Sonic qualities of SET output tubes?

Can you readily identify a 300B, 2A3, 805, 211, etc., amp’s sound with your eyes closed most of the time?

If so, I’sure would like to hear from you.

Amplifier design and the technology utilized within its confines decides the ‘voice’ or influence it will yield as much or more so than merely the output tubes the designer has chosen to use.

I get that part emphatically. One must hear the amp regardless the type of output tube technology on hand.

And yes, some Pentodes and Tetrodes are used as Triodes but are not indeed triodes by their specific architecture. That’s OK, just focus on their use as Triodes herein, please.

There are however certain tube types, irrespective of vintage which have basic undeniable sonic colors or characteristics, apart from their electrical aspects which keep attracting people to amps which use this or that tube in its output stage.

Some love 211s. some adore 300Bs. Some love EL34s configured to run as Triodes. I have an affinity for the latter. So far anyway. This topic could change my mind.

Has your own experience informed you what this or that output tube’s natural flavor regularly announces itself to be so you can have a reasonable expectation of its general presentation?

What sonic attribute continually attracts you to a particular SET tube design, 300B or some others?

Or, conversely, what is it about the sound that would bring you to covet a 211 amp over a 2A3, for example.

Why as another example, would you pick a 2A3 amp over one using 805s or 300B, 211, etc. or vice versa?

Removing ‘vintages’ and electronic or electrical qualities from the argument, what sonic attributes for the more popular S.E.T. amp output tubes have you determined seem to persist in their particular DNA?

I’m asking for input from those SET tube devotees to lend their experiences and knowledge on the subject of what tube sounds like what irrespective of the SET application, generally speaking.

My goal is to try getting a better feel for which SET Tube amp design, if any, I’d want to pursue and possibly invest heavily into going forward as the soul of a new system.

Tremendous thanks to all!

The difference between tubes themselves is not that profound. They are just tubes and they have very similar linearity and bandwidth.

This is not true of output transformers!  Here's the problem- the more power there is, the harder it is to get bandwidth out of the transformer (and in this regard, much moreso than is encountered with push-pull; we sidestepped the whole thing by eliminating the transformer altogether).

So as the output power goes down, the sound of the amp improves. 25 years ago the 211 was king, 20 years ago the 300b was king, by sometime in the early 2000s the 2A3 was king, now we're seeing the type 45, 10 and 71 vying for the title. A traditional 45 is good for about 0.75 watts.

Now as transformer designs have improved (some taking advantage of technology not available in the 1920s and 1930s) its been possible to extend bandwidth in higher power designs. So the result is you're going to get a lot of conflicting anecdotal comments.

The other issue I've not mentioned is how well the tube and the output transformer work together. Some tubes want a 5K load and some output transformers present 4.9K or 5.1 K instead of exactly 5K (which will vary from tube to tube...) so you're going to see variance on that account as well.

So don't expect consistency in the comments to follow.
I really can't add much more because atmasphere has covered all related details very well and is spot on.

The only thing you may think about is the correct pairing of a lwr pwr set Amp in your system and have reasonable expectations.

I tended to like the 2a3 the best in the right system but my current setup requires more pwr and isn't a good choice now.

You might list the rest of your system,room size,average volume level and types of music you generally listen to.

Ralph, Thank you for this great post. I enjoy your posts as they are always so informative.  

Atmosphere > as the power goes down the sound improves.

Blindjim > Atmosphere thanks so very much Lemme see If I am getting this correctly.

Many or all of the output tubes predominately used in SET amps more or less, possess about the same electrical criteria, bandwidth,linearity, so the apparent sound or voice we hear from various Triode amps output tubes comes mainly . as the result of how well or badly they match up with the transformer being used, and how much they are being pressed to output power?

I will suspect too, the limitations of pouwer output makes their transformers either larger or smaller by comparison to other Triode output tubes.

Lower power = Better sound.

OK. Period paragraph?

I know the A’gon bottom line here… “ya gotta try it or them to really know”. Fine. I’m merely looking for directions now, not whose name gets put on the check or to whom I hand the plastic.

PP amps are certainly an option for me.
Here’s my inference….
Every pre or amp (s) I’ve owned was a transformer coupled arrangement.
In previously owned multi tube line stage fully balanced preamp, and one entirely SE, switching in and out the same tube type, but from a different era or from another Brand, always changed the sound.

