what exactly is ht bypass

More likely the way to run it is with sub, center and surrounds from HT pro..this is because of crossover, leval and delay sttings a tube pre wont offer. A HT bypaas is pretty much what it says as it simply will bypass its own volume, balance and even mute to allow total control of system from the surround unit's outgoing signal. I run a non HT bypass tube pre and its easy to do as you just need to know master volume of tube pre so Processor has correct levels all around but I dont use a sub for 2 channel, and thats you major roadblock.....unless you can input 2 signals into sub via multiple jacks on its inputs or via splitters from your pre and pro without any issue its gonna be a hassle.

It is not difficult. All you need is the right preamp.
And I would suggest getting the tube preamp with HT pass thru rather then using your processor. The only preamps (tube) that I owned that had this feature were Dodd Audio and Granite Audio. It is as simple as ABC. In Dodd's case the unite did not even had to be turned on for this feature to work...as long as you turn its input selector to HT bypass input. Very cool, and saves tube live.

With "Home Theater bypass" inputs , you can plug the left and right front speaker feeds from your surround processor into the preamplifier's HT bypass "in". Using your remote control or manually, simply press 'HT bypass' or turn the input selector knob and the preamp goes into its fixed amplifier mode enabling your surround processor to control the volume.

I am looking at doing the same as soon as the money is there. My sights are set on the LS26. One thing I have learned while deciding what to buy is that some manufactures refer to this feature as "unity gain" so keep that in mind when shopping. As Mrjstark stated it allows you to use one amp and speakers for both 2 channel and HT and basically the HT Mode on the stereo pre amp is just a completed circuit between the pre-pro and the amp and when in a source input is selected the pre/pro is completely out of the picture. I just learned about this last year from a factory rep at the RMAF and realized I can have a 2 channel and a ht system on a budget I can afford....eventually.

thanx guys....this seems to be one of those things i really cant wrap my head round for some reason..odd as i have dismanteld..and 'remantled'..lol..my system a hundred times..let me tell u my system..perhaps that will give u guys a better idea here..currently i have a yamaha receiver..connected to a dreadnaught amp..3 channel....so..i have the outs from yammy going to L R C on theta..and surrounds and sub powered by yammy. I want to add a pre tube because i love listening to music. So..the pre has 2 outputs and an 'ht bypass'....one output would be for mains..one for sub...so..if i go mains then from yammy to ht input..then to dead?..center can still go from yammy to dread...ahh..i see..sub wont be powered by yammy..therefore..will not mesh into ht?..am i getting warmer on all this!!..lol..thanx for the anticipated help