SET 45 Amp Driving Dynamic Speakers


I have an Antique Sound Labs Tulip SET amp running Emission Labs mesh plate 45s, driving Audio Note AN E speakers. It will play WAY louder than I want to listen, and the dynamics are amazing with all types of music.

Why do I keep reading that 45s (and other low power triodes) are only appropriate for horns, or other super efficient speakers? I think a real disservice has been done to the audiophile community by the propagation of this idea. IMO, anyone who prefers to listen to music at sane levels can enjoy the many benefits of a low power SET amp with carefully chosen dynamic speakers.

Anyone else feel this way/have similar experience?
tommylion
Yes, here we do have a profound disagreement. I even believe that only analog tape sounds right. Many do too.
Inna,
I understand your position as this debate is discussed to the point of Ad nauseam (and this is unlikely to change). So in this case we respectfully agree to disagree.  Both sides of this argument have plenty of company 😊😊. 
Charles, 
Seems more than a few running 45 SET with under 100db loudspeakers are saying they do not listen loud and are limited in music selection. If you want few limits with 45 SET want to play any type of music you care to you will most likely need a horn loaded loudspeaker and might even have to biamp. Or enjoy within limits nothing wrong with that but I do feel those insisting that the suggestion that 45 SET needs hi-eff is wrong because if they use within limits it works for them misses the point of the over 100db easy ohm load suggestions for 45 SET use and that is to get the best out of these SETs.
If using a 45 amp to only reproduce 350 to 2000Hz on a 100 dB/W driver in a 25m2 room and if average listening level is 85-90 dB SPL, would a 45 suffice or be driven to the point where 5th order harmonics become an issue?

Al did an excellent job of answering this.

Since the type 45 can operate with exceptional bandwidth, I would have considered this amplifier to be a good one for the tweeter, where high power is usually less of an issue. Alternatively, if you could operate a mid-range driver with more efficiency, then you would also have a good payoff.

Hello Al.

Thanks for the excellent and thoughtful reply. I've gone through it several times in the last couple of days.

You made it very clear so I can work through the tradeoffs. Maybe running the amp up to 50% si not as offensive? Something to try and learn.

I think most of my music is going to be rather compressed. Of course I have some good recordings, including Telarc's Firebird you mentioned, but the majority of my listening is going to happen with lesser quality recordings. Let alone having 3 kids into teenagehood and wanting to share some listening time with them, with their music ;-)

FWIW, I'm working on the midrange driver. It's a horn-loaded cone, so efficiency is yet another tradeoff in the design. I believe 100dB/W is about a floor, and probably a cieling around 106dB/W. Hopefully I can get it to 103-104dB/W and then things start to look significantly better. Or I'll have to settle for a 2A3 or higher power amp.


Glad to see a healthy thread develop on SETs. I'm hoping that eventually more people will be open to try what well-implemented DSP can do for a system (emphasis on "well-implemented"), just like Charles was open to experience well-implemented digital. Not saying it will be best for everybody, but I find it a pity people follow so many preconceived notions in audio and preclude themselves from trying new things. OK, time to get off my soap box :-)

Lewinskih01,
You have the right attitude and I wish you well. Sometimes you have to ignore well meaning warnings based on preconceived notions. When I became interested in SET amplifiers the warnings were, limited music genre, pleasant but very colored midrange, very little  bass or high frequency information. All were completely wrong and in hindsight total nonsense. The past 7 years with my SET 300b based system  has provided the most  vibrant,open,transparent, organic and emotional involvement I’ve ever experienced. I wish you the best of success moving forward with your project.
Charles,
I've often been amused by the comments in Stereophile about how an SET can measure so poorly and yet sound so good- and further that no-one seems to know why. I have to assume that they did not ask any designers when that comment was made.

IMO low distortion is pretty important, and as long as you don't push them hard SETs can have distortion lower than any solid state amp. And when you ask a little more power, you get the 2nd harmonic which is a lot less offensive to the ear (even in large quantities) than the higher ordered harmonics of solid state! So its no surprise why SETs have a following.
"Sometimes you have to ignore well meaning warnings based on preconceived notions. "

How someone thinks something sounds good or bad is a notion.

