Sub Amp has Affinity for L/R Bias

Car: 1999 Lexus SC400 Audio: Nakamichi Second thread posted here in 2 days on the same install. Factory sub amp plays low on After- Nak HU/Pre-Stock Amps intercept from 3.5"mm signal direct (w/o line level, etc) Stock door speaker amps are playing perfect. Hooked up laptop for diagnostic purposes and stronger signal. Sub amp played as normal only when ANY balance between Left and Right channel was enabled on the sound card. Why is this? Bad ground on balanced/unbalanced conversion maybe?

There is only 1 factory sub, where their aren't any direct leads from the HU. I tried to cross the wires, where I wasnt able to recreate the sub playing on the balance adjustment. Instead, it stayed quiet. The signal ground conversion was all done via RCAs, so they are color-coded for correctness. Pretty positive there is a crossed wire. I did how, tie the same exact signal to the front and rear speakers. Left and Right. Could this be causing the cancellation? Or did I tap the Signal Wire at the wrong position?

I looked over your other thread- it seems your factory system is intact, and you're not adding any subwoofers.  If you disconnect your iPod, etc. does the problem go away?  If so, try an fm modulator temporarily and see if the problem still exists.My ex once told me I have a perfect face for radio.

Thanks. No I am not adding any subwoofers. Yes, it works intitally. Will try to reset original wiring the morning. Originally, before attempting the install used a CD Cassette Adapter (instead of FM modulator) to add the Aux input. Work perfectly, beside the expected cassette hiss. I interupted the HU signal ground BEFORE the main shield and other signal tap in the line before reaching the amps. My hypothesis is that if I intercept AFTER the main shield takes its readings for the Amps that I might be in the clear with my issues solved. Any thoughts?

I was able to check all the polarities where it matched up. Secondly, I added the inline PIE ISO isolator to try to assist in the phase correction. Upon closer inspection of the standard 3.5mm input to L/R RCA Output, I noticed that the phase "cloud" eliminated itself and the system sounded clear immediately after removing either the Left channel RCA or Right channel RCA. With either unpluged (Left Channel RCA or Right Channel RCA), both speakers sides (Left and Right) still played regardless of the fact. Can anyone explain this?

anyone know?

I know this very cliche, but it was a grounding issue with the iPOD (Aux) neg. After researching more, I made a seperate solid ground as close to the unit as possible instead of tying into the HU signal ground. Issues resolved. Thx