Questions on KT150 tubes

This is what to expect to hear in an EL34, KT88, KT120, KT150 tube:  EL34 -- warm lush sweet mids.  Nice bass and highs but without the bass slam OR impact that may be desirable for rock and classical music or even a nice jazz drum solo.  Minimal, but reasonable bass and high extension.  Fine imaging but not jaw-dropping.  KT88 -- much more bass slam and bass extension.  This also holds true for the highs.  Greater sparkle than the EL34.  Mids are dryer than the EL34 (sweet, like candy) but female vocals are very natural and in-your-room present.  Imaging is more precise and detailed than the EL34.  The KT88 offers a bit more power, too.  KT120 -- a somewhat digital sound.  When this tube was first introduced many tubies scooped it up for the increased power.  Fine.  But this digital texture pushed many tube rollers back to the EL34 (much more musical, warm, lush mids,etc.) or even back to the KT88 depending on bass impact preference.  But now that the KT150 has appeared.  The KT150 offers more power and a longer life than any of the above mentioned tubes (about 10,000 hours in a cool running Primaluna amp).  The KT 150 has killer bass slam and extension.  The highs have a clear and very present sparkle (love the clocks in DSOTM).  Imaging and sound stage are alive, full, detailed, and 3D.  Jazz, classical, and rock listeners will really love this tube.  Mids do not have the syrup that the EL34 has (a deal breaker for some listeners) but IMO they are natural, forward, and glorious.  Truly, the KT150 is the tube of choice for those who want excellent bass power and extension, crisp highs, detailed mids (not sweet), excellent imaging, and long tube life.

Excellent post and very informative.  I totally agree with your assessment on the KT 120.  I find them too digital sounding also.  

If anyone is interested I may sell my matched quad of 120's from Kevin Deal. At the most they probably have no more than 40-50 hrs. 

I don't recall breaking in the 150s for any particular time period since I replaced a set of 120s that were on their last legs…thus an instant improvement. Also, I can only assume that since all amp designs are somewhat different, so are the way they utilize the tone potential of various tube types…I bought my 150s for under 300 bucks a set (matched, dusted off, weighed, counseled, told to not be afraid of crazy Americans, allowed to say goodbye to tubes who were still in that lonely Russian factory) and if ARC supplies some brand specific mojo I'm not surprised they'd charge you more for these things…another reason to buy a Jolida!