Technical facts are facts however, not notions. You can choose to ignore them but chances are higher you may regret it later if you do.


That’s not to say technical facts tell the whole story either. They do not. But they do set the foundation for how the story is most likely to end.

I’ve only heard SETs with horns at an audio show. I recall an Art Audio amp with PX25s driving Avantgarde speakers (Duos?) that sounded REALLY good. I don’t doubt that 45s et al can sound even better with horns.

What I am saying is that those who don’t want horns (for space, budget, WAF, or other reasons) can still get a lot of the virtues of SETs with well matched, higher efficiency, dynamics. That was not at all the impression I got before trying it for myself. I know there are always trade offs, but, in my case, I have a hard time perceiving any significant ones.

Horns are not an option for me, at least right now. Maybe there’s an amp out there that can give me the the "magic" of my 45s AND greater dynamic headroom, with my current speakers. I’m not chasing after it, though.
"Technical facts" by no means tell the entire story.  As has been mentioned on this site numerous times,  measurements and specifications play a fundamental role primarily in determining electrical matching/suitability of audio components.  So it is an effective screening tool. I'm unaware of anyone here disputing this point. What determines if someone will be happy with chosen components is listening to them following the initial screening. It's a two stage process. For my purposes listening is required to make judgements regarding the merits of audio products. Others may utilize alternative methods. 
Charles, 
Tommy,

I’ve heard all forms of demos at shows also, including very expensive high quality SETs using similar very large efficiency horns (with correspondingly stunning results).

The best thought out and executed ones, SET or otherwise, always exceed those that are compromised in some way.

Because of the few watts used, the difference between the best (large GOTO custom horns and bass bins comes to mind) and worst (Zu Essence is one that comes to mind, fine for acoustic jazz, very meh for rock/pop) SET demos I hear are perhaps among the most extreme possible.

So the ante is upped whenever one device asks more of another. That can be a SET asking more of the speakers (be more efficient and an easier load) or the speakers asking more of the amp (give me lots of clean undistorted power please).

Lots of ways to skin the cat acceptably perhaps but only only a few ways to really do it right/best.

I feel I’ve done it pretty well the second way currently at home (compared to the stellar SET demo for example I have heard as a reference among others) and look forward to giving the other way a try someday starting with a separate system on a smaller scale that I can compare and contrast with my in home larger "reference" system.

In the end its all a matter of expectations and how well things are executed together to meet them.






I don’t know of anyone who begins their entry into High End audio with SETs.   Most everyone I know who enjoy these amps tend to be very experienced and have owned quite a few different amplifiers before hand. This scenario would certainly describe my journey. Having gone through various good quality SS and push pull tube amplifiers helped me quickly recognized the significant attributes of a SET. Tommy I suspect that the 45 SET I isn’t your first amplifier.
Charles,
Charles,

I suspect there is a significant sized yet small minority out there that do venture into SETs or their like initially for various reasons, but on a limited budget like most first timers.

FOr example Glow audio sells a very popular and stylish looking SEP amp, the Amp 1 that will look quite nice in many homes. I’ve heard it at shows and it works quite well with many speakers. Jolida has various low wattage tube amps (not set) that also sound quite nice, like the FX-10 that I ’ve also heard.

These are very viable but well "compromised" options like all the rest for similar cost that some newbies might consider right off the bat.

The thing is speakers for an uncompromised set system tend to be larger and quite expensive and not something that will appeal to many.

Whereas with newer Class D amp technology in particular, one can create a small, manageable and reasonably uncompromised system quite easily with many options and for fairly modest cost.

Again, its all a matter of expectations and what limitations one is able to deal with effectively.

When it comes to tube amps, for me the fewer tubes the better. That’s where a SET amp has appeal for me. Thing is my Class D based SS system sounds so good, I have little incentive to look elsewhere other than sheer curiosity and the fact that I think this stuff is fun. I’m very glad I tried the Class D option first. So is my power bill. I’ve opted for modern technology that is also more efficient and green (and also best match my speakers around which my system is built for best results) than older amp technology that is the exact opposite and requires things be built around it for best results. :^)

Either way is perfectly valid and of course neither will appeal to all which is what makes the world go round.