Sometimes the performance being realized was improved too, not always though. At times, the gains were marginal, sometimes though, immense. Those earmarks were more silky, more or less smoother, more bottom end, more or less dynamic, more or less perceived extension.

It was either that or I’m deaf as well as nuts.

I swapped out 6922s to other brand 6922s and the sonics were altered. I switched out 6922s for 7308s (an electrically appropriate replacement tube) and the change was not subtle. Only the era of the tubes were different, otherwise, they were the same maker, Amperex.

In that same preamp I replaced RCA or Phillips ? 6L6 with Tungsol 5881s and again, there was improvement in several areas.

In the SE preamp merely replacing the 12AT7s and 12AX7s from JJs to RCAs to Amperex Bugle Boys, realized an increase in performance each instance, respectively. The Amperex BBs unquestionably were the top choice for overall performance increase.

Once more in a pair of mono blocks using EL34s in Ultralinear, moving out the JJs to CED Winged Cs made me a much happier camper.

Even when an amp was running in Ultralinear I preferred the EL34 to a KT 88 amp of similar output and expense.
Along the way, I have seen thru various brands and iterations, each tube model had a specific or IMO indemic fingerprint on the sound and its presentation albeit to lesser or greater degrees. Always however, the flavor of the sound became altered with the rolling in and out of even likewise tubes.

Other tubes came and went I simply do not recall them all, but my rationale for posting this question or inquiry for feedback on Output tube ‘Flavors’ was the direct result of those experiences.

Enjoying the sound of ‘glass’ from my experiences a good bit more than what I’ve heard from completely SS powered affairs, I’m nearing the cross road of making the choice to go this way or that with a projected system build. Tube power, tube and SS power, or simply go all in and use tubes for control and power on limited funding so only one option is possible.

… and we’re back to the original Q… which 6550, 300B, EL34, KT88, 211, etc., is it going to be?

As such, and it seems tubes have the present vote, then Which tube preamp would be a likely prospect for me with my musical preffs which range greatly?

I can only surmise, it will likely be PP, not single tube power amp.

Kenny. > more of your setup info is needed.
Blindjim > I’ll be needing speakers and amp (s). other items too for sure, but mainly those two items to begin.

Medium sized room (14W x 20L X 9H) closed off completely. This will certainly change to a somewhat larger overall room too. I’d opt in for one a bit wider to 16 or 17ft, and about the same for depth, 20 – 23ft. or so.

Listen to everything but Rap, Hip Hop, and what is being called present day R&B, but I do like old school RB. Not big on show tunes, opera or classical just now, but I do enjoy some. Defaults are CW, Folk, Americana, Blues, RB, Classic Rock, some POP. Not keen on curren themes on many of the standard genres. Even country ain’t country any longer. Love bluegrass. Singer songwriters like Simon, Morrison, Chapman, Baez, Prine, Zimmerman, Stapleton, EJ, Cash, Yokam, etc. Jazz, Reggae, and solid Rock bands such as AC/DC, Def, Zepplin, Airplane, Santana, and so on. Big bands doing jazz and R&B, and Rock. And others.

Speakers are as well another Question mark if a tube amp does get elected. Otherwise, I’ve a short list for those speakers I’d think a solid choice, all of which appear to need or enjoy significant power and or ‘damping.

All of them will be off the table if I opt for another tube amp or amps.

A great concern is acquiring a ‘too lush’ sounding triode amp or amps that are counterintuitive to the genres I dig. And, or being forced into buying horns for this or that amp and then being sentenced to life with the pairing or taking an enormous loss on a later sale of either or.

If you are asking about SET amps, I don't think the question of speakers is a secondary one. I've heard speakers that can play with SET amps but aren't really sustained by them and benefit from greater power. I think you have to treat the amp-speaker combination synergistically. Don't mean to sound patronizing, I gather you have been around the block. 
I'm listening to two very different systems right now- a horn system with Lamm SET amps and a Quad ESL with old Quad II amps and top notch glass. Both are marvelous, but the amps are working well within their parameters and mate extremely well to the specific speakers. 
Whart is spot on. The sensitivity of the speaker is vitally important and that must be known before picking or considering any amp. For example, a speaker with 89db sensitivity at 8 ohms will require far more power than a speaker with 98db sensitivity at 8 ohms. The first speaker will need at least some 50 watts,  while the second will work with perhaps 3-8 watts.

As the sensitivity goes down the need for more power goes up significantly. I know you are aware of this due to your seniority and experience here.

