Here is the story:
For over a year I ran 2 subs off of a 200W Optimus amp. I then upgraded the sub's amp to my PPI amp, and used the old 200W Optimus amp to power my 4 coaxials. I ran the line level signal from my Aiwa HU to my PPI amp, and then let the PPI amp feed just the highs to my 200W Optimus amp. I then upgraded my subs to my DDs. For awhile I was constructing a new box, so I took out my PPI amp and ran the line levels straight to my Optimus. After awhile of that, I'd start getting clicks and pops, nothing major. Then one day while listening the amp opened up FULL PINK NOISE output to all my 4 coaxials! Volume control didn't do anything, neither did switching to FM, or even an empty AUX INPUT. The only way I could shut it off was to turn off the deck completely. Mute didn't stop it either. This happened a few times, more and more frequently. Each time I could smell burnt coils from my coaxials, but they never blew suprisingly. Finally I put my PPI amp back in, and fed the signal path through it again before letting it into the Optimus amp. I hooked up my DD's, and was terrified that my deck would "burp pink noise" again, and destroy my new DDs. Ever since the signal has been going through my PPI amp again, this "pink noise burp" hasn't happened again.