I think that most often people who are SET fans arrive at that point after going through a range of other choices.  Low-powered SETs tend to be an end-point only after a long search because it takes some experience finding the relatively few speakers that are compatible with such amps (many high-efficiency speakers are highly "colored" as far as their tonal balance so you have to find the few that are not so odd or learn which "color" works for you).  It can also mean giving up a little on some of the more obvious attributes (like extremely deep bass response and bass punch) for the more sublime attributes of SET amps and compatible speakers that one learns to appreciate after long-term experience.  So, in that sense, I agree with Charles.

But, in this day and age, where "knowledge" so freely flows on the internet, I can see Mapman's point that a lot of inexperienced listeners could be seduced into trying SET amps at the outset (it took me YEARS before I even learned of their existence, today just google "best amp" and you are there).  I fear that it is the case that many are tempted to try SET amps with incompatible speakers and/or assume that cheaper SET amps will do the trick because they should not cost that much to manufacture (because they a simple and have few parts).  The problem with that is that those parts can be very expensive to get right, particularly the large, air-gapped output transformers that can handle the high standing current in the primary without over saturating.   You will find a lot of internet posts from those saying that the SET amps they heard are crap; I bet that a lot of this comes from listening to such "bad" setups (easier to be WAY wrong with SETs that with any other kind of amps).

While I agree that it is far easier to get quite decent sound at a reasonable price from Class-D amps, I have not heard any "all out" assaults on top quality sound that involved such amps.  I admit that I haven't heard too many in high-end systems utilizing Class-D amps, but, those that I have heard were somewhat disappointing (e.g., Devailet and Rowland) because they just sounded a bit dull and un-engaging.   In a lower-end system, I thought that a Bel Canto amp sounded pretty good for the money.
Hi Larry,
There could be a few newbies to High End audio who begin with SETs  (admittedly I have not done a survey) . As you correctly acknowledge it more often tends to be very experienced listeners where SET is an endpoint destination . Again you correctly note the barrier to sucessful adaptation,  simple circuit but high quality parts/implementation are mandatory. The lower quality niche of SET will more likely fail to impress with their poor transformers and power supplies. Finally proper speaker match takes some knowledge and time. It's worth the effort in my opinion. 

Larry I respect Mapman's insights and experiences.  He has found much satisfaction with his class D amplifiers and I sincerely congratulate him.  My exposure and listening to class D experiences are parallel to yours , there's just something missing that leaves me unfulfilled.  As we both recognize these are simply individual impressions,  no doubt that there are many happy users of these efficient amplifiers. I don't question Mapman's  contentment by any means. I know what musically touches me but appreciate we all choose our individual paths. 
Charles, 
Larryi the Class D amps I own and have settled with currently are Bel Canto ref1000m in my main system and C5i integrated in my smaller setup.   Both are simply wonderful devices.  

Id like to add a third system built around either SET or OTL amps but space is limited.  
My experience is similar to Charles. I have Zu Definition 4s (reported to be 101db sensitive) and an Ancient Audio 300b SET. The Def 4s have their own integrated "subwoofer module."   Recently, the tube amp required servicing; and I used a back-up 80 watt SS amp for a few weeks. It was OK, but lifeless compared to the SET. This was most noticeable when I re-inserted the 300b SET tube amp last Thursday. Curiously, I did not have to adjust my usual pre-amp volume setting to "accommodate" for the higher output of the SS amp. I listen to almost everything: classical - both chamber and full-orchestra and chorus, jazz, classical rock, female vocals, etc. It did not matter; everything sounded better with the low-powered SET.
Inna and Charles,  I've experienced some really engaging conversations with fellow audiophiles, discussing everything from the flow of electrons to the flow of notes.  The fun part comes when I tell them I don't own a table.   Suddenly, they look at me as if I have giant lobsters crawling out of my ears.  I do love vinyl, but I don't really like the work and frustration.  I love what vinyl can do so well, but I also like what really good digital can do well.   I have an extensive digital library and really have no desire to go back to vinyl.  That is no more likely than going back to SS amplification having enjoyed a really good 300B SET design.  I think Charles and I are in a good place.  Call us crazy if you want. 
If this shows up as a duplicate post, please ignore. . . 

