Significant sonic changes moving from KT120's to KT150's?

Yep, a bad power tube can be hell.

 

Brian, did you ever spend much time with the stock EL-34s? Or maybe you upgraded those out-of-the-box? I've kept those in my Dialogue and have loved them, but I am itching to see what else is out there.

 

I have often read the KT120's referred to as like EL34's on steroids.

 

I might say a stronger KT77. Maybe more neutral than the EL34s, but it all depends on what they are plugged into, as we know. In terms of quantification, I have heard it expressed that the KT120s deliver approx. 17% more power. If you look at measurements, they do not look that great, but they are a good all-around tube and they are in current production. I’m happy.

 

Would someone who prefers the sound of EL34's over KT88's, be happy with KT120's or KT150's?

 

Also, the other thing is that not all EL34's sound the same, I have a preference for the Winged C's now no longer produced

They have a very even handed way to deal with the whole frequency response, Nothing over or under done...just right in my view.....a very linear tube when triode strapped also....El34's that is.

 

Smooth sounding brass with brand new output tubes? Whoa. I am envious. How do you guys get it and I don't?

 

Possibly. My long run with the EL34s was a good one, but I was often trying to bring the mids forward a bit. This is with a semi-omnidirectional speaker. The KT150s, from reports, are the superior tube. KT120s are solid top to bottom, but may lack some of the ability to throw sound around and ultimately seduce. What you get in the trade is more low end authority and a very nice, silky extended top end. That's based on my very subjective experience and my reading of other peoples opinions.

 

My PrimaLuna came with the 120's, so no experience with the El-34's.

The extra umph from the KT-150's has definitely improved the triode mode option on my PrimaLuna. Since adding the KT-150's, I find myself listening in triode mode A LOT.

I think it's because (a) I seem to be able to listen at louder levels than before without things starting to fall apart. Triode seems to work best at higher volumes for me. (b) my new analog front-end hasn't been fully dialed in and is still breaking in, so it's a bit bright at times. Triode seems to smooth the highs a bit.

 

I added a pair of KT150's to my Rogue Audio M180 and the sound was many times better than the KT120's. It was less harsh, better/tighter bass and a beautiful midrange. The highs are nice as well not bright and the correct level with the bass and mid range. I'm running it in triode mode since it sounds better to me in this mode but is sounds fine in tetrode mode as well it's just the highs are not as defined and smooth. I would never go back to the KT120's!!

 

Ken Stevens of Convergent Audio Technology tried KT150's in his amps. He showed me some that he had in the shop while I was visiting. He said the KT150's had a higher failure rate, which was unacceptable. He told me about some measurements, that I have no idea what he was talking about, but I think he meant they measured pretty close to each other. Ken didn't think there was a sonic improvement in his amp design. So, it may be a design difference since Ken went all in with the KT120's.

Of course KT150's have been in production for some time now and I wouldn't be surprised that they are pretty reliable at this time.
I could try some KT150's but I am very happy with the KT120's, which sound better than the Winged C 6550's that I really liked.