I figure Gonk can answer this one: When playing vinyl On "stereo" I get the stereo signal; I know that when I play phono on "bypass" I'm getting the straight thru signal; but what, if anything, is happening when I select "upsample" while playing my favorite Moby Grape album?

If you select "Upsample" with a stereo analog source, the source is converted to digital, upsampled, processed (for bass management only, basically, as there is no surround processing), converted to analog, and output. It's still stereo all the way along.

Thanks Gonk, you da man.....

This has always confused me. What is the difference between an analog source processed as STEREO vs. UPSAMPLE. The confusing part is that the A/D converter in the 990 already samples the signal at 24 bits and 192kHz when it converts to digital, even in STEREO. How can you upsample to 192kHz if it's already at 192kHz?

This is different from a CD which is digital and sampled at only 44 kHz. It can be upsampled to 192kHz before being converted to analog. Most better CD/DVD players nowadays do this. I can imagine that even a digital signal from a DVD-A at 96kHZ could be upsampled to 192kHz with some theoretical benefit.

I'm just guessing here (haven't ever really thought much about it or looked at it too deeply), but if this page is correct the ADC is 24/96, not 24/192 - in which case you could still upsample from 96 to 192 after the A/D conversion.