Looking for advice on these speakers

I'll second all of Charles' comments, and Gsm has provided some valuable perspectives as well, IMO. And although I've had no experience with Rogue products, yes I would suspect that going to triode mode on your 180's is shifting their sonics at least slightly in the SET direction.

I've had two amps that were switchable between the two modes, the classic and highly regarded vintage monoblock Marantz 2's and 9's, from the 1950's and 60's respectively, both of which I owned about 20 years ago. Both were EL34-based, with the 2's rated at about 20W/40W in the two modes, and the 9's at about 35W/70W. In both cases I much preferred the richer and in other ways subjectively better sonics of triode mode. Although the 20 watt triode mode capability of the 2's was inadequate on some recordings with the speakers I was using at the time, rated at 90 db/1W/1m and having fairly easy to drive impedance characteristics. In that mode with the 2's I actually caused the power tubes to arc and flash brightly a couple of times on Telarc bass drum beats, although no damage resulted. I don't recall having any problems with 40 watts.

BTW, a point of interest: In principle, if implemented in a certain way UL mode is capable of providing the sonic benefits of triode strapping, while providing considerably greater power capability at the same time. See this post by Atmasphere. You'll also find in that thread some varied reports of experiences comparing the two modes. As usual, implementation of the specific design seems to trump all.

Best,
-- Al

Al, I may have asked this question some time ago.

The output stage coupling of most ARC tube amps, at least my Ref 150, "is a combination of 'ultralinear' and Audio Research’s patented 'partially cathode-coupled' topology, which is superior to conventional pentode or triode operation." The foregoing cite is off of the ARCDB web site link to the Ref 150.

I have absolutely no idea what ARC is talking about, but suspect it may be a form of local negative feedback of sorts. ARC also touts that its circuit topology makes for better performance than "conventional pentode or triode operation." No comment.

I mention that here because of your last several posts which recommend caution in using some very low power SETs, especially if the amp will be called upon to drive dynamic music. Certainly, there are higher power amp options that may get one close to the presumed benefits of a SET amp, e.g., Ralph's zero NF OTL amps, or VAC amps, etc.

Maybe you can push the fog away.

Hi Bruce,

Yes, as Ralph had indicated here the ARC topology you are referring to is indeed a form of feedback. I have no idea, though, if that topology would cause the resulting sonics to be to some degree more SET-like, or if its presumed benefits might be in some other direction.

Best,
-- Al

I'd suspect that a circuit that is reliant on a feedback loop(as Ralph described) is not in the direction of SET sound (generically speaking). One of the "major" attractions of SET amplifiers is their simplicity and lack of need for NFB. Now which direction one chooses to follow is certainly individual choice.
Charles,

Al and others, I appreciate that adherents of low power SET amps believe, and perhaps with some justification, that the benefits outweigh the downsides (e.g., low power output).

My only point is that opting in favor of that direction necessarily limits the universe of speaker options -- that is, speakers having high sensitivity specs. I'm not sure if SETs also have high'ish output impedances, but if so, then other trade-offs may be required.

I for one like flexibility and options. My bias (pun intended) would be to shy away from this class of amps.