Knowing how loud you play your music and the type of music played are also important considerations. Can a 30 watt tube drive a 89db sensitive speaker to 75 -78 db comfortably in a modest sized room? Yes most likely. But if you want db levels approaching 90db on average on some listening sessions with orchestral scores, then absolutely not.

I have read some great stuff that Ralph at Atma-sphere puts out on the watts and db relationship with tube amps and speaker sensitivity. Perhaps he can repost that here.
Post removed 
At the risk of redundancy I must agree with Whart and his sage advice regarding amplifier and speaker matching, a critical point. This is especially true for lower and mid powered tube amplifiers, you have to consider your options simultaneously.

I have three tube amplifiers.
100 watt 6550/KT 88 push pull
40 watts el 34 push pull
8 watt 300b SET

The 8 watt has superior sound quality driving the same speaker as my other two amplifiers. This possible due to the choice of the speakers I use. I suspect that you’d be very pleased with a moderately powered class A tube push pull, Jadis for an example or the VAC Renaissance 30/30 (300b push pull) with an easy load speaker with sufficient sensitivity. SETs aren’t for everyone although they’ve served me extraordinarily well.

I can relate to just about everything you have said,

I may listen to a little bit different music than you do and have a slightly bigger room,20x25x9 that opens into our kitchen.

I have put a lot of effort in matching the right components to get the best sound for me overall.

I have Tekton double Impact speakers that are 95db with 1 watt,and they have a relatively flat impedance load so they are easy to drive.

I have the linear tube audio MZ2S preamp which can be used as a headphone amp and also can drive speakers with a 1.38 watt output into 4 ohms.

I have tried quite a few different amps with these speakers and I like the Linear tube audio Zotl 40 with both products using all nos glass.


Whart > If you are asking about SET amps, I don't think the question of speakers is a secondary one.

Blindjim > Thank you. you are indeed correct on the synergy factor. I’m in the assimilating information role currently on both ends of this enigma. , er, project.

Speakers are IMO way more sexy and impossible to ignore in a room. I feel too, they are the only items one should see or hear as the electrical gear needs be sequestered into an adjacent room or space as is my present circumstance.

BTW… which Horns?

Grannyring > The sensitivity of the speaker is vitally important

Blindjim > Thanks Grannyring. Very grateful for the affirmation. Got it.

It works the other way ‘round too. In fact, once I quit being stubborn and dive into the tube amp (s) path, speaker types and their attributes will be forced into renegotiation. I suspect then, both amp and speakers will be bought or ordered in simultaneously, each with the other well in mind.

RE driving to concert levels.
This is hardly an issue for me sure I’ll kick things up to an average of in room db levels to 94 or 95db…. For one song, maybe two. That’s all. Perhaps a few songs will get some more watts beyond avg. levels, but I’ve noticed with the loss of vision and some maturity, I’m no longer attracted to loudness for the sake of loudness alone.

it actually hurts.

Usual listening levels are just above being able to casually talk to someone else in the room, requiring the sound be turned down or muted to do so. So somewhere in the mid 80s maybe. Never bothered to test it when I had the chance or did and then forgot...

Which ever match up gets the nod, it will be more than capable of handling these isolated events.

I’m nuts, not insane and I would sort of like to keep the hearing I still possess in tact. In fact, if I’m at a location and the levels are tremendous I’ll probably leave regardless how much I might love the performers. Ordinarily I’m only going to outdoor shows, in the evenings or from Nov to Apr., when possible.

Lengthy streams of screaming wailing instruments and singers have slipped into the ether leaving me fondly and forever behind their wake. They are but intermittent blasts from the pasts these days.


Can you readily identify a 300B, 2A3, 805, 211, etc., amp’s sound with your eyes closed most of the time?

You asked this main question and I thought I could give you my opinion on this.

I believe to some small degree,along as each individual different output tube has the proper circuit design and the amp has the correct matching between tube and transformer,the 3 most common lwr pwr tubes,300b,45,2a3 have slightly different sound to my ears and that comes from listening and or owning a few but certainly not all designs.

300b,has the most midrange warmth and body with slight extension roll off on sides of the frequency range.

45 tube has more clarity with less midrange warmth and body,but has greater frequency extension.

2a3 tube to my ears splits the difference between the first two.

Similar sonics to all 3, 
They will have a certain purity and inner glow that also some people refer to as "breath of life qualities"that no other topology of amps tubes or SS have,at least I haven't heard any in 35 yrs.

