kt77 vrs kt120 in Rogue M180s

That's a very helpful comparison; thanks. I've been using KT120 in my Apollos for a while, and your description of their strengths closely reflects my own observations in replacing the EH KT90. I've been surprised and pleased at how all Rogue gear showcases the voice of each tube, rather than imposing a voicing of its own.

Running KT120s, I occasionally wish for a touch more air and sparkle up top, without tipping over into brightness or shout-iness. Sounds like the KT77 provides that, but not without compromise in other areas. Someday I'll just have to try them for myself. It would be interesting to see whether I observe bass control issues w/ KT77; my Apollos are already way-overkill running into 96dB/Watt 8 ohm speakers.

Mike

One cannot go wrong w/ those KT 120 tubes!

The kt 77s bettered the kt120s in just two areas, upper end extension, and depth. The kt120s were better in every other way in my system. I am running Revel speakers, which are known to be power hogs, and that very well could account for what I am hearing, and why I like the kt120s better.

I've been using KT120s in a Jolida and found that they're a powerful and clear sounding tube, at least compared to the 6550s and KT88s I have around, but the amp really woke up when I swapped the input/driver tubes...done for no particular reason other than curiosity. Hard to say which tubes make the most difference, output or input, or if there is some synergy going on that is infinitely variable and potentially confounding. Not much negative about 120s anywhere it seems.

Thank you Chrssain! Your post prompted me to swap out my KT-120s for the KT-77s they replaced several months ago. This was the first time I'd swapped the outputs since installing the KT-120s, and the comparison clarified my thoughts on the KT-120s and made me more aware of some positive qualities of the KT-77s. My tubes were used in Emotive Audio Vita mono amps which can use a variety of outputs ranging from the 6L6 family to the KT-120s. I ran the KT-120s at 65ma and the KT-77s at 50ma.

In my amps, here's how I would describe the tubes:

* The KT-77s have slightly more HF extension, a "sparkle" that is missing from the 120s.
* Bass with the 77s is slightly warmer and richer, also a bit looser.
* Leading edges of transients are slightly softer with the KT-77s.
* The midrange of the 77 is slightly recessed (or is the 120 slightly forward?).
* Micro-dynamics with the KT-77 are slightly better.

The above comments are what I would call objective. I am reasonably confident that someone listening in my room at the same time would agree with each of the above. On a more subjective scale, however, I would add that the KT-77s seem to be somewhat more free-flowing and less "mechanical" than the KT-120s. The KT-77s are perhaps more colored overall but are more fun to listen through.

All in all, both tubes sound great! I much prefer either of them to the GEC KT-88 for instance, and I am glad to have each of them as an option. However, I have to say that on balance I will probably go back to the KT-77 as my everyday tube.

I also have to add that my amps were not designed specifically for the KT-120. Most amps designed for the KT-120 use a higher B+ voltage that allows more power from the KT-120, but I have no idea how that would affect the sonics.