Hello there, I was reading that the head unit down samples any music content to 44.1khz/16/24 bit.

I have a hard time understanding how you have a high end music system yet don't allow playback of high resolution files?

Lincoln sync 3/4 Revel and Genesis lexicon all allow native music playback up to 192khz 24bit.

Was disappointed when I read what Lexus does in the manual. It's similar to what Volvo does with the Google OS limiting to CD quality.

Pre Google OS Volvo's would play hi rez content.

That isn't quite right per the 2019 - 2022 Navigation and Multimedia System Owner's Manual:

Starting with the 2023 model year that has changed to:

There's a big difference between what a system accepts as input audio file formats and what the system does with super high resolution formats after reading in the input file.

The Revel, lexicon, and Mark Levinson systems are all Harman International Industries product designs. While I couldn't readily find any detailed input audio file format specs for Revel, what I could find for lexicon implies it does the same sort of down sampling as the ES Mark Levinson system does.

Taken from the 2019-G80-MultiMedia-System-Manual:
Notice all the "to 48 kHz"? That implies that while you may input files with higher sampling frequencies, the system will only process the audio input at a maximum of 48 kHz to output analog audio to the speaker system. No different that what's occurring in the Lexus ES audio system with high sampling frequency input audio files.

If you have references to more specific, detailed specifications on the supported input audio file formats and how they're processed by the system after input for the Lincoln sync 3/4 Revel and Genesis lexicon systems please provide them.

Thinking ML is high end is the misconception. I understand this is up for debate, but from my experience anyone that claims they can hear the difference between 16/44 cd quality and 24/192 in a moving automobile with a near 60dB noise floor (road/tire/wind and engine noise etc) is full of, bias. Even if the vehicle is stopped and playing music in a quiet environment, I very much doubt the speakers in these cars will resolve those extra details, not to mention the uneven frequency response, decay and distortion caused by the sub-optimal positioning and enclosures of car speakers compared to say listening with good headphones or in a studio room. I think Hi-Res is completely moot in cars, playing High-Res would be like putting in race fuel and expecting better performance when it's not capable/designed for it.

Sorry to go off subject.... Does the ML have HD radio?

Yes, for US (and I think Canada also) sold vehicles. (Other markets use different digital radio broadcasting standards.)

For the 2019 to 2022 model years, see the "Using HD RadioTM technology" section in the "4-2. Radio operation" subchapter of the Lexus _____ Navigation and Multimedia System Owner's Manual (page 123/124/125 depending upon model year version).

Starting with the 2023 model year manual version, the "Using HD RadioTM technology" section has been relocated to the "9-1. Appendix" subchapter on page 245.

While I agree with the idea that a person may not hear that specific difference in audio encoding quality, the noise floor in the ES is crazy low. If there's a (sub 100k) car where you can hear the difference, that's the one.