There seems to be 2 groups of thought on keeping the stock head unit....

Group one says you need a line out converter like Audiolinks PD4 just after the head unit because the leads are speaker level and then you canrun RCAs to your new amp. The PD4 has a ground loop isolator built in and it has adjustable features that make the system sound great with no noise, hum or hiss.

Group two says the leads coming out of the head unit are pre outs but just not RCA connecors so if you solder on some RCA plugs to these wires you can then plug these into a ground loop isolator to remove and interference and then run RCAs to your new amp. They say by not using a LOC the sound is cleaner and there is no noise, hum or hiss.

So which is the answer? The second method is a lot less expensive but the first method gives a lot more control over the signal. WHAT DO I DO?!?!?! This is so confusing!

 

Are you sure that the "line" outputs on the head unit are not already balanced. From the Helms manual (page 22-145), each of the 4-channels f-l, f-r, r-l, r-r have two wires per channel going to the power amp with a separate shield (I just don’t know and it doesn’t say that they are balanced lines; they could just be separate grounds).

Are you sure that the levels going to the "custom" Bose amp in the back (All 8-lines + ground/shield) are not line level???

IMO -- I'd talk to a few of the folks that DeBosed their systems and get in contact with someone who did a few high-end conversions...