Ima start off by saying that the cd/DVD player hasn't been working for over a year, the headunit is 3.5 years old it's an alpine iva-w505. A few days ago I had the heater on with the radio on mute for approx 45 minutes then I turned up the volume and it sounded like crap: high pitched highs and lacking vocals. Ive ran the headunit in defeat for ever which turns off all eq and the amp is hp at 95hz 12db. The next day the system sounded better but I don't feel like it sounds as good as before. Is the headunit fried? What's going on?

Front speakers: focal k2p; 3.5 years of use
Amp powering: jl hd 600/4; 150 rms; 2 years of use
Headunit: alpine Iva-w505; 3.5 years of use

 

You may be able to isolate the problem by alternating sources. For example FM radio. If the radio is good then the problem is the head unit.

If all sources (radio - auxiliary input) are bad I suspect the problem is the head unit or power amplifier.

Here I suspect that the problem is the pre-amplifier built into the head unit.

 

...

 

turns out I have a bad channel on the amp.. so I'm temporarly using the rear channels for the front stage and it sound normal.