I have a 60 amp alternator and 140 rms amp on it drawing what I would equate to a 20 amp draw. Now what doesnt make sense is that the alternator I have is a 60 amp and was only a year and a half old and from the nissan dealer. I was using a dual chamber abc box and it was very sloppy in car but I straightened it out with a 18 db per octave crover on the amp. Now the strange thing is I had to turn the low pass filter almost all the way up to make the bass tight and believe me it was. My bottom line question is since the amp would technically clip without the filter set the way I had it was I just masking it and causing a very hard draw on the alternator with a horrible signal of some kind and that blew the alternator? I know you no your stuff so your insite is appreciated.
The signal would have nothing to do with the Alternator. Only way you could really kill an alt is if you were drawing too much power, and it couldn't keep up with the demand and burned out, or if the batter was dead, or almost dead, and the alt couldn't supply power and charge the battery at the same time.
Even if your amp was clipping, there's no way it was drawing enough power to overwork the alternator. A 60 amp alt is pretty small, but still, 140 watts rms shouldn't be that that big of a strain. That with the demands of your engine and other components, plus your amp, that the alt couldn't keep up. I find it unlikely though. I think you just had a bad alt.