I need help w/ new amp and bandpass box

I got a new Dual XAF460 amp and Dual XiNBp212 Bandpass box with 2 12's in it. I put it in a 93 Ford Explorer with a JVC head unit. The head unit does not have RCA outputs but the amp comes with high level speaker inputs and wiring harness built in. The instructions that come with these are probably the worst I have ever seen for anything so I had to call the Tech line probably 15 times while installing. I got everything wired and powered up without a problem until I tried to turn on the system. Tech said to splice into the rear speaker outputs for the high level output  wiring to the amp, but when I turn on the system I get no sound from anywhere. I can unplug the high level plug from the amp and the regular speakers come back on and play as usual, then when I plug the high level plugs back in to the amp I get the subs working again. Then anytime I tchange the song n the cd or change radio stations it shuts down again. The tech support at Dual says, " Hmm, never heard of that."

The high level input electronics in an amp of that quality is poor at best.  I would never use the built-in high level on any amp, but use a separate line out converter, like the Peripheral P-15.  If your head unit is rated at no more than 20 watts/channel, use the P-8 for best S/N ratio.  You can attach the LOC at either front or rear original speaker wires.  The solid wires are +, the striped wires are -.  RCA's plug into the LOC and go to the amp input.  Save yourself more headaches and get the LOC.