Myth: low-power high-efficiency

The past 6 - 8 months I have been living with very efficient speakers (~ 109dB/m/w) driven by low-power SET amps. The amps use 300B output tubes for about 7 wpc. On paper, this should be a match made in heaven. In fact, the combination is capable of wonderful nuance, subtley, harmonic richness, and tonality. It is really pleasing, especially on chamber and jazz music. Except for one thing - dynamic energy. I am not referring to loudness. It can deliver more undistorted volume than I care to listen to. I'm referring to immediacy, presence, power, and punch - the life of the music. If you go to the symphony, or live blues, than you know what I am talking about. Next week I'm taking delivery of a 90wpc PP amp, to audition in place of the SET. I need an amp that can maintain the purity of tone and harmonic texture of the SET, while delivering more power, to grab hold and take control the 15" bass driver in my horns.

I searched the archives, but have not found a similar post. Are there any other high-efficiency low-power people who moved to a higher power amp? Are you satisfied now?

Size matters :-)

I came to the exact conclusion you have, and feel the same about the energy and life of music comming from dynamics. I have moved from low power tube amps and horns to high power solid state and dynamic speakers, and it's in the area of dynamics where things improve the most. Horns are supposed to excel at dynamics, but I hear more with the other setup. I never did try any big power with the horns, maybe that would have been a lot more to my liking.
I heard the Druids driven by a Cary 300B integrated and was not prepared for the disappointing sound. On paper and from what I had read this should have been a great match but not to my ears. It sounded lifeless ,no snap, and nowhere near the level of pleasure I get from systems that are not the present darlings of the press.
As you you know from our conversations, I know exactly what you mean. While I love the intimacy conveyed from our 4W SET amp/104dB speaker setup--and will not give that up--when I switch over to the 200W SS amp that we use with the same speakers, there is a presence in the dynamics that comes with the increased power. Our 50W triode amps exhibited the same kind of baseline density and ability to respond to musical transitions that eludes the low watt SET's that I've heard. Still, I think it's all about what you want in a system, or perhaps more about the kind of mood that you're in.

As Terry Cain (of Cain & Cain speakers) says so well:
No one amp will keep a man happy long term. You need a young, firm perhaps not too articulate one you can swing from the ceiling with. And you always need a detailed and refined lower power one, the one you will never ever sell. This amp carves out the essence of tone and artistic intent, but cannot satisfy animal musical behavoir due to power limitation. With music, you cannot have too much fun. Don't let the amps get in the way. If amp -A- is complaining or not keeping up with your musical energy, just grab another and keep swinging.
My experiance has been that you neet to use about 10-15 WPC to speakers with an SS amp to let amplifier open up ("dynamic energy"); whereas an SET only needs .10 that.

Good for a home owner; much less for an apartment dweller with neighbors not having similar tastes in music.
Goodbye 300B!

I have a 300B/Fostex set up as well. At first, I like it but it does not have that "complete" experience. In chamber and small ensemble music, it's gorgeous but I end up wanting more. Dynamics, that is.

Do a survey! From my reading, I found that if you are 40 years old or less, then SET and high efficiency speakers will caught your fancy but eventually, you will move on.
I guess, I have to be over 60 before I fired up my 300B/High Efficiency combo again for good.

I would say that for this particular set up, not only efficiency matters, but the age of the listener itself.
Look at the Mcalister Audio 150PP amp. Look under my threads as I have a full review. I does exactly what you want and need without losing that SET intimacy. I have owned several SET amps and this 75 watt amp from Mcalister is wonderful. Big surprise is it's only $995 new.

Very few know about it. Seems few will take the risk of looking beyond the common names. Only talked with the builder once and I am in no way involved with this line in a business sense.

Just think it is a wonderful amp that others would really enjoy without spending thousands.

Howard, thanks for sharing Terry's thoughts. Although I was a little confused about the subject, audio or life partners. Perhaps his sage advice applies to both!

Ejlif, Eldartford, Lacee and Beavis - thanks for your input. If I understand correctly, your experiences are consistent with mine. I wonder why the myth of High-efficiency and Low-power is perpetuated? Do I assume that advocates of low-power amps are only listening to small-scale music, or that they simply are not extracting the potential of their system?