My experience is similar to Charles. I have 101db efficient Zu Definition 4 speakers driven by an Ancient Audio 300b SET. Recently, the Ancient Audio amp required servicing; and I substituted an 80 watt per channel SS amp for a few weeks. The difference was noticeable, especially when I reinserted the SET tube amp. While listenable, the SS amp was lifeless and lacked tonal depth and immediacy by comparison. One curiosity (and I would be interesting in some opinions); I used the same, midpoint volume control setting on the pre-amp for both the SS and tube amps. The speakers are located at one end of a large (45' long x 16' high) open plan space; and I listen to a wide range or music from classical (chamber to full orchestra and chorus), jazz, classical rock, female vocals, etc. 

Gary
gsm18439,

No doubt an integrated subwoofer or two in play would change the game significantly and offload most of the work (which is always in producing the lower bass frequencies) from the SET. That is a very good way for any owner of a low powered amplifier to go. I would probably consider doing the same if needed. I’ve done it in the past with a mundane 15 watt SS amplifier and solved the problem practically and easily and with  top notch results.
One curiosity (and I would be interesting in some opinions); I used the same, midpoint volume control setting on the pre-amp for both the SS and tube amps.
The volume control setting that would be used is dependent on the gain of the amp (the ratio of voltage out to voltage in), not on the power rating of the amp. In general there tends to be some degree of correlation between amplifier gain and amplifier power capability, but the correlation is a loose one, and the relation between gain and power capability can vary widely among different designs.

The one Ancient Audio 300B amp for which I could find relevant specs is the Silver Grand Mono parallel SET, which is rated at 16 watts and 500 mv sensitivity. For its 8 ohm tap (assuming it has multiple taps) those numbers correspond to a gain of about 27 db, which is right in the ballpark of the gain of many medium powered solid state amplifiers.

Regards,
-- Al


Hi Gary,
The point Iwas attempting to make is what you and larry have noted regarding lower power (including SET) amplifiers. My Symphonic Line SS amplifier was really quite good sounding and I enjoyed it for nearly 3 years. It was powerful, refined, clear and dynamic. I really can not be critical of its performance and service.

Gary and larry alluded to the "lifeless" character of SS relatively speaking. This is precisely what I heard once I got my SET amplifier and Gary you’re right, it’s quite apparent. The tone and timbre took a step upwards, harmonic overtones were more developed and fleshed out. The flow,pace and musical timing were improved. The major overall effect in my system was increased presence,naturalness, vividness, simply more life and emotion.

Brownsfan,
I still enjoy listening to vinyl in other system’s very much, a good friend has a wonderful sounding Basis table and arm with an Aesthetic Phono stage. Yet I find high quality digital front end setups equally engaging. As with you I am not compelled to return to an analog front end. I’m deeply experiencing the musical message with digital these days.
Charles,
The speakers I have lined up for eventual use with a SET or similar tube amp are Triangle Titus XS monitors which are quite small not not particularly extended in the bass but still marginally efficient. They are small but very good for their size and their sweet spot is playing at lower to moderate volumes.

As a result expectation is that a SET or OTL would excel with these perhaps more so than any SS amp. Those using these with tube amps report consistently excellent results. Adding powered subs (most use Class D amplifiers these days by the way)would likely provide what is missing, let the amp do the thing it does best (low distortion when not over driven) and make the system a true top performer.
" harmonic overtones were more developed and fleshed out "

That could be the pleasant 2nd order harmonic distortion Atmasphere pointed out perhaps?

If so who cares really. As long as it sounds good. Nobody ever said accurate reproduction of music always sounds best. Just like there are many ways to enhance a photo to make it look better. HDR on iphone cameras is a good example.  I use it all the time.
Mapman,
I believe you'll be happy with either a SET or OTL amplifier with those speakers.  I'm very familiar with the Atma-Sphere MA-1 and their 60 watt amplifiers.  Regarding SET just be sure to get one with good quality output transformers and well developed power supplies. These are the last areas to compromise if you want top sound quality. 
Charles, 
Charles yes I am with you on that.

The challenge will be space and budget  is limited at first and I will be going only with an integrated amp, not separates.

I am open for suggestions but the white GLOW Amp 1, which I have heard at shows,  is my leading contender at present.   Aesthetics and WAF will matter as well.  It would go into a smaller room and my intent is not to have to play it loud (my other systems cover that).  Adding powered subs may be an option if needed.

