwise.Support the12volt.com

that's the thing...i don't like to blast my music, just something clear, and punchy. i was just curious if the "loudness" compromises the sound quality. as you can tell, i have no idea how it works.

also, about the preamp outputs...that guy told me that if i were to buy a new hu (recommended pioneers), i need one with 3 sets of outputs (front/back/amp) which is a bit different from this set up: http://www.crutchfieldadvisor.com/S-wIJ6e8hwoNN/learningcenter/car/amplifiers_wiring.html also, seems like most hu come with two, so i'm curious which set up did he have in mind...

He's just steering you toward a deck that has features you can use.  And no, don't use the "loudness" control unless your mother-in-law is in the car and the volume is so low you can barely hear it.  Soon as the volume gets to a halfway respectable level you should lose the loudness compensation.

Also, yes, loudness does alter the music and compromises the sound quality. New Project: 2003 Pathfinder

cool. will have to reset the gains with loudness off then. also, this is weird, because i looked up the info for my deck, and it does have 2 sets of outs. that's what i thought to begin with, but this cat tells me there's only one. i asked him what was the other one for, and he couldn't quite make it out (he doesn't speak much english, so we had poor communications). that's my deck btw: http://www.crutchfield.com/S-sTJy9cOy6Ld/cgi-bin/ProdView.asp?g=300&id=features_and_specs&i=257KDSX990 good thing i ran the other rca "just in case". not sure why he said it was only 1 preamp, since he's a professional installer and all... and also, could someone explain me the difference between running fronts/rears on 1, and 2 rca's (respectively)? signal-wise, and how does it affect the sound quality.

anyone...

will do that. thank you.