What's causing hiss??

I don't know all of the usual diagnostic steps you may want to take. I do know as a tubophile, that tubes can be the source of a hiss. If you can swap out the tube/s in the preamp section you may find your answer very quickly.
You should also be aware that tube equipment is inherently noisier, not that all tube systems are noisy. What I am trying to say is that if you are very sensitive to background noises some tube systems will never be quiet enough for you.

What Mechans said. Incidentally and apropos of nothing, it's this constant dance of second-guessing and general fussery that sent me - with much wailing and gnashing of teeth - back into the comforting, predictable camp of solid state. Say whatever you like about the sound, tubes are unquestionably higher-maintenance, less predictable, and more like living little bits in their own right, in all of the good and bad connotations that might evoke. Just part of their care and feeding to grow accustomed to, although once you get the right ones in a preamp section, you can usually forget about them for a couple years. Unless, of course, you can't.... ;)

Is the hiss audible at your listening position or just when you put your ear up to the speakers? Assuming the latter, this is not uncommon at all and much depends on the efficiency of your speakers and/or the noise level of your tubes. Get some new tubes tested for noise, i.e. they are graded as 'low noise'. This will solve most of these issues unless you have very efficient speakers that are revealing the noise threshold level of your electronics.

Yes the hiss is the same in both channels and same volume (can hear it from listening position=unacceptable) with any of my 5 inputs selected at volume=0.

I tried an experiment this morning. I sent the tube pre section out to my el cheapo but zero noise t-amp and the hiss went down considerably. T-amp is 15 watts, integrated is 150 watts, speakers are a super efficient 104 db Klipsch LaScala.

Maybe the answer is find a low noise, low gain tube pre amp to pair with my T amp.