I will likely downsize my  home at some point in a few years so options for smaller great sounding systems are of interest.   The Bel Canto C5i is my most recent shot at that and I have been most happy with that unit.
Mapman,
If someone wants to brush off the improved harmonics as 2nd order distortion,  have at it.  My SS amp was drier and flatter in tonality. This fleshed out presentation is much closer to what I hear when listening to live unamplified instruments.  So I'll happily take this increased realism and be appreciative of it 😊😊. We have a family piano and the SET comes closer to its sound, that's good enough for me.
Charles, 
Charles,

Well, based on my understanding from Atmasphere and others, that’s how SETs work. It has nothing to do with semantics.

So that piano you hear is either a result of the amp working optimally and having very low distortion or if it is being stressed at all (not hard to imagine) the introduction of some pleasant sounding second order harmonic distortion.

Also the thing is its impossible for all recordings to sound like any single live piano listening session because each recording is produced differently. Also each live listening session changes based on listening location, close or far for example from the piano.

So if all piano recordings are sounding more like that piano, there is at least a decent chance that is a result of the sound of the system playing the recording, not the recording itself.

In the end it doesn’t matter. All gear does its thing a particular way and different people will take to different sounds for whatever reasons they choose. Its all good in the end.

Another test might be to listen to electronic synthesized piano or other synthesized keyboards that are not necessarily as rich in harmonics as a string instrument like a piano in particular. If I get those extra harmonics that don’t belong there not to mention clipping (even soft clipping) to-boot, that’s a very bad thing for me because the music will sound notning like the real thing done well live. How many electronic music lovers levitate to SETs as opposed to those into mostly Jazz or Classical?

Maybe with a pair of good Class D powered subs though. Then you can probably have the best of both worlds, Class D for the best bass and SET for  mids and high frequencies.

Mapman,

I don't know how easy the Triangle speaker is to drive, but, I do like how it sounds.  It is a nice and lively speaker that has a somewhat "bright" top end that is not harsh or hard or sibilant--a VERY hard trick to pull off and something I find quite appealing.  Maybe not a 45 SET, but certainly there are other candidates that would easily match with the Titus. 

Also, I am not one that is completely wedded to SET amps; I own both SET and pushpull amps and like both types.  If I had to pick a single favorite amp, it probably would be a custom-built OTL that a friend owns that makes almost everything else sound dead in a direct comparison.  I heard it in a direct comparison with an Audio Note Kageki (the SET ajmp I own) and the OTL trounced the SET in the short-term audition of the two.  If I owned a Titus, I would at least be tempted to try an OTL, even though the Titus really doesn't need something extra to bring it to life.

Charles,

I agree with you that digital sources can sound terrific.  If I had to choose digital or analogue, it would be digital because there is MUCH more available digitally than on vinyl or tape.  Most of my listening is from CDs (ripped to a server).  However, while it is not an issue of the inherent capabilities of the medium, there are lots of digital reissues of analogue-sourced music that is quite poor and it is striking how much better an early issue on vinyl sounds compared to the digital reissue.  This might have to do with deterioration of the original tape, but, most often it is indifference in the mastering (evidenced by very good digital reissues of the same music by specialty houses like Mobile Fidelity).  Most jazz digital reissues are quite good, and some classical digital reissues are actually better than the analogue originals (e.g., 1970-80's DG recordings that were poorly mastered for vinyl), but, there is a LOT of reissued pop and rock that is terrible sounding in the digital format.  That is why I have both formats even though most of my listening is from digital sources.

larryi, your assessment of the Titus is spot on!

Technically on paper, I think I would prefer OTL over SET in that the use of a transformer when needed can only hurt and not help most likely.

Problem with OTL for me is all those tubes and the limited choice of speakers for best results.

Also WAF and size though not so much cost.

