Amp n pre amp

[Firefox]

Hi,

 

Thinking of adding a pre amp to audio that consist of amp. do I connect the o/p of the amp to the pre amp or the other way round?

 

BTW I observed that I need to tune up my vol abit more to get the bass when I have 1 amp to drive a component set spkr & another amp to drive apair of 2 way & pair of 6*9 spkr plus I have a active sub in my car in the set up also. Is there something wrong with my set up. Some suggestions was to add a cap to my set up b'cos not enuff power to deliver. Comments, advise & expertise anyone can enlighten me?

 

Lastly, I had another amp that face aproblem of turning on & off intermittently. Any advise on it or any recommendations that I can get it fix and roughly how much wld it cost.