Land Cruiser Partial Bypass

Today I completed one of my biggest car stereo jobs of the year, and the result far exceeded expectations! My customer brought me a 1998 Toyota Land Cruiser with the premium sound system in it. He wanted a complete upgrade: Apple Car Play stereo, new speakers all around, satellite radio, and backup camera.

Just one catch. According to the various Land Cruiser blogs I consulted, integrating the new stereo to the factory amp was problematic. Due to an oddly designed ground loop, if the new stereo’s line level output was connected to the factory amp’s input wiring, it would generate unacceptable noise levels. The amp had to be bypassed. I suggested, and my customer agreed, to insert Pioneer’s tiny GMD1004 amplifier into the bypass to provide him with the extra volume he craved.

But wait! What about the factory subwoofer? If I bypassed the factory amp, the subwoofer would no longer function. Would my customer have to buy another amp? or do without the low bass? Or was there another solution? It seemed to me there was! And so I set about performing a partial bypass.

It’s commonly believed that all aftermarket stereos have four output channels, but that’s not quite true. Some have six, some eight, some ten! Only four are powered, true, but line level outputs can be used at the same time as speaker level outputs, with no harmful effects. And so I set about utilizing eight of the new stereo’s ten outputs to feed both the factory amp and Pioneer’s tiny GMD1004.
















I connected the line level channels to the amp integration wiring adapter, to feed the factory amplifier.

















I fed the speaker level connections into a pair of 16×4 speaker cables. I routed these cables behind the glove box, under the passenger door sill plate, and then routed alongside the factory amp’s wiring to the Pioneer “tiny amp”, which I installed right behind the factory amp. I tucked it under the carpet after the photo shoot!

















Now for the surgery. I tapped into the factory amp’s power and ground wires to run the Pioneer amp. I always use an inline noise filter with these tiny amps, I find that the amp produces a much cleaner sound as a result. I cut the leads running from the factory amp to the door speakers, and spliced the speaker ends to the tiny amp’s output leads. I left the subwoofer leads connected to the factory amp.













When I fired it all up and made some adjustments to the stereo, the results were amazing!  I turned on the stereo’s high pass filters and set them to 100hz front and rear, and then adjusted the equalizer to reduce the 6khz and 12khz bands by 6db. I tested with Joe Bonamassa’s “Mountain Climbing” and I had to admit, it sounded almost as good as my own car! It was like magic!

My customer came to pick up the vehicle and I gave him a test run with his selection of Tom Petty’s “Free Fallin'”. I thought he was going to burst into tears. “You just made my YEAR!” he exclaimed.

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