Why not more on 845 SETs?

I personally think that the additional power in an 845 SET is not necessary. But, I guess that if someone wants to power some less-efficient multi-driver loudspeakers, it would be useful

What I would ask about this is, why would someone want to use a SET amp, and then drive inefficient multi-driver speakers with it? Perhaps I'm in a fog here, but I thought that the purpose of a SET amp was to provide coherence and purity of tone and harmonics. If you take the amp's output, and chop it up into bits and pieces in a phase-shifting passive crossover network which also causes other distortions, and eats up power and detail, use different drivers which inherently have different radiation source points, sonic characteristics, and dispersion patterns, and introduces odd-order harmonic distortion to a previously(primarily) even-order signal distortion profile, are we really getting what we wanted to get? I don't think so. But we will get what approximates a reasonably flat response test curve, as long as the output impedance is significantly enough below the speaker impedance curve to avoid reactive effects on the amp's response curve(not likely). What we really get with this kind of combination, is the relatively high even-order distortion profile of the amp, added to the even-order and also the easily discerned odd-order distortion profile of the multi-way speaker, making system distortion higher than necessary, and also in content(odd-order)which spreads out all over the spectrum, instead of primarily at the 2nd harmonic. In the case of lower efficiency, lower impedance(4 ohm) multi-driver speaker sytems, we can add the practically total loss of damping factor and cone control, and making the amp's freq response curve fluctuate with the speaker's reactive impedance curve, and add this to the inherently low internal damping ability of the less-efficient speakers, all causing bloat, flopping around cones, no tonal accuracy, and wild frequency response, added to all the other problems. Why someone would want to do this is beyond me, except maybe that they are after some deeper bass response at the significant expense of purity in the rest of the spectrum.

IMO, an efficient higher impedance single driver system is what is best with a SET amp. In that case a small 45, 2A3, or even 300B is fine.

If you want to say the 845 is better for deeper bass, fine, but I contend that it is not enough power for deep bass, and probably would require a powered subwoofer or powered woofer anyway for that purpose(another seam).

The issue is what is the goal of a SET system. Is it to simply provide a Class A amplification source, or is it to be something more than that? That's for the user to decide.

IMO, a SET amp can be much more than just a Class A amp. It can provide a distortion of predictable and less-invasive profile, that can be effectively utilized to work in a complementary fashion with certain loudspeakers, to create an overall system distortion profile of primarily easy-on-the-ear even-order harmonic distortion located in a fairly narrow range of the 2nd harmonic area, and nearly eliminating any of the problematic odd-order distortions which are so much more discernible to the ear that only extremely small amounts of it can be tolerated. Additionally, with the "certain"(single driver) speakers, it can deliver the sound from the amp without the inevitable multitude of problems associated with mainstream multi-driver speaker systems. Sure, single drivers have issues too, but delivering pure coherent high-detail sound with mostly even order distortion products at one area of the spectrum is not one of them.

My caution is thus, when you make a decision for a component, is it not a good idea to make the most of what it can do(as a whole), instead of trying to "shoe-horn" it into a more conventional role? I think so. The conventional wisdom of choosing a higher power amplifier, in order to make a wider selection of speakers possible to use(multi-driver), actually can lead you into a snafu which would not have been easily stepped-in with a lower power SET amplifier. The very fact that the low power SET amps practically forces you to use a high-efficiency single driver system(or horn) is actually a good thing, and not a limitation. The low power of the amp is actually almost "forcing" you to make the right decision. When higher power is available, then you can step right into the crap, unless you know what you're doing, and why you're doing it.

If you want to use an 845 SET, and you like it, that is fine, and there are some really good ones out there. However, there is alot more to a SET amp than how many watts it has, and whether it provides Class A amplification. With this type of amp, we can go beyond the mainstream, and get more than is typically available from more "normal" amplifier designs, if we study what they do and how they interact with various loudspeaker designs.

If you take a look on the web, at an article called "Why Single-ended amplifiers?"" by Audiopax's designer and engineer Eduardo de Lima(http://usuarios.uninet.com.br/~edelima/REASONS.htm), you can see his testing, graphs, and descriptions of the interactions that I mentioned above. He even shows how careful phase alignment of the speaker and amp output can work to reduce overall system distortion to below what any other type of package can produce, by using this type of combination.

I know this is a "radical" concept, but there can be more to things than easily meets the eye.