The big pwr transmitter tubes that I've heard or owned generally sound quite similar with not very noticeable difference in sonics.
 But Offcourse the same as the lwr pwr amps there is just to many variables in the overall designs to really speak accurately to the differing sonics.

Atmasphere provided a great list of variables in design that most certainly effect the sound.

Other Variables that can effect the sound in all tube amps,

Power supply
Type of output transformers 
Types of coupling capacitors 
Different brands of tubes
Different types of driver tubes
Different types of rectifier tubes
Hard wired or circuit board
Solid state or tubed rectified 

And probably other things I'm just not aware of.

I only own one set tube amp which is a Yamamoto A09s which is a 300b 8 watt per channel amp.It's a slightly different design than most 300b amps.It uses Torroidal type transformers in the pwr supply and also the output transformers which gives a slightly different sound.

Way to many variables overall to accurately predict the sound and the best way is always listen to one in your own system and room.

Hopefully I helped you,
@blindjim - the horns are Avantgarde Duos which I have since around 2006- so they aren't one of the newer models but benefitted from some of the running updates prior to the Omega modification. Their internal woofer system is augmented with a pair of 15" subs that crossover very low- e.g. 50hz on a step- 24db/octave slope. With some adjustments to volume and phase (and a little DSP box only on the subs), they give some additional heft and dimension to the Avantgardes without distracting from their coherence. Even that speaker, with its 104 db efficiency, can benefit from a more powerful amp, but there is a synergy with the Lamm ML2, which I like very much. It's instructive to listen to them against the Quad ESL--the Quads are so compromised in certain respects, but their vital strength--the midrange--overcomes most of their shortcomings. 
Most music is in the midrange and to hear it all clearly as was recorded you need full or near full range speakers. Unless you only listen to violin solo perhaps. You also need powerful, life like dynamics. Lamm's SET watts are said to be the most powerful SET watts anywhere, they will drive some dynamic speakers well - you wouldn't have to consider horns only. Give them a listen if you can, if you do and like them a lot - don't call me and Bill names, OK? They are expensive, even used. Vladimir Lamm is good to deal with.
Anyway, you probably need a list of a dozen or so amps to audition. Of course, it's an amp/speakers unit, but still - do you prefer to do speakers first or amp first approach? I myself at this level would try both, in the end I would find the right sound. 
I thought I would just mention tube and hybrid amps that I would want to audition first: LAMM, Ypsilon, VAC, Atma-Sphere, Wavac, Allnic, Jadis, Octave, CAT. Ralph is right - pay attention to the sound not the design. You really need to know what kind of sound you are looking for and the compromises you are prepared to take, and if you already know that - it's both easier and more difficult.
But give horns a listen too if you can unless they are out of the question. In addition to Avant-Garde I would listen to Acapella.
As I said in another thread, $35k for the entire set-up including cables is tough. Yes, I understand you might consider spending more if you see that it's worth it. Some people save $500 on cables after spending $25k on equipment, not wise.
You can tell that this is a great sound, though the base probably doesn't go too low and that it lacks the ultimate authority of much bigger systems. But for a normal medium size rooms it should be just about perfect. However, it's analog source and an excellent one.

charles1dad > you have to consider your options simultaneously.

Blindjim > Appreciate it greatly Charles. Somehow A’gon slipped my post out of order, or your post got up too late. Anyhow, yep. Agreed. See above on the ‘simulcast’ episode..

charles1dad > I suspect that you’d be very pleased with a moderately powered class A push pull tube

blindjim > Mebbe so. Somehow I’ve fallen in lust with some speakers that simply don’t love tubes for whatever reason. Oh, they say they are OK with tubes, but their IMP drops say differently… so do their owners and reviewers.

Life seems so much more simple when all that is needed is to lay two very nice 400 – 500 wpc monos in between a pair of upper range speakers, kick back and dig the tunes… which is my default plug and play system choice.
Never go into the big room!!!

kdude66 > I can relate to just about everything you have said,

Blindjim > sorry to hear it. So, how many shrinks do you see each week? All of mine quit.

kdude66 > I have Tekton double Impact speakers and Linear tube audio Zotl 40

blindjim > You are the second person to mention those two items to me this week. Are you involved in any conspiratorial activities lately? lol
Is the Linear tube a Dave Berning design?

where can anyone hear these two items together or at all?

kdude66 > ,300b,45,2a3 have slightly different sound to my ears
“…. big pwr transmitter tubes that I've heard or owned generally sound quite similar with not very noticeable difference in sonics.”

blindjim > huge thanks for the insightful input. I tend to agree, right or wrong on the near audible sameness of higher output tube amps.