Amandarae - I like your creative thinking! Never considered the listener's age as a factor here. Since I'm over 40 (although not much), I can only interpret from your post that I'm young at heart :-) And you, too! Thanks for making my day.

Power on, Scott!
I have both SET amps and PUSH/PULL amps. I liked the delicacy of the set amp and midrange magic.No the set did not have the slam or punch off the pp amps they dont have the head room. I have several PUSH/PULL amps and it's all about interfacing. I have a 15 watt, 40 watt, and a 100 wpc. on 4 different horn loaded systems. The 40 wpc. won every time. You want to talk about slam, punch dynamics, it would take your head off. I don't think anything does that better than horns. It can't be just any push/pull, it has to interface. Do a search on web and read these articals by Dr. Harvey "Gizmo" Rosenberg THE SUN RISES IN AMERICA©
SAVING PUSH/PULL FROM ITSELF is an art to build a SET system!Remember, that you have to find the right MATCH of speaker and can be SET,PP, is when the music starts to be "there" with no editorial, just free floating and then you have all...detail dynamics etc. High efficiency speakers is a MUST. SET amplifiers, especially 300b variety...I have had many and all sounded different and maybe a little "300b" same, but what about Final Labs, 47 labs if you want more dynamics?!
I have argued until I am blue in the face that even very high efficiency speakers need lots of power to develop a truely rich sound but that was in reference to my my 104 Db/W/M La Scalas. I think a single driver speaker can sound fairly full with a low powered not flea powered SET amp. I don't consider anything above 5 wpc flea powered. I will repeat my own experience I was raised on K;ipsch Heresies which I bought new in 1977 and powered them with a 60 wpc SS amp which was about all you could get as tubes were way out of fashion for the mainstream buyer. I always wanted the Big Klipsch so a couple of years ago I bought the LaScalas vintage 1978 from a fellow audiogoner using a 2A3 amp to power them. It was a local pick up so I had a chance to audition them. Sure I could play them at loudish volumes with the flea powered amp but the guy was honest and told me that one of the tweeter diaphragms was replaced because in his opinion the power was quote not the right power! I bought them and hooked them up to 100wpc ARC power amp then later a 50wpc Mac and various other reasonable power amps. The result was remarkable the 15 inch woofer came alive and even for what many consier a screechy horn these speakers delivered a rich full sound with bass. I don't know if your speakers are single driver types which really rely on the enclosure to deliver the best bass the driver is capable of. In addition there are watts and there are watts. Some low output amps have fabulous transformers which can somehow compensate for the lack of rated power output, but only to a limited extent in my humble listening experience. In the end I agree Eldartford size really does matter no matter what she says to make you feel better!!!
As Boa2 (or better Terry Cain) so nicely mentioned: Keeping a second amp around for times when you need the additional dynamics seems to be the best idea. My Cain Abbys sound already incredible on 2 Watts for most music: Immediate, lively, engaging, with nice tonal and harmonic rightness. However, to get absolute dynamics and bass control I need a couple of Watts. Of course, this is not too surprising in my setup: I used an 80W amp on a set of 89dB speakers before which would translate into roughly 20W into the 94dB efficient Abbys.

Also, one more comment: Different tube amps can sound quite different and from descriptions the 300b is NOT the most immediate and punchy sounding tube (no personal experience with the 300b though). Did you try any of the other varieties of tubes, e.g. 2A3 or 45? While lower in power they might give you more what you are looking for.

Also, amp-speaker synergy seems way more important with higher efficiency speakers of the horn or single driver variety. E.g. I was quite under whelmed with a pair of Zu Druids on a Cary Rocket 88 or even on a Cary 300b amp as well. Then again, my Abbys sounded much less engaging with a Jolida EL34 based PP than with a 2 Watt Bottlehead amp. Go figure... :) . A First Watt F1 does wonders though in my setup in terms of dynamics and bottom end control.

With best wishes,


I'm in the two amp camp. Wright mono 3.5 set and a Cary SLI-80 PP amp. Both are hooked up to Klipsch speakers. The set amp is marvelous, but does lack some dynamics. The pp amp can pin my ears back but lacks some of the intimatecy of the set.