I decided to try newer amplification technology ie Class D before diving into tube amps and have been quite happy there for a number of years , but of course curiosity still always kills the cat. Thing is though I (and many others including the pro reviewers) have found Class D amps to top performers in most regards already, the technology is not yet fully mature and will only get better. My ref1000m amps are several years old already. The newer ref600m models are said to be even better and knowing the technology that would not surprise me. That Class D still has upside coming down the road as swtiching frequencies and bandwidth continue to improve is another reason I hesitate to make too big an investment in tube amps.
Hello Mapman,
My comments about realistic piano sound was in response to your mentioning 2nd order harmonics vs "accurate reproduction. The SET sounds more like a live piano than other amplifiers I’ve used in my system. I believe it is due to the ability to capture and preserve the nuances and subtle musical cues that are so important. The resonance of the soundboard and vibration of the strings etc. This level of information heightens the sense of presence and the benefit is a more convincing presentation.

It isn’t a case of the SS not sounding good, but rather it couldn’t fool you to the same extent as the SET in presenting believable presence. As a consequence the SET was superior of distinguishing both the players (Monk,Peterson,Ellington or Evans). This also applies to brand differences (Yamaha, Fazioli,Bosendorfer or Steinway). Even less apparent nuances are more clearly contrasted.

This ability to finely discriminate is consistent with all instruments in my listening experiences. I’ve come to realize that perhaps the greatest strength of good SET is its admirable way with the micro,ultra subtle but very necessary details. That it does this in such a natural manner is what’s so impressive. It doesn’t resort to a sterile or analytical character in order to present this beautiful inner detail.

Mapman,
You should give the Atma-Sphere S 30 serious consideration as a lower power and smaller OTL alternative (if you prefer OTL rather than SET).. Surely a good match with your speakers.  Either direction, good luck.
Charles,
Charles, yes Atmasphere s-30 would be nice and I have considered but looking for a more compact integrated amp initially.   Still waiting to see an  Atmasphere OTL integrated amp.  :^).

This would be a third system  in a smaller room if I do it and I am not seeking a large investment to compete with or replace my main system at least initially.    If things work out and I retire to smaller quarters at some point in the not too distant future and decide to downsize, maybe.  It all depends.  We'll see.



Listening to Beethoven’s 7th Symphony with Carlos Kleiber conducting the Vienna Philharmonic. Don’t know if there is any higher order harmonic distortion going on, but it sounds, and feels, like I’m in the hall.

Peaked at 87 on my dB meter.
Tommie,
You're very happy with your amplifier and speakers, I wouldn't change a thing.
Charles,  
I fully agree.
Some reviewers have badly explained the results of low powered sets, and in any case they will not satisfy heavy rock/metal lovers. They just have the greatest purity and enough sound pressure for pleasurable home listening.
My 8watts 300B SET plays on not even horn and not even efficient speakers (marvelous 88dB XTZ Master M2 speakers to hear or have), and yet sounds loud enough. Imagine now with efficient speakers!!! We, family and friends, are continuously marveled by the fabulous tones, dynamics and musicality. Every sound aspect is absolutely close to perfect. It is rare to be continuously satisfied, every time i power it up. Never had this with any of the SS system i had before.
One small advice, when choosing class A low powered SET amps, one must look out for the power supply; there must be a lot of it and of good quality. It is what makes the difference, especially in dynamics and output level.
I don't think it is quite as simple as a great digital system will sound even better with good phono gear added.  I have problems with optimizing my system for one or the other.  I had a setup that sounded quite good with both my CD player and my phono setup.  But, when I went to a music server that has a slightly different tonal balance, if I optimize the sound for the server, the setup doesn't sound as nice as it did before when playing my phono source.  I actually have more flexibility than most people do in changing my sound without taking drastic measures, because I can control the output of both my midrange and tweeter drivers, but, I find it too much of a bother to fiddle with this when switching back and forth.  I actually ended up optimizing the sound for my music server because I listen to it more than I do the phono setup. 
Getting back to the SET subject, I have a Korneff 45 type amp and I am using the Emission Labs Solid Plates with highly modded horn speakers!!! I could not be happier my speakers started life as Klipsch Corner horns but, the only thing Klipsch is the 15" woofers and the original cabinets!!! Everything else has been upgraded, the tweeters are Fostex 90A's the mid horns are 2" wooden tractrix horns with the BMS 2" drivers and a custom made xover using the best parts I could put in them!!! The speakers were rated at 118db but I have them padded down to 108db and the sound awesome!!!
Hi jsman.

