Are Their any Tube Preamp with Home Theater Bypass?

I am looking at this issue as well and found this helpful page listing both integrateds and preamps with HT-bypass:

It is updated but not complete (for instance it is missing Modwright).  I have considered moving my Schiit Freya plus to my AVR system, which does not have HT bypass but does have a passive mode.  Some problems I see with just using unity gain are 1) the fear of switching inputs without lowering volume, and 2) I believe that you cannot utilize an unbalanced input (from an AVR for instance) going to a balanced output to your amps in passive mode.  I could be wrong on this second point.

I have a related question.  If you want to incorporate a single subwoofer into both the HT system and 2 channel system, how do you accomplish that?  Do you simply have to use two different inputs into the sub?

@oldrooney Thanks for the information.  I see that now in the manual about converting single-ended input to balanced output.  But I still don't understand if there is any way to fix the volume of the Freya when you have a singled ended AVR input and balanced outputs to amp.  If you want to have the Freya's volume controlled by a connected AVR (single-ended), you would put the Freya in buffered mode and then do what with the volume.  turn the volume all the way up like they suggest to do in passive mode?  Or do you have to determine where the volume should be for playing the AVR and just put it at that spot every time you switch to AVR?  Or would it not matter where the volume is?  This is where I remain confused.

@oldrooney thanks for that. I feared that is how I would have to do this if I moved the freya to my HT system.