Tks for the kind words.

The LOC's inside an amp are usually not the same design as the LOC's you can buy from specialty companies like Soundgate. Since it's not often used, the amp manufacturer usually doesn't put a whole lot into the board for that function - usually a few resistors - best suited for low-power applications like the speaker wires that come off of the back fo a radio, when there's not an external OEM amp present..

Many external LOC's use transformers to isolate the outputs of the OEM amp from the inputs of the aftermarket amp. While the effects of transformers in this application can be debated from a sound quality perspective, when dealing with higher-power amplifier outputs, they are the best way to go.

Additionally, if you are doing what we did and summing multiple channels together to eliminate the OEM amp's internal crossover points occuring at frequencies we didn't want to have separate, you need transformer islolation in order to be able to "sum" these back together on the other side of your LOC output. The LOC in the amp can't accomodate this sort of application - but it's needed in many BMW systems (and others as well).

Often, the best use of the LOC inside an amp is to add a sub to an existing system - when engine noise can't be heard.

Now, SOME amps have such a wide input voltage variation (JL, for one, if you flip the switch) that you can run speaker wires straight in. THis is nice - IF the speaker wire is carrying a signal you want to amplify.