Audiophile pre-amps with home theater pass through

Can someone elaborate on what the unity gain feature of the BAT pre's is/does and how it relates to integrating a home theatre system into a two channel hi end system?

thanks

To answer Scotty above, on my BAT VK-30SE you can set the relative level of any of the inputs wherever you want it and then assign that input as a "Fixed" input. No matter what you do with the BAT volume control the level of the fixed input doesn't change. Rather, volume is controled via your Pre-pro of choice.

In my setup that means I set all my home theater levels at my Accurus ACT 3. Center, surrounds and LFE go directly out to amps feeding speakers for those locations. L & R front channels are fed from the ACT 3 to my BAT, and it in turn feeds the 2 channel amps.

Voila! Home theater through the 2 channel setup, all the while maintaining the integrity of the 2 channel setup for serious music.

Sonic Frontiers Line 1 (~$1000 used) and Line 2 (~$1400 used). Both preamps are tube-based.

A little more money but ML380S is the best