Line level converter reduced sound...

I've got a 2003 Silverado with the factory RDS HU where I've tapped into the Rear L/R speaker lines for the Hi/Lo adapter to run an amp for a sub.  I've left the adapter gains at default (middle of the full range for the pot), and now the sound level of the rear speakers has diminished significantly. I've had to fade to the rears about half way to get the same amount of sound I had prior to installing the hi/lo.

I have nothing currently connected to the RCA's from the hi/lo (waiting for custom box), and I followed the following wiring diagram to tap the rear speakers.  Why would simply tapping into those lines cause any problems with what the rear speakers would 'see'.. voltage or resistance wise? Note that I have a 2003, and the diagram is for the 2000, but all spkr. colors matched the same. Have I got a phase issue, hi/lo gain adjustment, should I connect the isolation ground on the hi/lo..???  Any other suggestions?

2000 Chevrolet Silverado Stereo Information

I would think if you wired up the converter in parallel with the factory speaker wiring, then the head unit or factory amp would get fried before the volume would decrease.  The only time the power (and thus volume) to the speakers is reduced is if you connected everything in series.  in series wiring the impedence doubles and there's more opposition to current flow-->less volume for each speaker.

The weird thing though in your situation is that you said it's still not really even hooked up to anything, in terms of the output signal.  If you have somewhat easy access to the converter, I'd try listening to the system with it installed, then with the system still turned on, remove the converter and see if you notice the sound increase.  If there's no audible increase then I'd say your problem lies elsewhere.  If right away you notice a big increase in the sound, I'd say something is either wrong with how you've got it hooked up, or the converter itself is defective.

If you can get your hands on a multimeter and can get to the factory amplifier or head unit, test the resistance of the rear speaker leads.  If it says something like 8 ohms then the line out converter is somehow hooked up to the factory wiring in series as mentioned before.  If it says 4 or 2 ohms then the problem is something else.

OK, here's the deal....  all rear speaker wires are T-tapped to the LOC. I'm installing as directed given the "floating ground" configuration, as opposed to the common ground (where the LOC says connect L & R (-) together to a chassis ground or HU ground point.).  BTW it's a PIE ( EIS-LOC-AF or AM) Float or Common ground, 1-6V p-p input, 1-25ohm, 30W max input/chan.

Left Rear (+) Brown            -----  L(+) Wht          ---|               |

Checking the rear speakers with a battery proved that the stated HU speaker wiring was correct in its polarity, and BTW.. the rears had 8ohms printed on them, so I'm not sure if your test would be valid, unless the LOC is 8ohm parallel with the existing speakers, that would then give me 4 ohm from the HU's perspective, but correct me if I'm wrong, but the LOC shouldn't put any additional resistance on the line, should it?  I haven't had a chance to run audio tests with & without the LOC, but I will soon.  I have since connected the amp & sub and noticed I need to do some tweaking on the LOC output pots due to them overdriving the signal into the amp and subsequently making the sub sound like crap. I'll post some results and in the meantime try any other suggestions you might have. Thanks!