Audio Research LS15 vs LS16 pre... Whats the diff?

I'm seeing used LS15's and LS16's and from the photos, these two AR preamps look nearly identical except for some front panel labeling. I know that both of these are tube preamps. Are any of them (or both of them) hybrid with transistors and tubes in the audio chain?

What is the main difference between the LS15 and LS16 models?
And I quote (or is it plagiarize) from the Audio Research website:

"Chassis size and appearance are almost identical to the previous LS15, with the same complement of balanced / single ended inputs and outputs. The only major operational change is that the "Direct" input path of the LS15 is now a single-ended, unity-gain processor pass-through, a feature also included on the LS25 and RE F2. Incorporation in a home theater while preserving great two-channel sound is easier than ever. Input selections have been relabelled to include CD BAL, Phono, Tuner, Aux SE and Aux BAL.

Two additional mechanical changes deserve mention. Toggle switches are now the bidirectional spring-loaded type used on the more costly LS25. And the microprocessor-controlled volume control is also the same as used on the LS25, with a total of 104 individual steps. Both of these changes add greater control flexibility and a higher-quality operational feel.

Inside the LS16, you will find a new Class A gain circuit using four 6922 twin triodes with our proprietary clear damping rings, plus greater energy storage, the latest Infinicaps and improved power-supply regulation. The result is a sonic presentation that goes way, way beyond the LS15! Highs are better defined with a finer grain structure and less electronic hash, the midrange is more pure and open, while bass control, extension and dynamics are vastly improved from the LS15. Overall, there is much greater musical and tonal coherence from top to bottom, while definition of musical structure is more vivid and natural. This wonderfully balanced preamplifier mates extremely well with every vacuum-tube and solid-state amplifier we've tried.

Once you hear it, you will agree that the LS16 represents a new threshold of value for high-end audio preamplifiers, combining versatile features and improved sonic performance. Because of the many improvements and changes, it is not possible to update an LS15 to the LS16 configuration."
Thanks! I should have looked at their website in the first place. ;-)