A suggestion, buy a Niles swiching device and buy a pp amp. switch from one to the other as your mood or music dictates and get the best of both worlds.

I was discussing this subject with someone last week. I made the point that that there are a small handful of SET amps which have that dynamic energy. And where this is derived is in the power supply of the amp. But few SETs have a robust enoough power supply to supply the music with the dynamic energy needed for any large scale performance.
I have had some experience with three amps lately that may have enough dynamic energy to satisfy without having to go without the tonal purity inherent to the SET architecture.
I still plan to see if a 60W PP can approach these in terms of purity. It should be interesting to see how everything measures up.
Different tube amps can sound quite different and from descriptions the 300b is NOT the most immediate and punchy sounding tube.
Rene, the 300B might be a tube you'll want to hear at some point. Aside from its enveloping, holographic nature, this tube in certain amps will drive quite well, and give you considerably deeper and punchier bass than will the 2A3, especially when the amp is SS rectified. Naturally, the synergy between the amp & speakers still reigns, so we must consider this first.

Please excuse the plug here, but for vintage Klipsch owners, these are the ticket to maximizing dynamics should you be running a low-wattage amp. Frankly, nothing has been a bigger upgrade in our system than to go to these crossovers, as they essentially 'lighten the load' on the amps, so now they can drive the speakers with a MUCH, MUCH fuller sound, and far greater dynamic presentation. I suspect that with crossover modifications (or the use of an autoformer), some other low-watt/hi-eff combinations could also improve dramatically. Either that, or bi-amp with a PP or SS on bottom, and a SET amp on top. Hmmmm....yummy!
To my understanding the high-power and high-efficiency isn't a successfull combo.
Higher powered amplifier may deliver a noise that would be non-negligable through high-efficiency speakers.
In search of the "goods" from both approaches, I'm currently using a high powered SET by Bel Canto, the SET40, with a pair of ProAc 2.5s. I realize I won't have the extreme bliss of either approach, but this combo satisfies my "in-betweener" fetish. I also keep around a solid state BAT VK200 for when the urge strikes. Happy, but open to experimentation.

Intriguing development, please keep us informed of what you find. Very curious which PP amp have you decided to go with? I also second the idea of having multiple amps available to drop into the system. I've found that to be one way around the conundrum.
Higher powered amplifier may deliver a noise that would be non-negligable through high-efficiency speakers.
We have a 200W McIntosh SS amp running with 104dB Klipschorns, and even with a tube preamp we get no noise at all. In other words, it works beautifully.

Happy, but open to experimentation.
Are we still talking audio here, Dean?
As someone stated earlier, it may depend on the tube. Try out an 845 tube. Talk about presence, immediacy, punch, life, etc. My Art Audio Carissa Signature is leagues above my prior Conrad Johnson and Cary monoblocks pp's in this regard, and this is with lower efficiency (88db) speakers!
Do you have dedicated power line?
Howard, you know how easily I get sidetracked, heheh.
Do you have dedicated power line?
Nope. We live in a rental.
Hey Scott. I have a speaker rated at 103 db. At least based on experience with my system, a high powered amp was not required to achieve the “dynamic energy” you refer to. I’ve gone from a high powered amp to a small SET amp. The first amp I used was a 160 watt OTL amp. A fantastic amp, but not the best match for my speakers as I was limited to use of 2 or 3 clicks total with my preamp’s volume control. I’ve tried some low powered amps with unsatisfactory results, until I used Art Audio’s PX-25, 6 watt stereo amp with fantastic results. Though, they really shined in the “dynamic energy” department after I inserted the new power cords and cables from Basis Audio. Note, that my subwoofers are powered by an amp driven by the output of the Art Audio; thus your mileage may differ.

I am unfamiliar with your speakers and associated gear. If others that have some of these components can achieve this dynamic energy, then I’d think it is not a component issue, it is a synergy issue. Certainly explore the use of other components with your speakers. But I would not limit this to say looking only at higher powered amps. In fact, like my OTLs, the sensitivity of some higher powered amps may make their use impractical with your speakers. Also, you may want to explore other cables/power cords, etc. I was shocked that changes in these products did significantly more than what I expected, which was a best a slight shift in various sonic attributes.
Aside from its enveloping, holographic nature, this tube in certain amps will drive quite well, and give you considerably deeper and punchier bass than will the 2A3, especially when the amp is SS rectified.

