i am trying to build a circuit that will have a light that brightens to the bass in my car audio. i don't want to use db sensors because they pick up all noises and i just want lighting to change to bass. i was thinking of using the varying ac audio signal that goes from the amp to the subs. the signal ranges from 0vac(no bass) to 40 vac (subs are hitting with greatest db readings). i could use the amp to power ac lighting but that would divert power from the subs and the apms efficiency will decrease. the leds will be powered from the cars battery. every circuit that i think of will just turn on and off. my first though was to use an scr. the gate will be turned on by the signal reaching some level set by a reostat allowing a 12 vdc current to flow which would power the lights, once again i believe this circuit will just turn on and off. i want my lights to dim and brighten to a 0-40 vac signal. any ideas.