If your preamp has a good quality volume control there's really no need for a home theater bypass. @reubent is correct.
Preamp:...Add A Pass-Through For Home Theater
I have a DAC/preamp that I'm using for 2-channel. I'd like to use the front speakers in this setup for my home theater...but there is no designated home theater pass-through in the DAC/preamp. Can I use/designate a pair of RCA inputs from the DAC/preamp and route them to the Left and Right front channel inputs on the processor? I'd really like to not have another separate two front speakers in this setup.