Howard (Boa2), sounds like I got to try a pair of Welborne 300b amps someday :). Of course this is just your fault: You could have sent me the Welborne pair you tried a couple of months ago ;). Actually, why don't you just sent all your equipment north of the border, I always wanted to listen to a pair of KHorns driven by Wrights or a Mac.

Anyway, fun aside, maybe sometime down the line I will be able to listen to some 300b amps. Actually, I already found some Audiophiles here; I just need to convince them to bring over their amp for some extended listening sessions...

Otherwise, I am curious to see how the "switch" to the Mac amp works out for Scott (Skushino).

Best wishes,

Keep in mind not all 300B amps/tubes and high efficiency speakers are created equal.
For amps, the output transformer and tube choice, parts choice and bias can make some difference.
For speakers, driver size to match cabinet design is extremely critical for high efficiency speakers regardless of the efficiency and response rating.

And then there is speaker placement, room acoustics issue.

Can't draw conclusion based on few experiment since some has succeed and some failed.
I've been through this kind of transition in the past couple of years, slowly making a transition to high-efficiency speakers + SET amplification which was fully completed in 2005. I began a few years ago by buying KT88 and 300B single-ended amps to experiment with on a second system set up in a small space. A move allowing me to replan my audio systems from scratch instigated completion of the transition with the purchase of Zu Druids for one system and Zu Definitions for the other. Of course, going to 101db/w/m efficiency simply forced attention back on the amplification.

In a 24' x 12' room, 7/7 watts of 300B power went quite far. And the same was true in another room, 20' x 14' I tried a number of 300B amps and some were quite slow and undynamic, while others were quite lively. My experience has been that there is remarkable variety of sonic signatures in 300B amps. The liveliest 300B amp for me was by Audion. Their circuits all have a characteristic fast, dynamic sound.

However, a single 300B per side didn't have as much ability to project sound into the room and push snap energy into the acoustic space as a single-ended KT88 amp. I had a couple of those, one by Acoustic Masterpiece and another by Audion. The Audion amp had 18/18 watts per channel, by comparison. It had firmer bass than the 300B and more dynamic aliveness to the sound, but didn't have the ultimate focus and intimacy of the 300B.

In a conversation with Sean Casey at Zu, on another topic, he casually mentioned that he really liked the drive of the KR T1610 tube, available in a Cary or KR amp, and second to that he liked the 845 tube. I hadn't heard either up to that point in time, and wasn't really thrilled with the idea of having a tube amp with $1800 power tube replacement costs, so ignored the T-1610 for now. I went looking for an 845 amp and coincidental to my interest found that the last pair of factory Audion Black Shadow 845 monoblocks were available. I bought them. At 25 watts of triode power per amp, I then had the holistic sound of an SET with the muscle of a KT88. This was a quite lively and dynamic sound on Zu Druids.

I went through the same experimentation on the Zu Definitions and ended up with 30 watts per side via a pair of Audiopax 88 monoblocks, which use a dual KT88 circuit that ingeniously models triode behavior from a commodity pentode.

I thought I was settled. And then I began to hear some of the very high end 300B amps, which were at prices that allowed the designers to get more out of the tube. I finally got the dynamic behavior I wanted in a 300B, from a pair of Audion Golden Dream Level 6 parallel single-ended monoblocks, each using a pair of 300Bs for 25 watts per amp.

I was fortunate to have the resources to churn through some auditions in my home to settle my amp/speaker match. I can say that even for a 100+db/w/m speaker, having 25-30 watts on hand sounds like a lot more drive than having 6 or 7, even though the actual SPL the power should drive isn't large. You get more of the sense of reserve and effortlessness that you hear putting something like McIntosh MC1201s on an 88db/w/m mainstream speaker.

