kt77 vrs kt120 in Rogue M180s

I recently was a able to compare gold lion kt 77s verses tung sol kt120s in my Rogue audio M180 mono-blocks, and wanted to share my experiences with you. I did these comparisons over a period of weeks, so I think I now have a pretty good understanding of their sound in my amps. The kt77s have a little bit more air and extension in the treble, nice midrange, and very good depth, and slightly looser on the bass. The kt 120s, were clear and very open sounding, with better projection into the room with the sound stage, with less depth than the kt77, but have better width and separation. The kt120s also had better Bass extension and control over my Revel f32s woofers, They seemed to wake up the speaker, everything sounded dynamic and full. Besides the little bit of roll off in the highs, I much preferred the kt 120s in my system. Hope this helps some of you, Christopher
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.

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.
I much prefer either of them to the GEC KT-88
Salectric Do you mean the Gold Lion KT88 re-issue or the vintage Gec KT88?
The KT120 has been so ruthlessly admired and deified that I welcome any thread that chips away at the rampant cheerleading these tubes engender, although I'm firmly seated on the KT120 bandwagon. Amps not designed for KT120 somehow seem to shine with them anyway and that is simply wrong, but cool.
Xti16, Sorry, I should have been more specific. The only KT-77 and KT-88 tubes I have tried are the Gold Lion reissues. I have never heard the vintage GEC.
No reason to be sorry. The GL reissues are Genalex often referred as Gec. Just in case anyone cares the Vintage Gec KT88's are very linear. Somewhat sparkly highs - detailed minds with a good tight deep bass. Very close to the Eat KT88 diamonds. Good soundstage and imaging. From everyones review they seem to be quite similar to the KT120's. My favorite Tung Sol is the 6550 black plate. Magical mids - deep bass with a somewhat rolled off highs. Like a great EL34 on steroids. EXTREMELY musical.
I think KT120s totally suck and sound horrible. (I don't really think that, but I thought somebody should say it just for balance).
I have Rogue M180s and run them with Gold Lion KT88s. My small tubes are Telefunken. I tried KT120s and didn't care for them. There was a bit more bass but at the expense of the holographic soundstage my system normally gives. That wasn't a trade off I wanted to make, so I stayed with the KT88s.
FINALLY somebody who doesn't like KT120s! Bravo! I do think tubes tone characteristics are amp specific and I decided not to buy GL KT88s because the 120s sound so damn good (compared to my 2 other tube types anyway), but I still might try 'em since they look so cool...we shall see.
Reynolds, interesting, I was running GL kt88s but blew several tubes within a year, one took out part of my circuit board, so I was not able to do a side by side comparison, and was not so eager to re tube because of the reliability issues I had. I do remember liking the GL kt88s.
Wolf, you cracked me up!

Chris, I ordered my M180s originally with the GL KT88s as an upgrade. I've been fortunate that they've been going strong for about 3 or 4 years. I've been told that Rogue rejects a lot of tubes, so the ones they supply are supposedly better than average. In case you haven't sourced your tubes from them, that might be helpful should you decide to re-tube.
Reynolds makes a good point. I blew 2 EH KT-88 tubes in my Tempest II and called up Mark at Rogue and bought a matched quad of EH KT-90's. No more problems.
What would cause 2 EH KT-88 tubes to blow up and not 2 EH KT-90s? Don't the KT-90s put out a little more power than the KT-88s and tax the transformers more? Is it just the EH KT-90s are built better than the KT-88s?
The EH KT88s Rogue was getting had some quality issues. I don't think Samzx12's trouble with them was rare. That prompted Mark to go with EH KT90s as the base offering. It was simply related to the quality issues with the EH KT88s.

My GL KT88s were a $320 upgrade when I placed the original order. I've had no trouble with them.
Jedinite24 and Samzx12,
It was probably EH/New Sensor's fault. I think it was about 2-3 years ago when my audio dealer started complaining about a VERY bad run of EH KT88. They experienced an extremely high (early) failure rate of these tubes in that time period. Not sure if they've fully resolved those quality issues. The EH KT90 was far more reliable, even though I actually had one of those blow up (at low hours) in my amp. The KT120 have been very solid thus far.
I knew someone would ask that question lol. I should have noted when I bought my Tempest it came with 2 sets of KT88's and the seller didn't know how old they were. He didn't think one set was that old but I blew 2 tubes and the bias was set dead on. I even rechecked it several times to make sure it didn't wonder. I finally said screw it and bought a matched quad from Rogue.
OK now I see the posts above which explains it.
Thanks to you all for explaining the situation with the EH KT88s. Good to know. I've been very happy with the New Sensor Tung Sol KT-120s. No issues yet. I've seen Rogue Integrateds using the KT-120 tubes. I don't remember the models though.
Tube failure just seems inexcusable to me. I have had tubes in guitar and bass amps that suffer insane abuse relative to our pampered hifi stuff (tube "combo" guitar amps have the speaker and amp in the same exact acoustic space) with 1 tube explosion over 40 years of use. That was in my Magnatone combo in 1968. I sold it shortly thereafter for a 61 Bandmaster (my cousin's amp...he bought it new and I used it on and off until 1986). I suppose a few lazy people on the Volga New Sensor assembly line are to blame, and I assume they were shipped off to Siberia or Brockton.
I did buy my gl kt88s from Mark at Rogue, and blew 3 tubes within a year, one so bad it took out part of my board, which I was very unhappy with, but I also want the very best sound from my amps, do you think New censer has fixed the problems with this tube ?

I really don't know if the longevity of my tubes are unusual or not. A buddy of mine has an Ayon Spirit 1 with GL KT 88s, and they have a few years on them too. I can ask the guys at the shop to see if what they have to say. I will post their comments. You also might ask Mark if he's been seeing any issues with the GLs.

I wonder how robust the Shuguang Black Bottle tubes are? I have no idea how they sound though.
Put some kt120s in my cayin a100T 2 weeks ago against the advice from the distributor. They said the amp probably would not be able to push them. So far I have had no issues keeping bias and the sound has drastically improved. Mid range is soooo much better and everything just sounds bigger more powerful and very well balanced. Amp gets hot but then it always got hot with the kt88 also. To be fair I replaced the stock tubes so with comparison to a better kt88 I cannot say. I was reading and could not find any instance where the tube had damaged an amplifier so I said screw it I'm trying it. Hopefully I don't regret it later.
My personal crusade to catalog KT120s destroying a transformer or damaging an amp continues...so far all of the transformers all over the world are surviving, including my Jolida 502p after thousands of hours over a year and a half. But I remain ever vigilant!