My sub plays everything

well you have two problems...

1- you paid money for a legacy amp -- thats like buying a sack of magic beans.

2- you need to utilize a crossover (low pass filter) to only allow the bass to run to the sub.

you can fix the crossover problem in a few ways...

a) if the amp has a built in crossover, engage it, turn it to "low pass" or "LP" and if it has a dial for the setting, set it to about 90 hertz.

b) if the head unit (radio) has a built in electronic crossover for its pre-amp outputs then you can engage it there, and set to low pass... anything between 80 and 100 hertz should do.

c) if you have no crossovers at all then you can either spend 20 bucks on a set of Harrison Lab's FMOD inline RCA crossovers or you can get a simple subwoofer crossover network from crutchfield for about 30 dollars that will hook inline with hte RCA's and hack out all but the bass. this is the better choice since then u can have more options than with the Fmods (no options at all - preset).

d) since you're running under 35 volts AC parts are easy to find and you can build your own crossover network, but i really would not advise it for you... besides, now that i think of it, it may be a **** to get low pass stuff for 100 hz. high pass is cake but low might be a bizzzatch. i'm too tired to really think about it tht much. but try to do a/b/c ... those are u best bets.

well 85 hertz would be the goal but i think they jump from 75 up to 100...

are u sure the amp doesn't have a built in sub crossover?

check... look hard... if u're 100% sure u cant fix it with what you've got, post back and i'll find you something 'simple' and in the 30 dollar range to solve the problem.