I observed a few other things. One is that most 300B amps are change their signature quite noticeably from tube to tube. Various KR 300Bs were dynamic and had a hard attack on transient information, whereas a Full Music or Sophia mesh plate tends to be very smooth. I haven't listened to current production WE 300Bs yet. Some of the very affordable Chinese 300Bs, including the Shuguang solid plates have a lot of snap and sound quite lively, while giving up the lushness that many people buy 300Bs for. Point is, if you have a 300B on efficient speakers, tube rolling has to be part of your strategy for getting the right sound for you.

Also, I had a chance to try a few PX25 amps. At 6/6 watts, the PX25 is distinctly livelier than the 300B, with much less bass bloat. In fact, the PX25 amps had some of the best tube amp bass I've heard from any design. That tube had a very clinical, objective sound, but conveyed less spatial information than a 300B. If I hadn't had the means to look for and find more triode power, I might have settled on a PX25 based solution.

If you're on a budget, don't ignore single-ended pentode/tetrode amps. They solve a lot of problems evident in entry-level 300Bs. For instance, at a local Zu demo held in a 24' x 36' x 16' hotel event room, a little $800 Almarro A205 amp was very impressive with all of 4.8/4.8 watts. That amp has just 3 tubes, with power coming from an EL-84 per channel. While a watt is a watt is a watt, the dynamic behavior of similarly-rated single-ended amps varies considerably by tube and design.

The last thing I did was to try 100w - 500w solid state amps to see whether a dramatic power increase would gain anything useful. What I gave up wasn't worth the small amount of reserve that was gained, however. The same was true trying push-pull tube amps. 25 - 30 watts of SET on a 101db/w/m speaker has plenty of dynamic projection in rooms my size.

