I hate to say it, but now I think maybe I like my amp in ultralinear mode versus triode

I was just pulling your leg. Its a bad habit I have.

@artemus_5 , you asked a legitimate question--I didn't take any offense to it.  After all the time I spent swearing that triode was a superior sound, I hated to admit that after yesterday I feel that I may have been mistaken.

Everything was great at first then after a couple months the problems began, when I would turn everything on after a hour the amp would make the most awful load noises like metal bending and it was loud. That went on no matter what I would do,there was no support to help me…it was one of those things you could not find, then after a year or so the stock tubes started shorting out, getting that red light on start up, and fuses blowing at the same time…the wife and I would look at each other when I turned it on, holding our breath..the sound with the Fortes was ok not great

@silverfoxvtx1800 Ooof! I don’t know how on earth you had so much patience and/or capacity for self-abuse on that front! Months...a year later? I would’ve hit my tolerance limit at or before "a couple days" at most. If I thought my speakers were at risk it’s not going back on, period. And if the dealer / distributor / manufacturer aren’t willing to assist (sounds like a lemon unit), then frankly it’s going in the trash - and I'd let plenty of fellow audiophiles know what I think of said dealer / distrib / manufacturer. And then you say it didn’t even sound that great, to boot! Life is short man - find something else that brings you joy.

@mulveling , thank you for taking the time and effort to type out that explanation. I am going to print it and try reading it slowly and thoroughly to digest it. I think that you probably did a good job, I struggle with electrical. When I was in HS the Air Force recruiter told my mom that I did "real well on electrical on the ASVABs." I don’t believe that he was telling her the truth. When I finally did go in a year later, they were, "Sorry, son, electrical is full--how about open mechanical?" (Meaning airplane grease monkey.) Probably a good thing electrical was "filled up." I doubt I would have been good at it. Anyway, I think you are right about "better than death."

@atmasphere , thank you also for the explanations. I was pretty sure you would have a handle on this stuff. I now wish that I had gave UL a SERIOUS whirl (as opposed to the short try outs or ear bleed sessions) before this. Not that I didn’t like my amp in triode, but now I am thinking it is "more better sounding" in UL. Thanks again for the feed back.

UL mode is a pentode in "partial triode" mode. The screen and plate are operated at the same voltage and when the screen is tapped at the load (plate) it's triode mode and pentode mode when the screen is tapped at the B+ of the transformer. In between the two is the UL tap (about 40 to 43% of the winding) and that provides a negative feedback to the screen, resulting in lower distortion in push-pull operation.

I have a KT150 P-P. In UL mode it sounds like a solid state amp -- clean, tight transients and excellent bass response. In triode mode it's a little more syrupy and tube-like. I prefer the triode mode.

@gs5556 Your explanation is partially correct. The bit about 'partial triode' is not. What UL allows is for a pentode to have better linearity than a triode.

However there's been a wrinkle caused by the fact that the UL technology was the topic of a patent. To get around it, other manufacturers moved the taps away from the ideal point as taught by the patent. The linearity goes down rapidly. The patent also taught there was an ideal percentage for the tap that depended on the power tubes being used, which is why you can't use the same output transformer with EL34s and 6L6s unless there is a tap for each tube type.

The use of the incorrect tap has become a tradition and is now so ingrained that everyone thinks 40-43% is the right ratio; so UL operation it typically incorrect. I think that's part of why you see debate around 'UL vs triode' in high end audio. Depending on the amp, triode may or may not be better as a result. So its good in the case of the original post that the Cary seems to have gotten this bit right.