I've read a numerous amount of posts but users are bypassing the stock radio when they bypass the factory amp. I'd like to keep that portion factory if I can.

1. Like to bypass the factory ml amp.
2. Install a 4 and 1 channel amp(s)
​​3. Install 4 new speakers and sub. Disconnect the rest.
4. Keep the stock radio/CD player
5. Install the from unit which allows mirroring ones phone

questions:
What harnesses does one need to keep or purchase for the AC controls to still work on the center control panel?

What other gotchas are there?

Was planning on repurposing the factory wiring routed to the speakers as much as possible. Tie the factory radio input to the OEM amp into a loc(s) then tie that into a new amp, then to the existing oem amp out wiring, then to new speakers.
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You've found numerous posts about bypassing the ML amp? I haven't seen one. Please post a link to those.

We are talking about an LS430 with ML stereo right?

 

It's my understanding that there is no easy way to obtain a line-level output from the factory radio, you have to use line-out converters after the ML amp. That won't provide a nice, flat signal to work with. Also, the ML amp is not very reliable, so once that goes then you won't be able to get a signal from the radio.

The long and short of it is if you plan to upgrade audio and want a nice, clean setup the best solution would be to start with a base model without Nav, and then install a Metra or Beatsonic double-din adapter.

 

check out this video, it's possible and you need to know how to re-wired the aftermarket harness to match up with factory connection.

 

At 26 seconds the installer states that this particular vehicle already has an aftermarket head unit. So all he is doing is using the factory wiring harness to connect an aftermarket amp to the factory speakers. The aftermarket amp is getting signal from RCA's. If you take a look at my thread I show you how to do that as well.

https://www.clublexus.com/forums/ls-...rs-needed.html

The OP's question is how to utilize the factory radio controls with an aftermarket amp. Not the same thing.