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

@immatthewj you were pretty close on your thoughts and memories of the Mesa Baron amp. Appears that amp delivers 150Wpc in full pentode mode, 120Wpc in 2/3 pentode, 85Wpc in 2/3 triode, and 60Wpc in full triode.

Ask: so, which of the switch modes did you enjoy most with the Mesa Baron amp?

And yes, Triode, UItralinear, Pentode (hybrid) and full Pentode will all sound and present differently. Note - your Cary V12 and SLA-70 amp experiences with each of their own circuit designs Dennis Had created will have their own signatures as well. You know, and have heard it for years. It’s fine to just stop there and enjoy it too!

Hey, give yourself some credit here - based on how you’ve reported things so far, I tend to think your hearing and ability to discern differences might be just fine. Here is the key - you are hearing the differences now, and hats off to you for that!

I remember after messing with different solid state mosfet based amps for 30+ years, searching for that same lush sound, I eventually expanded into tube amps in parallel. I had all of the same [renewed] questions you have right now about the differences in sound with different tube amps, circuit designs, switch modes, and related tubes for each. As I reflect back, wow, had a lot to learn and still do, trying different things as you are now. Note: I got help from a few local tech legends and mentors, sharing their gear & tubes. Both upgraded my former tube and SS amps. 

Like you, and your V12, my modified V12R turned me into an EL34 tube geek. The Triode / UL switch gave an idea about both modes. And so did the SLI-80 with KT88s, which was an extension of your SLA-70, with the integrated front end and KT88s. Again, each of these amps and their own type of sound. Precise, maybe not, yet it might be a sound you prefer. I went through Cary, Inspire, and others trying it too. Worth every step along they way and appreciated every moment.

Welcome back to re-discovering circuits, designs, tubes and different applications through hearing the "differences". Probably the most important aspect to all of it imo.

If I may suggest, there might be a "next chapter" for you in your discovery, possibly moving to now try a (non-switchable) dedicated Ultralinear amp(s). Then trying a dedicated (non-strapped, true single ended) Triode amp with actual Triode tubes. You will hear all new difference yet again, in different ways, if you decide to try it in the future. Enjoy the renewed discovery and journey!

Every amp I have owned that was switchable between UL and Triode has sounded better in ultralinear mode, no matter the speaker efficiency. The only way to truly get the triode benefit is to have an SET amplifier and appropriate speakers.

I can only speak to the Manley Labs 200/100 triode switchable amps that I have used for quite some time.  I would imagine triode switchable amps do not all behave the same; in no small part due to the speaker they are driving and, importantly, what the listener considers to be “better”.  For those reasons I am suspicious of blanket statements about this issue one way or the other.

In the case of my Manley amps and the speakers that I have used them with what I hear is the following:

Triode mode:

- Tonally more refined.  Slightly smaller, but better organized and delineated soundstage.  Slightly smaller, but better defined individual images.  Overall, better clarity.

Ultralinear mode:

- More powerful and deeper bass range, but somewhat less detailed.  More bass “volume”, but less of the sound of the bow and rosin.  Slightly larger soundstage and correspondingly slightly larger individual images.  Depending on the music played, somewhat better musical drive (PRAT).  Darker, slightly thicker, even murkier overall sound.

When in my listening chair (usually Classical and acoustic Jazz), Triode is “better” for me.  When listening away for the sweet spot (usually Rock/R&B), usually at louder volumes when working out or other activity, Ultralinear is more satisfying (better?).  

@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.

I readily admit to how illiterate I am when it comes to electrical. Actually I had always thought that the one was a synonym for the other. I am in need of an education. Can you put into layman’s terms the difference between the three? If layman’s terms just won’t work because the subject matter is just too complex and it would take writing a book, I understand. I can live with just knowing that today I liked UL better today.

@immatthewj I’m no circuit analyst or electrical engineer, so I’m possibly not the guy you need to hear this from. But I’m a computer programmer who often has to explain things to people with a tenuous grasp of coding, so I’ll give it a crack lol. Based on my limited understanding, what differentiates a tetrode / pentode (call these both "pentode" from here on out, as the 5th element is not relevant to this discussion) from a triode is that the former have a screen grid that triodes don’t. The screen grid is positioned between the control/signal gird and the plate (the biggest metal part you see in a tube). You can sometimes spot it through the plate holes - its coiled wire is spaced out much more than the tighter control grid coils.

When you run these amps in "triode" mode, this screen is tied directly to the plate, and basically acts like it isn’t there (mostly). When you run them in "pentode" or UL mode, the screens are wired to the output transformers, but these 2 modes differ in exactly HOW they are wired to the transformer. Basically, UL is more cleverly done so that its distortion levels are much closer to triode mode than pentode (lower is better) and its power output is much closer to pentode mode than triode (higher is better). So you really do get "the best of both worlds", sort of. The output transformers do need to be designed with UL mode in mind for this to work. But frankly, it would be very odd to encounter an amplifier with only a "pentode" mode instead of UL (UL mode was devised in the 1930s and became common since the 1940s, e.g. the "Williamson" amplifier - incidentally, every time I hear of that "Wilsenton" Chinese amp brand I think that must be an Engrish-mangling of the name "Williamson"!). And those which offer switchable triode vs. "pentode" modes should also be rare - in those cases, you should probably just stick to triode. The only meaningful choice is triode versus UL. And in my opinion, borne out by when I’ve tried this - if you’ve got tetrode / pentode tubes running in your amps, you really want to be running UL mode. That’s the best use of their design elements.

True power triode tubes, DHT, and SingleEnded (these 3 often go together but not always!) are other balls of wax - I’ve heard them a couple times and don’t think they are for me. At least, I haven’t been won over yet. I listen loud and feel like I benefit too much from the extra power of UL mode. Give me tubes which slam, or give me solid state! (that’s better than death, I guess)