Originally Posted by Carisma Audio
Advise from someone that has installed for 20 years don't take shortcuts you will end up with issues!!! If you do not have line level in use a line level convertor so your system works properly.
Good advice here.. and yes I know this thread is old but some of the information posted here is incorrect.
First HK does in fact use isolated grounds on their headunits so they are NOT common and this method of soldering RCA jacks directly to speaker leads should not be used. There is a reason for converting speaker leads to RCA jacks using an appropriate adapter and it usually boils down to ground loops and input voltages for amps. Yes some amps can handle high level inputs, but those that do not have high level inputs, CANNOT. You tie high level inputs into an amp that only has RCA jacks and I can almost guarantee a short life span of your amp. Ground loops, well this has been the evil witch in car audio since way before I started doing it in the early 80s. Ground issues can be a biatch to troubleshoot if you've got those issues so why do something like this and make your troubleshooting steps that much more complicated.