Proper use of Line Out Converters

As mentioned in an earlier post, I did a three amp install in a Cadiallac Concourse Deville; two mono and one four channel, all Alpine. I used one line out converter on the two speaker leads in the rear deck which I believe are factory amplified. I also removed the rear speakers. This is a two channel LOC that I split into four with Y adapters for input into the four channel. I then split the pass thru on the four channel to feed signal to the two mono amps. Everything worked fine for a month or so, then I did a follow up on the system. One of the channels on the LOC wasn't working so I popped it open. Some of the wires and the circuit board was melted inside. So my question to this forum is, how to properly use Line Out Converters? Did I use a cheap quality converter? Are they not compatable with factory amped systems? Were the gains on the converter set too high? Or can you not use one converter for more than one amplifier. I consider myself to be a good installer, but I've never read anything on what "Not" to do with LOCs; not even in my trusty 400 page MECP advanced study guide. Any help would be greatly appreciated as I don't want anyone else to make this mistake again."My Lifestyle Determines My Deathstyle"

Yeah it isn't something real mysterious. It is either failure of components, or that specific loc wasn't made to handle the ammount of wattage you were putting into it. Most good locs have some sort of switch that will let you set weather the input is from an amped system or a headunit. fiberglass reminds me of peanut brittle... but fiberglass tastes better!