What did you experience when tube rolling in a Carver Crimson 275?

Be careful there OP, Brand is one thing swapping types is something else. It will say right in you manual what will fit.. KT90 120 150.

As far as signal valves, 12AT7, 12AX7 are the VERY popular.

I always wondered what the new Crimson was like.. Cool running from what I hear and super long valve life.. The weight isn't through the roof either..

Carver makes some Lookers for sure..  I met that guy WAY back... He was hand winding a transformer on a machine at one end of our class room.  Looked like he was a snake wrestler.. LOL

I've rolled both Genalex Gold Lion KT-88 and currently have Psvane KT-88TII in the amp with ear pleasing results for both. They tend to run hotter than the KT-120's but not like a furnace hot. I adjust the bias control to +/-80mA and both brands sound pretty darn sweet. Also have Genalex in the front sockets. The manual suggests several alternative output tubes but not KT-150. I'd probably inquire with them prior to making that swap. 

@oldhvymec,  yes indeed I wouldn't just pop in something that doesn't fit the specs and tube pinouts.  Further, KT150s may not be recommended.  I heard some say Frank Malitz told them they could be used with the caveat that the amp was voiced to the KT120s.   

@motoraway,  Thank you for that information.  I'll try some KT77s/KT88s next.  

I'm particularly curious to hear if people think swapping the 12 volt tubes have less significance in this amp as opposed to other amps. 

Status Update--

I have rolled quite a few signal/input tubes.  So I finally got around to putting in different power tubes. 

I am running Tung Sol 7581A (reissues, of course).  I think this tube is basically an upgraded 6L6GC tube.  It does have some (slightly) more headroom as its plate dissipation is rated up to 35W.

I had to let them warm up for 10 minutes before they would bias properly.  They did and stayed there perfectly--haven't moved. 

The midrange is more forward and pronounced with a touch more sweetness than the KT120s.  Bass is tighter and more defined, but it's not as prominent.  

Highs have similar air as the 120s, yet the sound a touch crisper/shinier--not brighter though.  

Very fun endeavor.