Which high power SET

Edoit, I second all of Larry's comments, including his emphasis on the word "may," except that I would add "widely varying speaker impedance" to his mention of low speaker impedance.

The fact that the speaker's impedance varies widely, from about 6 ohms at mid-bass and upper treble frequencies to as high as 34 ohms just below 2 kHz, will cause the frequency response of the amp/speaker combination to be highly sensitive to the output impedance of the amplifier that is used. Since SETs tend to have particularly high output impedances relative to most other topologies, and also because output impedances tend to differ significantly among different SET designs, the acceptability of the resulting sonics pretty much comes down to a matter of chance.

An ideal speaker candidate for use with SETs would have high efficiency, high impedance, and relatively little variation of impedance as a function of frequency. Which is not to say that results will always be unacceptable if those criteria are not met, but you would be taking a big chance if you were to buy (without return privileges) before trying the amp in your system.

If you do try out a SET in your system, given the impedance curve of your speakers what you should particularly look out for with respect to potential frequency response issues would be an over-emphasis of frequencies in the 1 to 3 kHz area. And, correspondingly, an under-emphasis of the mid-bass and upper treble.

Regards,
-- Al

In my experience, push pull has dramatically more shove than SET. 28 p/p EL34 watts isn't equivalent to 25 845 SET watts. In fact, I had 15w Quad p/p amps that were tremendously more powerful than the 25w Audions SETs. As others suggest, impedance much different between topologies.

Keithr,
I enjoy these types of discussions as they highlight the marked differences and conclusions we form. I still own an el34 PP amplifier that's 40 watts ultra linear and 20 watts triode mode. My 8 watt 300b SET literally embarrasses the PP amplifier with my speakers. This is vastly different from your experiences but that's how it goes. We all have varying outcomes. I'm in the minority here and that's okay, I respect all the participants here. Maybe I'm the oddball but to my ears SETs consistently sounds better because they are more natural and realistic. Needless to say, YMMV.Edoit "listen" to your Harbeth with your list of fine candidates.
Regards,
Charles,

Lots of good points above especially the posts by Larryi and Keithr. It is easy to fixate on the power rating and debate a 8w vs. 15w vs. 30w amp. The reality is that the numerical rating often does not correlate with how a particular SE amp sounds on a particular speaker. It is much more important to find an amp that is a synergistic match to the particular speaker. With a SE amp, it is important to use a speaker of high efficiency and easy-to-drive impedance characteristic. This is true regardless of the rated power output of the SE amp. In my case, I use a SE 46 amp which only has a little more than 1 watt output, yet it sounds much more powerful than the rating would suggest.....provided you use a compatible speaker. My speakers are around 98 db efficiency and a fairly flat 16 ohm load so they qualify as a nice match. Nevertheless, as good as the 46 amps sound, and they are the best sounding SE amps I have heard, for my tastes and on my speakers I eventually always return to my PP amps and usually find them to be a more satisfying sound overall. My PP amps happen to be more powerful (around 35 watts) and that probably contributes to the unstressed dynamic peaks but the PP amps also have more control, a tighter grip on the music. Interestingly, some people hearing both amps on my system prefer the SE 46 and some prefer the PP KT-77. There is room for both camps.

It can be difficult to predict one's preference just from reading forums like this one. You really have to live with each amp in your system for an an extended period and then decide for yourself.

I think this discussion leaves out an a couple of important factors. The first is the size of the listening room and the second is the listening level preference. The impedance curve is important as well, but to me speaker efficiency is a much lower priority. For a few years now we have been showing our 300B SET at 10 watts with Fritzspeaker Carbon 7s at 6 ohms and 87 dB. Room size was 13 x 18 or so. No problems whatsoever. Couldn't even get the amp to clip. Room overload was the only issue because we could play it loud.