Greg, the fastest way to answer that question would be to call McIntosh. While you're at it, order a service manual/schematic -- that's what I did.
You can also find out by 'naming' the phono input something else (on the menu screen) if you do that, the phono tubes won't light up when you turn the amp on -- at least that's the way their preamps work ;-) (It's a way of saving tubes and reducing heat if you don't have a turntable.)
You can also find out by 'naming' the phono input something else (on the menu screen) if you do that, the phono tubes won't light up when you turn the amp on -- at least that's the way their preamps work ;-) (It's a way of saving tubes and reducing heat if you don't have a turntable.)