Been meaning to update this thread with some Lexus Mark Levinson (ML) upgrade information...Shortly after the 2008 model year, all of the ML units became full 5.1-channel units...
I have the ML in my '09 ES, so I can fill in a few blanks for you. I noticed that there was no discrete 5.1 from my DVD-As, and spent the next half-year on an odyssey with my Lexus dealer, Lexus Customer "Satisfaction", Lexus Corporate and Harman, to determine what, if anything, could be done about it.
The defining moment came when I managed to get a Harman engineer on the phone, who was kind enough to tell me what was up with the ML. The head unit is capable of reading a DVD-A, but the input stage of the multichannel amp/processor cannot handle the throughput, so it downmixes uncompressed 5.1 to stereo! This occurred as these systems are designed to meet a price-point dictated by the client, in this case, Lexus. As it happens, continual incremental design improvements are employed as the bang-for-the-buck ratio of technology improves, and 2010 saw the first generation of ML systems that were capable of discrete 5.1 reproduction. Missed it by that much!
I've had the opportunity to hear a couple 2010 and 2011 MLs in action, and while they are 5.1 capable, the overall SQ apparently is surprisingly dependent on which model line they're in, the thousands of man-hours of fine-tuning the system touted in Lexus ad copy notwithstanding!
On a personal note, a happy ending in two parts with regard to my own ML: One, since the ML can play DTS 5.1 discretely, I converted my DVD-As to DTS-CDs, which avoids any playback difficulties with the notorious nanny-car DVD screen lockout, and two, a concise letter of complaint directed to the appropriate vice-president in the Lexus division of Toyota Motor Sales USA ultimately got me a refund in the amount of the MSRP of the ML system.
Bob
