Tell us about your KT150 experience

Curious to hear how they compare to KT120s.

The amps that I have heard that utilize KT120's have not been in my system, so very hard to say...I would be interested in this answer as well from someone who has had the two types in their system.

I have a PrimaLuna HP Integrated.  I've used EL34, KT120, KT150, and now Tung-Sol 7581A.  This is what I found:

The EL34 has a sweet, sweet sound.  Midrange is awesome, and they work very well for vocals and more.  But, they aren't as powerful in the extremes.

The KT120 adds more power, and wider range.  But, what I noticed after having them in the system for a while is that they have a certain "grainy" sound, particularly in mid range.  So, I could hear it around vocals.  For example, listening to Dire Straits, Mark's voice sounded kind of "fuzzy".

KT150 is a nice combination of both.  It has the power, wide bandwidth, and a nice midrange without the glare.  I like them a lot.  The problem is that they are expensive.  They definitely make the amp shine, and I thought they would be my forever tubes.

Then I found the TungSol tubes.  They are like $30 each, so the price is right.  When I plugged them in, they also have a really sweet midrange, seems have similar overall power and midrange.  Also, they have a cool blue glow at the bottom of the tube that you can see when the lights are low.  Looks cool.  I have had them in for about two months, and have not yet switched back to the KT150s.  I will do that soon, knowing I can compare two sets of well broken-in tubes.  I think it will be very close to a wash between the two.  But, given the cost, if I replace, the KT150's cost triple and I'm not sure it's worth the extra cost.

If you are looking at KT120 to KT150, I would say you'll be happy.  But, I'd suggest you try the TungSol 7581A first.  It's a lot less sunk money if you don't like them.  It says a lot to me that I haven't been tempted to go back to the KT150s so far.