fuse blows during amp install

I am installing a NEW Cuspid AM-4310 Amp in my cousins 91 Chevy. I have a 8 gauge wire running from battery to a 80 amp in-line fuse, then through firewall to amp. Same 8 Gauge wire grounded to the seat frame. then the remote wire, RCA cables to HU. BUT when i put the 15 amp fuse in the amp (same size came with it), and turn car on it blows the amp fuse. something i noticed too is that the amps power light comes on when the car is started no matter if the amps fuse is installed or not. I have yet to connect the speakers. thanks for the help.

and by the way, i know the amp is crap but he bought it and im just helping him out.

Disconnect the remote wire from the amp.  Does it still blow the fuse?     If not, there is a problem with the amplifier.  Probably has one or more shorted output transistors.   Or if it is a chip amp, it has a bad output chip.Let's Go Brandon Brown. Congratulations on your first Xfinity Series Win. LGBFJB

Yes

yes and no, originally i had a 4 gauge wire from battery, and a 8 gauge ground, and i blew once i put the wire to the battery. then switched all of the wires to 8 gauge, and no it only blows when i turn the car on.

The power light on that amp (and you're right it IS a huge POS) does not indicate whether the power supply within (if even equipped with a power supply) is functioning - it will only tell you that the remote lead is "hot". If you can, pull the bottom off the amp... I'll be dollars to doughnuts that there is no power supply... I'll wager there are two big ol' STK chips in there, with nothing but battery voltage on the power pins... A single 15A fuse? That's the same size fuse that most decks have in them... 50x4 MAX! I know, so far I have not answered your question, but from all appearances, I'm also betting that your amp is pooched.It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

yes it is disconnected and does not blow with ground and +12 ONLY.