Whart - the horns are Avantgarde Duos which I have since around 2006

Blindjim > thank you. I don’t doubt for a minute that pair is very nice.

Inna > think about these…

Blindjim > thanks so much. Input like yours has been invaluable.

Despite my affinity for tubes, so far, only in Ultralinear with modest high eff speakers, one fact remains constant. What ever the amp is, IT MUST BE AUTO BIASING.
I can no longer bias amps, nor do I really want to.

Its been obvious to me for a bit now I’m going to have to go where a lot of gear is available to see and hear. The more, the better. A show seems in order.

There are a couple venues in my area that I am aware of which carry good inventories, albeit, not sure what would be ready to hear at any given moment. Or, if anything there would be of considerable interest. Although, I’m gonna stay as open minded this time as is possible.

I’ve read tons of stuff on INT amps both tube and SS. Gryphon and Ayon appear to have an awful lot going for them in the 300 & Triton III, respectively. Only the latter amp applies here.

I’ve read so much it is confusing now.

These past few posts have been revealing. I’m deeply grateful for them all.

Physical style or build is not much of an issue for me. As long as it doesn’t look run over by a train or herd of migrating Guinea Pigs, all will be well.

Ralph uncovered the point I’ve been missing for a very long time…. The lesser the power, the better the sound. Sure seems like it to me.

One item no one mentioned yet is noise. Ultra high eff speakers amplify noise too. Keeping the power line and ancillary electronics noise quiet is another matter that can crop up or needs be addressed when in those scenarios.

Its akin in my opinion to the noises generated by turn table playback systems by the record itself.

They ain’t all perfectly silent apart from the recording itself!!

For me, this is going to take some re-thinking. Perhaps SET ownership for me ought to be on a lesser scale as a secondary system. That would be pretty do able. Two ways on a lower budget, and maybe a 300B or EL34, all in a much smaller room like an office.

Done on a much smaller scale, avoiding PP amps would be much easier.
I had planned on a smaller secondary rig anyhow.

We’ll see.


You are the second person to mention those two items to me this week. Are you involved in any conspiratorial activities lately? lol
Is the Linear tube a Dave Berning design?

Yes it's supposed to be a secret but we are looking for more members

All the Linear tube audio gear is greatly influenced by David Berning and has his blessings Offcourse.

I don't know where a guy could listen to the same gear I have but I've been told that Linear tube audio is getting a set of the Tekton Electron speakers to demo their amps with in their showroom.

I went to a shrink many yrs ago and I was told that I'm a hopeless case and they really aren't qualified to help me.😃

Best set of luck to you in your search,

You would do me and us all a favour if you listened to Ypsilon before buying anything. By many accounts, including Michael Fremer's, it is one of the finest brands available. Yes, their 100 wt/ch integrated is $25k new. And Gryphon Diablo 300 is another one to hear. Both designers are highly respected. 

those low-powered amps sound good in completely empty room and speakers firmly attached to corners so you can hear somethin'.

@blindjim , all the comments regarding speaker efficiency are spot on.

And you are quite correct that different brands of power tubes are going to sound different. Once you settle on a particular power tube type, then you sort out which brand of that tube to get. The choice of power tube type is heavily dependent on which speaker you get!!

The one thing you want to pay attention to is the way SETs make distortion. In that regard, they are very very good at low power; distortion falls to the point of being unmeasurable (which is the source of the ’amazing inner detail’ for which so many SETs are known; the amps we make are some of the very few push-pull amps that share this low power lack of distortion character). But at full power, the typical distortion is in the neighborhood of 10%.

SETs are known for being quite lush and very dynamic. Both of these properties are due to distortion- the 2nd harmonic brings the lushness, and at powers over about 20% of full power, the upper harmonics cause the dynamic properties on account of the way the human ear perceives sound pressure.

You really want to avoid the higher ordered harmonics! Not only do they cause the amp to sound dynamic, but they will also cause the system to sound loud and shouty. You will see a lot of people talk about the fact that their system plays as loud as they want; this is **often** caused by the distortion and not the actual sound pressure. A good system should **never** sound loud!

