1200W+ AMPS SENDING DC TO SPEAKERS, I need help Options

[Kamakaze]

Ive done a few installs and Ive seen this problem about 4 times, where the amplifer sends out DC to the subs and ends up burnin out the sub. Ive tried alll i can think of but heres my history.


1st It was a KICKER 650 amp with Kicker L7 subs
-----changed the amp out to a Swiss Audio AmP, this was a much bigger amp and it sent even more DC voltage.
-----then changed a Pioneer4800 headunit to the pioneer N3 (that didnt solve anything
Then I decided to change out the subs (since those got burnt out) and added two L7's) still a problem so i left that project alone before i blew those too.

Next car had the same KICKER 650 amp with an L5 sub
------the subs got burned out so i changed the amp to a Kenwood 1800W that kenwood jus wasnt working period, took it backk and got another one and this one is now sending DC

if anyone has a solution please let me know ASAP.