I just got my 1000W plate sub amp from parts express and my yamaha 1500 doesnt seem to want to turn the amp on and off when the switch is on 'auto'. The amp just stays on and I have to shut it off with the switch. Any ideas? Also when I shut the amp off (after receiver is shut off), the subs make a sound for a second, not real loud but loud enough. ANy ideas on this? Thanks!