02 ls430, system melting loc

so i took the car to this audio spot to install an amp and a single sub in my ls430. the first 10 minutes we smelled something and pulled over to check everything over. seemed fine kept driving listening to music and everything was fine. today i drove around with the music on and stunk again and the box wasnt pumping. took the car back to the guy and he found the line output converter was melted and installed another one. this one worked for 15 minutes and now i have no more basss. whats causing this? is this guy doing something wrong? he changed the signal the second time for the converter so it would get it from another spot. could it be the ASL feature that adjust the cars volume while driving? this is really frustrating!!!

from what im reading i think the shop used a cheap LOC and it couldnt handle the signal coming from the mark levinson amp. would i be alright with a 80watt LOC like this http://www.bestbuy.com/site/Scosche+-+2-Channel+Adjustable+Line-Out+Converter+-+Clear/9066093.p?id=1218015169429&skuId=9066093&st=Scosche

why not get a headunit that has rca's... that seems cheaper and easier in the long run rather than buying stuff to fix crap over and over. its already happened twice, what do you think will keep happening.