I'm interested in learning more about your midrange horn. Is it circular? What are your xo points and what is the horn cutoff frequency? I'm also exploring tractrix midrange horns. Right now with a suitable cone driver but also considering compression drivers.

I can play any music I like at any volume I want included levels that would severely damage hearing. This I can do on 6 SET watts easy. I love heavy metal punk blues jazz classical, pipe organ etc I have no limits this is what one can get with careful matching of amplifier ie SET to loudspeaker. Sure SETs can sound wonderful if used in systems that set a performance limit. But they can do it all if you let them. My SETs are driving 4 -15 inch woofer-2- 50lb compression mids and 2-30lb tweeters. With SET the loudspeaker needs be able to work weak magnets small cabinets complex networks all put limitations on SET amplification.
My 8watts 300B SET plays on not even horn and not even efficient speakers (marvelous 88dB XTZ Master M2 speakers to hear or have), and yet sounds loud enough. Imagine now with efficient speakers!!!
'Sounds loud enough' is exactly the right term but for the wrong reason! The reason it 'sounds' loud enough is due to distortion. If you were to put the very same amp on a horn system, it would not 'sound' as loud until it was actually playing a lot louder, due to the fact that on a horn system there would be less distortion and so it would not 'sound' as loud.

This is because the ear converts distortion into tonality and in addition, uses higher ordered harmonics to calculate sound pressure. If the system has excessive higher ordered harmonics, it will 'sound' louder than it actually is. A sound pressure meter sorts this sort of thing out really quick! If you have excessive distortion, 90 db might 'sound' pretty loud since the ear's sense of sound pressure will be skewed; if the distortion is absent, 100 db (10x louder) might not sound any louder!


I recently swapped out my old EML mesh plate 45s for a new pair of their mesh 2A3s. I decided to go with 2A3s because that's what the ASL Tulip is really designed for. I was concerned that I would lose that 45 "magic", though.

After breaking in, the 2A3s have the magic, along with more "authority". The increase in power is probably 1 watt, or less, but I do get a sense of more headroom, a little more ease on the peaks.

If they really were type 45s, your output power is likely tripled. 45s only make about 0.75 watts or so single-ended. A 2A3 can do 3-5 watts.
Ralph,

I thought 45s made 2W and one should run them at under 1W draw to keep distortion from growing much.

Is this what you mean by 0.75W?

Wow! I thought these EML 2A3 mesh were broken in, but they continue to get better. To me, they Just get out of the way and let the music flow. If you are a fan of the 45 sound, but want a little more power, I'd definitely look into these. They are not cheap, and you may have to wait for a dealer to get them in, but they are totally worth it.

I thought 45s made 2W and one should run them at under 1W draw to keep distortion from growing much.

Is this what you mean by 0.75W?
You can get 2 watts out of them but if you really want to hear what they do its a good idea to run them at a lower voltage (where they will also last longer); in most applications in the old days they were run pretty conservatively. I used to have an old radio that used one and I think it was only good for 0.8 watts or so. But after 70 years in the field it still tested good...
Great thread.  Thanks to all.  I too am using 45s on AN-Es but I can hear the limitations. 
The BIG problem with 45 SET amps is finding the right speaker.  Those that can deliver close to a full range sound at reasonably high volume level and with decent tonal balance are primarily giant horn-loaded systems.  The trade-off is very high price, and having to place a very large system in an appropriate space.  If that trade-off is not feasible, one has to live with volume limitations when using moderately efficient speakers or the tonal quirks of some high-efficiency alternatives like single driver systems.  I have found such systems to be interesting, but, too colored and too restricted in both top and bottom frequency response to be usable with all kinds of music. 

I bring this up because I have, since this thread ended a few years ago, heard some notable exceptions.  The single driver, back-loaded horn systems by Charney Audio are very good all around speakers, capable of playing all sorts of music, and they are quite efficient.  I heard them working with SET 300b amps.  They come with various choices for the single driver.  I particularly liked the one with the AER driver.  For a much lower price point, I like the Rethm Bhaava.  This uses a high efficiency full range driver to cover the upper bass to treble range and has a built-in powered woofer to handle the low end. Like the Charney speakers, these are compact systems that can work in a large variety of rooms.