To avoid this, the speaker simply has to have the efficiency such that you don’t exceed about 20% of full power of the amp you have in mind. This will have the amp playing its most transparent and with its smoothest qualities. Generally speaking, this means that in most cases, a speaker of less than 100db is not going to be suitable. I am full aware that there will be many that read this and will dispute these words; my recommendation is to reread this post! For these people, if your system is not set up by this rule of thumb, you really aren’t hearing the finer qualities of your amp, no matter how enjoyable it might be.

Wow just Wow,
Incredibly well written and explained priceless information IMO.

Thank You,

A couple of months ago I bought a Dennis Had Inspire SE "Fire Bottle" HO (high output) pentode based amp of recent vintage, and have been rolling various tubes through it…note that this sort of amp has only 4 tubes so rolling is el-cheapo. So far I've noticed differences between rectifiers…234B, GZ34, and a 5Y3S…interesting…more bass, less bass, soundstage changes, etc., and output tubes including KT88, KT77, KT150, 6550, and parts of an old toaster (not really, but uh…). The amp came with a NOS Amperex 6SN7GTB, and I tried another of the same type of Amperex of a different design (getters on the side or top or something) and those sounded identical. Everything seems to change a little or more than a little, and all of it is fun. Note this amp has lots of dynamic juice in its massive 12 watts per side, sounds better than any amp I've owned in over 5 decades of gear silliness, and proves once again that "everything I know is wrong." 
+1 Atmasphere. Great post. I know first hand that distortion always sounds louder and at first can even sound impressive when too few tube watts are trying to drive the wrong speaker too loudly.

Well said and very important learning for us all. Helps us pick the right amp/speaker combo based on one's goals and listening habits with a system.
Ralph, there is usually a lot of distortion in the recording already. How do you try to correct that? Or you simply live with it and do your best not to make it worse?
Artificially lush and shouty sound is something that I realy hate.
@wolf_garcia     Please  remind me of the speakers you are now using. Thanks.
there is usually a lot of distortion in the recording already. How do you try to correct that? Or you simply live with it and do your best not to make it worse?
There may or may not depending entirely on the recording.

You certainly don't want to **add** to it! So yes, you do your best not to make it worse.
So I thought. Those recording engineers from seventies, what did they think they were doing? Best jazzrock albums, starting with Bitches Brew, were very poorly recorded and probably mastered too. Japanese pro records are the best but still so much distortion. Pink Floyd is not particularly good either.

kdude66 > All the Linear tube audio gear is greatly influenced by David Berning and has his blessings Offcourse.

Blindjim > ROTFLMAO 8-)….. THANKS. VERY COOL, Where is LTA home base?

Inna > Please listen to Ypsilon; Gryphon Diablo and the 300.

Blindjim > thanks. I went and read the Fremer article after much trouble to do so. Liked what was said about the really expensive amp he had some primary input tube or bias issues. There are a couple really valid concerns for me with the mentioned amps herein.

Barring it’s a bit off topic, First, is money. Second is value in the secondary market. Yes. These are reputedly ‘destination’ ish items. But I’ve been around long enough to know I need to be around a lot longer, and very few presupposed ‘keeper’ anythings seldom become exactly that.

Lastly, its getting to hear any of them in any suitable setup without contracting guides, bearers and a Shaman to get there.

Atmosphere > Once you settle on a particular power tube type, then you sort out which brand of that tube to get. The choice of power tube type is heavily dependent on which speaker you get!! …or want.

A good system should **never** sound loud!

the speaker simply has to have the efficiency such that you don’t exceed about 20% of full power of the amp you have in mind.

Blindjim > Much respect and immense gratitude for the knowledge. Truly.

However…. Perhaps it was the choice of words used. Not sure. Maybe this is theoretical only.

Employing the philosophy that an amp should not or perhaps never, exceed 20% of its rated output to adequately propel the speakers SPL to satisfying levels gives me great pause.

In a perfect world? This means your 60wpc monos are actually 12wpc monos if applied correctly??

Superficially, it should give many audiophiles great pause now, or going forward an entire resetteling of standard system building notions and themes in tact presently, and from years back. Well, from the ‘90s anyhow are suddenly unceremoniously banished forthwith.

Under your inference, we should now consider the new shiny expensive 100wpc amp is only a thoughtfully applied 20wpc amp is gonna be a real tuff pill to swallow. It’ll break a lot of hearts. Not to mention wallets as folks begin scrambling for new larger amps, or easier to run speakers. Or both.

