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

I wonder if the output transformer of amplifier with the triode/UL option is optimized equally for both modes, or if the default is to design for best operation in UL, then simply switch the screens to pair with the plates of the output tubes (usually via a resistor)?

@pickindoug To do it properly, the output transformer would have to have taps for triode operation since the optimal plate to plate load for a power pentode wired in triode is a lower impedance than that used for UL operation. That could make the transformer a lot more expensive and the switching a bit more complex.

:) and now that turns out to not be your experience. Kinda makes my point.

I am not arguing with what anyone is saying; I have stated before that I am illiterate on these subjects.  I was simply directly quoting from the owners manual that came with my amp when I bought it.  Although he didn't write it that way, is it possible that what i quoted was meant to only be applied to triode operation?  

@immatthewj I was commenting more in the fact that the manual was either poorly written or misleading. I doubt the 'triode only' thing since it is a UL design. The best interpretation is there's no global feedback. But there certainly is local feedback.

I just took a look at the specs listed in the V12 owner’s manual and under feedback it says "zero."

@immatthewj UL operation is feedback FWIW. To know how much you'd have to compare to pentode operation, which isn't an option...

@immatthewj You don't have to dig deep on this one. The Dynaco ST70 is arguably the most famous ultra-linear amplifier made although all the Dynaco amps were ultra-linear.

Meaning that I guess he probably "voiced" the V12 in triode, but for at least the present moment, I am preferring UL.

@immatthewj IMO 'voicing' is a bad practice. I very much doubt this amp was 'voiced'.

I think the term ultra linear is marketing in nature and I dare say most people have no clue what they’re buying when they do.

@emergingsoul The term 'ultra-linear' was used to describe the invention that is the subject matter of US patent number 2710312A. You'll see it used in the text of the patent. Its an accurate description of  the time about a break thru in amplifier technology. Diagrams of how it works are at the link.

Loudness controls have to do with how the ear's frequency response changes with volume. Its a tone compensation.

WRT UL, It can be made switchable by having a switch connect the screen of the power tube to its plate as opposed to the tap on the output transformer.

Its not a marketing term any more than the word 'triode'. Its part of engineering lexicon.

So if the manufacturer spends the extra money for a UL winding they would, seemingly, have optimised it for the tube type and circuit.

@viridian This assumes that the manufacturer knew about the patent and designed according to it rather than the tradition that developed trying to get around it. In a way, David Hafler might be the one responsible for that; he was one of the inventors when he was at Acrosound, to whom the patent was assigned. When Hafler moved to Dynaco the patent didn't go with him but he knew full well how to get around it. So its reasonable to assume that Dynaco OPTs are not optimized.

So a rational thinker, in possession of that knowledge, might conclude that the UL taps were improperly placed, causing the triode setting to work better. However, a rational thinker might also wonder if the OPT had windings to accommodate the difference in the plate load impedances required since that value for a given tube is different for a pentode as opposed to the same tube wired in triode.

I'm certainly wondering that. Whether I'm a rational thinker is another matter.

but in the manual for the V12, Dennis Had is saying that tubes that can be roled in this amp include;  6L6, KT88, 6550, KT90, KT66, "even 6V6."

Again, with not intent of being argumentative, does this sound incorrect? 

@immatthewj Not exactly. But its likely that one tube type in that list will perform better than others. That's a bit different from saying that it will 'work'; sure it will play but the output transformer should be optimized for a particular tube.

@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.

@immatthewj If the UL taps are set up properly, the amp should have less distortion in UL mode. FWIW, this was well understood in the 1950s when UL was first patented. Distortion obscures detail; so if the output transformers are properly designed it should be no surprise that the UL mode sounds better.

A secondary aspect of this is power tubes in UL mode are easier to drive than the same power tubes in triode mode. So the amp very likely is also making less distortion on this account too.