Loss of Amp Power? possible

I am running a 10" Bravox UXP10 D-4 Subwoofer in a ported box in the hatch area of my corvette. Powered by a Mono Pioneer  400 Watt. Friday ,the Sub seemed to get quieter and softer. Believe me, this thing in the back of a vette is just on the edge of stupid. It has always rocked and hit hard no problems. I pulled the sub out and check Ohm Resistance on both voice coils with a meter and they are right on. Sub = O.K.  Now what?. Is it possible my Sony head unit (CDXM8810) is not sending the proper 5 volts through the Sub out RCA's to the amp input?? How can you measure the output voltage of the RCA's coming from the Receiver to the amp. I tried a meter on D/C voltage and got no reading. I can adjust my sub by going through the menu on the head. Its always been set on 0 DB. I had plenty of headroom for stuff like Rage against the Machine. Now its softer and when i raise it up it gets muddy.  It used to shake the car so much that sometimes i had to turn down the volume so i could make sure i didnt Blow the  Engine. Can a Amp slowly lose power and still work?? Any suggestions on a replacement amp to use?? Please help. I can see the cars in the rear view mirror now.  SPINJSpinj

[QUOTE=redpeppers]

i have checked voltage on RCA signal by running a single sine wave likr 35 htz for example and turn ur meter to the aC voltage side.....

How can i get a sine wave of 35 Htz out of the receiver to check.

                                                                                 JS

Spinj

I have a kewl Program for my Palm Pilot Tungesten T5 that allows me to generate sine waves,square waves,triangular, saw tooth, impulse, pink noise, and white noise at varying amplitudes. I use a small Fm transmitter from radio shack and I can test any system with an Fm radio. Its great for setting up electronic crossovers.

that is a damn cool setup sneaky. I've used this to create tones and burn them to a cd. Works prety well; but it takes a bit of time.Life moves pretty fast; if you don't stop and look around once in a while; you could miss it.