The Luxman L-509x is biased for 6 watts Class A before going AB to rated output.
Depending on speaker pairing, most/all listening can be in Class A.
Luxman 550AXii and 509X
I had the good situation of being able to borrow the demo units of the Luxman 550AXii and the 509X from the dealer and listen to them side by side at home. I went with purchasing the 550AXii new. Just wanted to share my observations..
1) Build quality is nice for both. The 509X looks more modern with the beveled edges and super nice solid top.
2) The VU meter on the 550AXii has gentle smooth movement, on the 509X it feels like it's in a rush
3) Sound quality, for me the 550AXii is the clear winner, it is more authoritative in spite of lower wattage at 40W. The 509X feels a little sterile and lacking bass, although it is very clear. Some might prefer that..
4) Went through multiple genre of music, and the 550AXii shines in all that I listened. The 509X fell short on deep house, and I had to hit the loudness button for classical music.