Hi Gang, Interesting thread here and many good observations. When one contemplates the many factors involved in the equation here it can be a little overwhelming indeed. I would hazard to guess that the room size would probably dictate ones priorities and perhaps have the biggest influence regarding the power issue. As many here have already pointed out, all watts are not created equal regardless what topolgy we wish to choose....the type of tube employed in set amps,push/pull,triodes, pentodes or SS for that matter. In many cases the quality of the transformers and/or the power supply can have more of an influence than the type of tube employed in the amplifier itself. I am not denying here that power doesn't matter however,if your speakers crossover is a reasonably begign load and the speaker anywhere close to 100 db sensitive, I can assure you that 25 to 50 watts of power is more than enough to simulate the volume levels of a live event in most rooms.... unless of course your room is the size of an auditorium. My main rig is in a huge room....34ft x 27ft with a 16 foot ceiling. I use a pr of Tannoy Westminsters [98 db efficient] and have many amplifiers on hand to pool from.Both high powered tube and solid state as well as both low powered tube and low powered solid state. I can also bi-amp with any number of combinations. SET amps? The wright 2a3's.... nice,clear and vibrant but don't quite cut it full range for anything but chamber music or simple acoustic stuff. When used as the tweeter amp only... more than enough,300b's for tweeter only?.....way more than enough. The 300b set amps [western electric 300b].....a greater sense of the venue,a larger soundstage with more of a holographic presentation,slightly rolled off on both frequency extremes but somewhat soft and lumpy below 100 hz. But what a fabulous midband, incredibly nuanced and fluid though not your rock and roll amp for full tilt boogie. Higher powered 845 based set amps bring a whole higher dynamic presentation to the table. The cary 805 will rock with the best of them,and will handle any and all musical genre at any sane volume level one chooses to listen at,and does so without any hint of compression,glare or collapsing of the stage...although it possess decent bass power and weight, it's still somewhat soft and overly ripe in the bottom two octaves. By contrast, the Antique Sound Labs parrallel 845's 60 watt 1009 monos have a similiar presentation,seemingly unlimited dynamic range with a far superior bass range akin to the better high powered push/pull tube amps like the el-34 based VAC pa-90's,the kt-88 based mfa 120's or the Jadis Defy 7 and as good as any tube amp I've had the pleasure of listening to in my room.When compared with high powered solid state.... The Bryston 4bst just flat out boogies at any volume levels with recorded rock n roll music.As does the Krell KSA 50,classe dr3 or the little bedini 25/25. Bass energy and power that is second to none, a percussive vibe that most tube amps only hint at. Funny thing here is: [to my ear anyway] I much preferr the sound of the lower powered [high current] classe A ss amps to the higher powered solid state stuff, at least when powering the Tannoys. They seem to be a little more articulate in the bottom octaves as well as possessing a sweeter sounding treble with less of a grain structure in the midrange.Any one of the SS amps above will play to well above 100 db in my room without any sign of dynamic compression or diminished dynamic range. At times: when I have a room full of people over for social gatherings [read party here]sometimes things can get a little carried away with regards to SPL's. Yup... 50 watts is way more than enough in my room.Just recently had a pre Christmas gathering with around 30 people over.Many of them are professional musicians that stop by regularly to jam. A friend had been restoring a pair of old vintage 30 watt Eico monoblocks . These are a parrallel push/ pull design from 1959 that employ the el-84 output tubes.The circuit was stock,original transformers but obviously tweeked and updated with modern coupling caps as well as power supplies. WOWZA!!!! These babies just flat out rocked the room and with a bass punch that knocked me out. They simply made music believable and in a room full of people no less.Hey, I think I'm getting a little carried away here but: Big has it's own vibe I suppose,different stokes for different folks.
Hi Scott, after trying many amps over the last year (including 45&300b SET) on Westminster royal HE(99db). I also prefer a bit more power for many of the reasons stated by others.
I am really enjoying Nagra VPA's 845 push/pull, also still use McIntosh 2102.
Happy new year!!
Sonus Faber Stradivari and Nagra 845 is a fine match that I am fortunate to hear at the home of a friend of mine.No lack of dynamics, bass depth that goes thru the floor, and great detail even at low listening levels. Need I mention that there is no listening fatigue?When this fellow hosts listening nite,we always stay longer.
for anyone who loves rock or classical music(orchestra), set's simply don't cut it with any loudspeaker. once the rock era began, they were obsolete. there is no denying they have a charming sound, but very limited appeal. except for a few audiophiles who love the most simple acoustic music, they are nothing more than a cash cow for manufacturers.
The best option I can come up with is something like the new Jordan JXR6 HD 2" driver which goes to 80hz and useful bass into the 60's. Maybe put two drivers in each cabinet. This is good for vocals etc. Fostex is anothere option for higher efficiency.
Combine this with self powered 15" stereo woofers which kick in with dynamic bass heavy music.
No SETs were not made to listen to rock, if that's your thing get ss or pp tubes. But on jazz, chamber music, female or male vocal, they ROCK.

There's really no problem listening to rock or full-orchestra classical music on SETs if you have enough speaker efficiency and the impedance is reasonably consistent. A good SET amp using an 845 output tube on a 100+db/w/m speaker will rock as well as a push/pull, and have better definition too. And you can get good-rocking 300B amps in the upper price ranges. On the other hand, a 45 tube SET with just a couple of watts might rock better than one would think but there are better alternatives.

I agree, a fascinating thread and a subject I have been struggling with. I discussed the power issue with Kevin Scott here in the UK, he makes the well regarded Living Voice Speakers, a range built with tubes in mind and with about 94db sensitivity. I was contemplating the Welborne lab monoblocks and Kevin said, they would be great, but limited to small scale music, Jazz combos, solo singers. It is not simply a question of rock, large scale Classical and opera chorus's put similar demands on a systems abilty to cope with dynamic swings.
The conclusion, 7 watts good, 18 to 22 watts of SET power much better. I also concur with looking at 45/845 tubes rather than 300B's, for the frequency extremes. The problem of course, is that good 20watt SET's with adequate transformers, aint cheap. I was lucky to find an ex dem Viva Solista from the audio pimp on the Gon(strongly recommended by the way) for "only"! $3500 new its $9000. It is an 18watt 845 SET and I am pefectly happy, real drive and dynamics, even on compex congested passages. Unfortunately I had to go for a Lavardin IT integrated for warm weather use, equally wonderful, but quite different.
Those 2 amps will keep me happy for the forseeable future. The next temptation is the new range of high sensitivity compression horn speakers Tyler Acoustics is bringing out. When will it all end?