Never mind... I found it. It's a 300 microsecond crossfeed delay option that seems to be available on all their amps. I wondered if they tried to simulate the typical frequency-dependent shadowing that occurs, but apparently not. It seems to get mixed reviews on Head-Fi. Many folks who've tried it don't like it or use it, some like it all the time, some try it on every new thing they listen to just in case and many use it only on older recordings with strong panning of mono tracks. I'd be interested to try it out... perhaps I can simulate it in the box with some plug ins...
Cheers,
Otto