KT-120s in a c-j Premier 11A

Has anyone tried the KT-120s in a Premier 11A amp? I've used them in a Premier 140 with no issues and liked how they sounded. I was wondering if anyone's tried them yet in this older model. When I called c-j months ago, I'd gotten the usual party line about their techs recommending not using anything other than stock tubes in the 140.

Thanks in advance.
When I called c-j months ago,
Try calling them again. From what I've read a few AR amps will not work with them without significant power supply modifications. But most do and are NOW approved. As far as CJ they may have tested more models than when you first inquired. Personally I would not not drop in tubes the manufacturer did NOT approve for that model. Could make for a very costly repair. BTW I believe today CJ approves of the KT120 in the 140.
cj is as far as I know, now using the KT120s in place of the 6550s. I just recently retubed my ART with 16 of those suckers. I think part of the issue might have been that cj wanted to burn through their existing stock--since if you look at the KT120s, their date code is 2006.

Took your advice and called c-j and got Ed's voicemail in customer service. Left him a message about wanting to use the KT-120s in my 11A but haven't heard back from him yet.

If I do, I'll post his response.


I've used the KT-120s in my Premier 140 and didn't have any problems but the 140 is currently out of commission which is why the 11A is back on active duty. Since it's an older unit with aging parts, I was hesitant to just plug in the 120s without getting c-j's blessing. I hope Ed gets back to me before I do something irresponsible like just try them out.

I took a look at your system. Wow! I'm sure it sounds just wonderful.

Thank you both for taking the time to respond to my query.

I went ahead and tried them in the 11A. They've been running about 7 hours now without any issues so far. The transformer casing may be running slightly hotter than normal or it could be just my imagination. They sound pretty darn good: kind of a cross between the richness of a KT-88 and the detail of a 6550 but not to the full extent of either.

For a current production tube, they're quite good. Not a vintage Tung-Sol but then what is, except the original?
Glad they are working out. I'm tempted to try them someday. I was lucky to score a couple of quads of the original TS solid black and grey plates. Extremely musical (lost a little detail compared to current production 6550's) and I'll admit the black plates are my favorites out of the 2. I'm using some current production Eat kt88's right now and they are super excellent but they come with a heavy price. Also the Eat's don't seem to be too reliable - lost 2 already :-( but I did buy them used.
I agree regarding the Tung-Sol black plates. If I had to pick just one tube to live with from now on, that'd be it. The solid and three hole grey plates aren't too shabby either.

I've never been lucky enough to hear the EAT KT-88s but their reputation precedes them. They're as expensive as vintage Tung-Sol and Genalex though.

We'll see how long the KT-120s remain in the 11A before audiophilia nervosa sets in and something else replaces them.
Hi Joe

How are things going or How did things go with the Tung Sol KT-120s and your C-J 11A amp? What are your listening impressions with those KT-120s in place? I hope your amp wasn't harmed with having those KT-120s in there. Some members were saying in older amps there could be damage severely inflicted to them if the KT-120s are used.
Hi Jedinite24,

I had them in the 11A and they were never an issue. I did eventually get a hold of c-j customer service and was told it was okay to use them. Although they run at a higher heater current (1.8 amps) than most current production tubes, the 11A was designed and voiced around the GE 6550A which runs at the same heater current. Vintage Tung-Sol 6550s also run at 1.8 amps and I'd previously had both the T-S 6550s and the GE 6550As in the unit without any issues.

conrad-johnson is now supplying all of their current production amps with the KT120 and both Lew Johnson and Bill Conrad have both been quoted as really liking this tube. That opinion seems to be shared by most c-j owners, too.

I like the tube, but it seems I'm in a small minority of users, maybe just me, actually :) who prefer other tubes in my c-j amps. The New Sensor Tung-Sol 6550 and New Sensor Gold Lion KT88 being two current production output tubes that I prefer.

The KT120 is smooth sounding with excellent imaging. It has a solid bass response and the treble is generally also good. However, I find it a little lacking at the very top and in my opinion, it also lacks a little of the upper midrange, lower treble clarity of a good 6550.

Just my opinion naturally and I want to restate that I seem to be in the minority.