Adding RCA outputs from Nav for Sub Amp

[2carcam2]

HI:Just wondering if anyone has tried to add their own rca amp outputs to the factory navigation head unit.I would prefer not to use the speaker to rca line level box,as I've heard that these sometimes can generate system noise.
I have checked the schematic electrical drawings of the head unit to the amp and found that the signal wires are connector F9 and pins 10ground,19L-,9L+,18R-,8R+. What is not said is which are the front and rear? All I know is Left and Right.
Buy the way I have also custom built a sub box for the rear that sits right above the traction battery pack.
What a nightmare that was .I had to modify the air inlet fan cooling tube to a different side of the top mounted air inlet that sits on the back deck and left the original air input as a bass port to allow the bass to get from the trunk to the passenger cabin.
Not finished the project yet,but should get done soon.
Will try to post some completed pics when it's completed.
Thanks
OH almost forgot it's an 08 TCH

[ukrkoz]

well, not sure what you call speaker to sub RCA level box, but I reckon, I have exactly that for well over a year now. it's a small box with 2 level controls spliced directly into the driver side rear speaker.
WORKS LIKE A CHAMP.

[jordan_lin]

the output directly from the deck itself is a fixed level left and right channel output. the signal is not dependent to the volume control at all. the job of the jbl deck is only to supply the music signal, then all the volume, fader, and balancing portion is actually done by the amplifier and is communicated digitally. so your only choice is to use the speaker level and convert to rca. from what you say about the module generating noise is very unlikely unless it's defective. but you are right, it brings more distortion to the bass. there are 2 solution you can go about, one is using amplifiers that has speaker level input and hook it up directly so no need to use RCA. the second is get a better speaker level to rca convertor that cost around $100. many active crossover or processor has this kind of capability.

[ukrkoz]

this is what I have: