should i go with kt150's now or wait a bit??

Dweller is perky huh? Man...Keep the 120s as backup maybe…can't hurt. My trusty 120s wore out after 3 years in the aforementioned (Jedinite…dude has great taste in amps, as does tomtab) 502P, and the 150s had just become less expensive so I got a quad...in they went and after over a year they continue to sound friggin' great and I hope they last as long as the 120s.

I just read a thing in a recent UK mag (HIFI News or something) where the reviewer, who loves (I mean REALLY loves) his Audio Research Ref 75 with KT120s, reviews the new AR GSi75 integrated. He goes nuts because although the new integrated is supposed to be the same power output as his amp from the same damn company, it blows away his Ref 75 in term of power and control over his reference speakers…he's absolutely sure it's the KT150s making the difference although it is a different amp of course…still...Besides, they're shaped like pickles, they're larger, and amp designers are all over these things so what's not to like?

This particular "sucker" waited until my trusty 120 reached the end of their road (3 years of hard pressed tubing), and I would have certainly bought another quad of them except for the fact that 150s had engendered such raves and cost $269 for a no bullshit quad ("factory matched" no "cryo me a river" or Careful Selection price increased ARC style nonsense) from the people who sold me the 120s previously. A 100% reputable Ebay seller with a return policy. They KILL in my modded Jolida…actually they don't kill anything except microphonics supposedly, and when they die I'll get another quad unless New Sensor comes up with something else.

I compared the Tung Sol 6550s (stock with the Jolida 502p) and a set of Sovtek Kt88s to the 120s and the 120s were better sounding, although the other tubes sounded pretty damn good…note the front end tubes were swapped all over the place until I wound up with a Gold Lion (12AX7)/NOS Mullard (gold pin 6201/12AT7) combo that works well…the 150s sounded much better than the 120s but the 120s were on their last legs anyway.

Don't forget the 753 hour break-in period (heh…). I can sympathize regarding sonic attributes of tube swaps as the differences are obviously subjective and often subtle. After all, it's the same amp…I can say that the 150s in my 502 have stayed absolutely static (no sonic degradation I can hear) over thousands of hours, and I rarely adjust the bias (generally only when it "seems" unbalanced, but this likely has more to do with the unstable electricity in my house, and my propensity to fiddle and burn my fingers). I expect thousands of hours more from these tubes as my 120s lasted longer than I expected anyway…we shall see…Also, I wonder why they don't produce a gold pin version of these things.