New KT150 tubes?

The KT-120s sound fine but the internals of 1 were clearly not given a good visual QC... the posts (anode?) for the vertical glowing conductors are shorter above the top mica plate than the other 3 and guaranteed that when circuit protection cuts in, that's the culprit tube.

I do have one dissimilar 120, and since it works fine I ignore that although it did bug me...but I get it. I suppose the good news is the fact that anybody makes tubes at all since it really seems to be a fiddly hands on thing. I watched an entire old film about the Blackburn Mullard factory (somebody here posted the link)...amazing.

Has anyone contacted ARC about using KT150s in their amps?

Also, Naggots, which manufacturer suggests 7000 hours for the KT120?

Yes, The KT 150's have arrived and they are spectacular. I am originally an EL-34 guy who was addicted to the midrange but also played with SED winged C 6550's for their better extension and somewhat more openness, speed and clarity across the board. I've also run EH KT-88's, so this is the extent of the brand and models my Cary Sa 280 V12R's and my CJ Premier 12's were fed. I have used both amps individually and both amps together bi-amping my Apogee Duetta Sigs (Rebuilt by True Sound Works). A lot of fun. I used an active dedicated electronic crossover in the final combination before I switched out both amps but at the time it was CJ's handling the woofers and the Cary handling the mid/tweeter...Punch/dynamics, extension, serious imaging and space and glorious vocals.
Fast forward to my new TRL mono blocs and the arrival of the KT 120's. Very punchy, good extension, nice air and a mid that wasn't quite the same as an EL-34 but surprisingly on the warm-er side of things....I had heard it would have the extension of a high powered KT-88 along with mids approaching a 34...Overall it wasn't too far off but I felt the mids were perhaps just a little too "warm and fuzzy" for my application... You had to really be discerning because the overall sound of the tube was very nice, but for my system it came pretty close but didn't quite replace the 34/6550 combo I had hoped.
Don't get me wrong...I was pretty much "Done" as far as tubes...they were reliable, seemingly robust, and did a very satisfying job, albeit with the described points...
When someone first mentioned KT 150's my first instinct was to say 'Why do we need that??" Will it be an improvement? Really? And is there really a market for even more power? (the 120's were "plenty" although the expression about having more power is usually nice...).
Fast forward again and I managed to get myself 2 matched quads of brand new 150's (My amp manufacturer (TRL) not only said my amps could handle them but actually encouraged me to try them as he was having great results and really liked the tube). So I replaced the 120's with the 150's and was very pleasantly surprised by how much more they added to the mix...Essentially all the benefits of the 120's plus a midrange that rivals my beloved EL-34's AND gets me the top to bottom extension of an 88 or the 120's in spades. Even more dynamic than you thought you'd ever want, as I said: "great mids"...and sweet highs [though I haven't completely explored to full top and bottom yet as my amps had been recently rebuilt and are still breaking in]. Very very promising though..I think they're a real winner.
Try them.

Xri16 just heard the KT-150 the other day on a Octave RE-290, compared to the KT-120 is like comparing a Rolls Royce to a Toyota. Surpasses the KT-120 in every way. A more extended bandwidth with a blacker background, bigger and deeper soundstage, a much fuller sound with a lot less grain. Once you hear this tube, all the other tubes just simply became obsolete, a perfect match with the current Genelex Gold Lion input tubes, in this case the 12AU-7's. Can't wait for them to issue a Gold Lion version of this tube.