McIntosh MC275

I own the mc275 vi version and love it.  Mine has the LED tube indicators, but I don’t believe yours does.  Ron Cornelius at Mcintosh told me that on average the 275 tubes last between 5,000-10,000 hours...so if you like the sounds of the tubes you have, they should still have lots of life.  

As as far as tubes, I’ve swapped out a few tubes.  I really like the golden lion kt-88, they seem to have more body and bass.  I tried the newer tung-sols in the 12ax7 spots, but didn’t care for them.  They sound thin.  My current setup (that I like the best so far), 1 Golden lion 12ax7 inverter spot, with 2 RCA 12ax7 followed by rca blackplates 12at7.  However, everyone’s ears and stereo is different. Good luck!

Tubes are not light bulbs!   I had a MC275 years ago with new tubes.  I could listen in a dark room and all I saw was a glow.  A nice warm glow. 

I don't know... I'm pretty sure they're just glorified light bulbs. If you take a light bulb and you put an anode in it you just made a diode. And if you put a control screen between the filament and the anode you just made a triode. 

I'm a proud owner of a Mc 275 mk3,my tubes are not bright or lite up like other tube amps I've owned so I think theres a pattern here,however  never an issue and love the sound,of course my kt 88s are Black Treasures so you can't see them well any how,but the 12 ax7 s don't burn bright either, wouldn't be concerned! 

If you really want to see the tubes glow, you can turn up your preamp as loud as it can go, and the power tubes do tend to glow a little brighter.

Seriously though, there are many amps and preamp out there that the tubes barely glow.  I have a Berning TF-10 that you can barely tell the tubes are on.  Tube brightness is no indication if they are "good" or not.  

2112oracle:  Have you tried any other KT-88's?  I was curious about the black treasures, but the cost at the time was a little steep for me.