Post by
maxnix »
https://forums.nicoclub.com/maxnix-u127.html
Mon Oct 13, 2008 1:58 pm
Well, as I understand it, the adapter harness attempts to match the resistance of the output of the head amp to the expected nominal resistance of the inputs of the Bose amps, all the while maintaining some kind of equalization. Remember, nominal resistance of course varies across frequency, hence the equalization curve matching concern. Some harnesses seem to work better than others judging by anecdotal comments.
I don't quite understand your set up, but if you have after market amps with after market wiring and after market speakers, than going form the preamp out on your head unit should let everything work as well as it can.