Twl, you seem to be writing off the use of SET amps with "conventional" speakers and I think this is needlessly restrictive. This is, or was, certainly the conventional wisdom and helped keep me from enjoying SETs for a long time. Then I discovered that certain speakers, despite their moderate sensitivity levels , were extremely SET friendly. Examples of such speakers from my personal experience are the ProAc Response 2, Response 3, Gallo Nucleus Ultimate, and Gallo Reference 3 (my current speakers). How can you tell which conventional speakers are going to be "SET friendly?" Well, you can start with something in the 88db sensitivity area whose impedance rarely or never dips below 8 ohms and whose crossover networks are very simple, but mostly you have to listen and see (or rather, hear). I'm sure glad I did. Dave

Perhaps a SET amp would perform best with a single driver speaker if one were looking for the simplest path, but that does not mean that it won't sound excellent through a dynamic multiple driver speaker. And with a single driver speaker you may not get much bass and I can tell you the bass the Ios/Trentes is deep and tight! I thought of this analogy: with some amps the Trentes are like a water skier being pulled by a sluggish boat; they just never get up and going. But with the 845-based Ios the Trentes get up, go and sing like a slalom skier on a glass-smooth lake at first light. Beauty, eloquence, dynamics.

The Gallo Nucleus Reference 2 (with full InSound/OmegaMikro upgrades, no crossovers, three 6.5inch Dynaudio drivers wired in parallel for 9ohm impedance, OmegaMikro wiring throughout, [?] 330 degree CDT tweeter, which more closely matches the dynamic drivers for radiation patters, and time aligned, 9ohm, 90dB/w/m) coupled to Viva Verona XL 845 tube amps (26wpc) has to be the best "all-rounc" performance I've heard from a SET system to date! This was for both full symphonic orchestral music as well as electronic "rock." It had a full, rich, immersive, and immediate sound.

I've heard a few other demos with 845 SETs. Each time I wanted to "not like the sound" as I _*knew*_ the sound should be less pure than a lower powered tube like a 45, 2a3, or 300b. But so far I haven't heard an flea powered system that I've like as much as the two 845 systems I've heard. I did go to MAF one year, but show conditions are only so good. I really could't draw conclusions in that environment. But without hearing a 845 SET, I would have though (on paper, with no first hand experience) exactly as Twl does. Maybe if I listened to more, properly set up flea powered systems I would think along the lines of Twl. But for no, I can't given what I've heard.

But I still covet that gallo/845 system. I was a good balance of positives with a healthy balance of negatives that I could tolerate long term. If only I could afford such a system!

Dave, not really "writing them off", but just mentioning that there can be some things that go beyond what is normally expected.

I'm not saying that single-driver speakers are for everybody, but I am saying that there is a certain synergy between them and SET amps that can be very productive if used properly. I know that single-drivers are frequency restricted mostly in the bottom end, and that alot of people cannot abide that restriction. However, when going to multi-drivers, some of the really good things about a SET amp are somewhat deteriorated, due to the things that happen with multi-drivers.

I really probably should have worded my post a little bit softer, but I do feel pretty strongly about this issue.

That said, I have no aversion to people using SET amps with multi-drivers themselves, if the users prefer that option. After all, it is what the individual prefers, and not me, which is the critical issue with each person's system.

I guess what I'm trying to say is that in my opinion, there is more to be gained by a good match in the amp/speaker combo with a low power SET/single-driver, than there is from having the higher power SET and using multi-driver speakers. In effect, having a low power SET with high-efficiency speakers will allow the same/similar SPL in the room as a higher power SET with lower efficiency speakers. So the listening level issue is somewhat moot. What's left is the sound quality, which IMO can be better by using a scenario as I outlined above, which can yield an overall system distortion profile that is audibly more palatable than other type while still yielding less signal losses(thus preserving the musical detail and life). Doubtless, some will disagree, and that's fine. This is just my point of view.

I don't expect everyone else to subscribe to this, and certainly am not suggesting everyone should. I'm simply pointing out an interesting factor that might be important to those trying to extract the most information out of their system, with the least objectionable results(from my point of view).

Your description of "SET friendly" speakers seems to be a good one. I'm sure that they all work fine with a moderate to high powered SET, and would sound great. I'm glad that you are enjoying the "SET experience", as I am.

As always, I'm just trying to make subjects for discussion here, and not making any "rules" or "judgments" about anyone else's system preferences or opinions.

IMHO, and YMMV.