KT150 to KT120..or KT120 to KT150

1/8/2022:

KT150 > KT120s. Re-testing and giving it a lot more time this go-around with two mono amplifiers specifically designed to run KT120s and KT150s. Big transformers, higher plate voltage, 40-45ma per tube bias.

Picked up a quad of Tung Sol KT120s a week ago. Giving it another try after locating and reading back through threads I’d not seen before on the CJ Owners Forum and DIY builders, noting several members favoring KT120s over KT150s and KT88s. I kept seeing these comments, and realized it was time for a complete do-over.

Update;

At 48hrs burn-in on the KT120s, here is what I’m noticing in comparison to KT150s. After more time and paying close attention, I’m observing similar traits as others.

The KT120s vs. KT150s, are:

• A little more rolled off on top frequency.
• Less low-low-end bass extension.
• More musical midrange, tone, texture.
• Not as clear and extended, but still nice.
• Engaging. Enjoyable, a bit more vintage tone.
• Closer to KT88 sound than KT150s.

Adding to the thread, hope it helps others. I’ve come to appreciate the KT120s a lot more than I did the first time around.  They are a nice [go-between] alternative to KT88s or the more clear and linear sounding KT150s.

In my listening, I feel kt150 is much hifi than  kt88 and  kt120.

I have kt150 right in my audio research ref 75se,and  I definitely will change back to kt120 when these kt150 retire later.

There are lots of things in the music,which you prefer? Will decide your choice with the tube.

I listen vocal Jazz, voice really matter to me, the music  meat is important to me,large 3D body is not so important to me.

It is my choice.

So in total, you definitely can not say which one is better, but obviously there are two league, kt150. Or kt88,kt120.

@decooney  +1 very good description between kt120 and kt150.

I agree with others that, in part, it depends on the amplifier design.

The just released Zesto Audio Bia 200 Select has a selector switch with three positions; KT88, KT120, KT150 or KT170 with power output 60, 80 or 100W depending on tube and selector position. These amps ship with KT150 tubes presumably because that's what the designer prefers. It's nice to have the option of optimizing the amplifier for different tube types.

I have one on the way and look forward to playing about with all four tube types within the three operational options. My Fyne F703 speakers are relatively efficient so 60, 80 or 100W will be more than sufficient power.

@runwell So in total, you definitely can not say which one is better, but obviously there are two league, kt150. Or kt88,kt120.

runwell, I agree with your comments and description. The plan is to rotate the KT150s back in every once in a while. They are an amazing wide range tube with added depth, clarity, sound stage. Definitely in a class of their own, yes, agree.

However, the KT120s are a "throwback" to older familiar tube sounds I use to enjoy and expect from all of my former tube amplifiers with el34s, kt88. A nice tradeoff too.

I understand >> a lot better now << what some were reporting about why they liked or preferred KT120s over KT150s. There are different reasons I like and appreciate both - particularly when used with purpose built amplifiers designed to run them.