Car audio- Fuse keeps burning out

[leatherlips]

I have a car audio setup I put in about 5 years ago. All worked well up until recently. Suddenly the main fuse (near car battery) blows after running for about 15 min (or so). The Amplifier fuse does not blow.
The fuse in the amp is 40amp. it's a 400w 4 channel amplifier. The fuse near the car battery was an 80amp fuse. That's the one that burnt (not the 40 on the amp).

I'm wondering if anyone can point to what might be the issue. BTW, I replaced the amplifier and it still does the same thing. I'm assuming it's got to be in the main wire from the battery to the amplifier (not any of the speaker wires), but not sure if that makes sense.

 

[NL5]

My guess is somewhere between the battery and the amp the insulation is worn through just enough to blow your fuse.

 

[pcgeek11]

I agree. You have an intermittent short circuit on the wire between the battery and the amplifier. Probably where it goes through the firewall into the passenger compartment.