Still more pointedly, the overwhelming majority of loudspeaker makers should be shivering in fear of such a notice for amenable amp & speaker combos has abruptly evaporated until they redesign things so their 83 to 92db units get with Jenny Craig and reduce their dudgeon dwelling impedance curves to slimmer sleaker heights, whiole at the same time increasing sensitivities into triple digits.

20% of rated power. Whoa! That’s a pretty strong edict. But OK. I’m probably missing something important.

Lastly, that good sounding rig ought never sound loud really jiggles my jelly. “…. Hath sounds to soothe the savage beast”.

Now there is a decided dissimilarity between a speaker playing loudly and a speaker ‘shouting’.if that was the actual meaning in your remarks on what a rig should never sound like.

Occasionally, them thar “soothing” sounds are loud ones. Albeit here, everything is subjectively accounted. Although in room SPLs averaging more than 90db simply must be considered loud as an example. Practically speaking much less very likely.

I’ve gotta have a stereo that provides soft, normaland loud sound, or yields a substantial degree of variance in SPLs.

I want more than a quarter inch of spin on the volume knob to go from low to OMG!

IMHO, my home audio rig is NOT doubling as a PA system or a back up for the local sports stadiums. Yeah. I doubt they’re using enormous amounts of watts there either. Just horns.

300Bs = 2 wpc and then stop!! Wow.

What am I missing?

Looks like I need to revisit Google for the graph on watts and DBs and SPLs.

I’m not going to sleep well tonight. Maybe ever again.

wolf_garcia > rolling tubes …. …. I've noticed differences between rectifiers…234B, GZ34, and a 5Y3S…. and output tubes including KT88, KT77, KT150, 6550, and parts of an old toaster

blindjim > hahaha…. lovely. 2 slicer or 4.
Its great to have amps like that one. I always get the ones that cost so much to roll with it becomes a scary prospect to do so. One can only give so much blood each week darn it.

On distortion in recordings
A fella who told me he was a studio musician back in the 60s said ‘at times’ a more than good bit of the music was mixed for playback on automotive dashboard speakers. Plain old car speakers sitting in as monitors. Why? Because that’s where 90% of the music was going to be played.

The first thing I did in my old Chevy was to throw in a pair of Jensen 6x9s, and a Craig Power play FM & 8 track 20wpc deck. Smoking loud rig.

The more often I recall this conversation the more I think there was more to it than why much of the pop and rock and RB songs were so poorly recorded well into the early ‘90s, and beyond.

I’d guess it was lable concentric, and or artist predominate. Better lables and more popular artists recordings I’ve heard even today, sound better than those of the ‘rest of the herd” even off the same lable. Some labels don’t have as great a disparity across their artists, but the big guys do seem to get the better engineers and studios… until they buy their own houses.

Many acoustic recordings going back a long ways still sound pretty good. Electric powered instruments have had a tuff row to hoe for decades.

Thank God for mobile devices and PC desktop rigs. That’s where its more about content than fidelity. Play the bad stuff there.

Apple is still missing the boat in lieu of the onslaught of HD and lossless music and the resurgence of new or even other formats apart from Apple’s proprietary formats… and they will continue to do so until their base quits buying compressed tunes thru their IOS devices. In essence, “… its going to be a long, long time”. As Sir Elton once sang

Thankfully too, jazz and jazz vocalists always seemed to be done pretty well, then and now.

Pink Floyd sounds bad?

Unabashed blatant Heresy!

The trying not exceed 20% of an amp's power was specifically mentioned by Ralph for SET tube amps due to their nature in how they distort. As I understand his point, I went back to read it carefully, one must be particularly careful with speaker matching with this type of amp by avoiding higher order harmonics.  

His statement does not include SS, Class D, OTL and other type amps.  Ralph, could you please confirm.

Blindjim ;

I took a peak down this rabbit hole as well as the one next door addressed as high efficiency speakers .

One of the responses by Ralph addressed the difference between the requirements of SET amps and PP amps . He stated the same desirability of running a SET at a maximum of 20% power . But then he stated how PP amps really needed some power to sound their best ... like maybe 20% + power .

After peaking down the HE speaker rabbit hole , I found it difficult to find speakers that were affordable , at least halfway aesthetically pleasing and suitable for my situation .

Right now I am content with what my current PP amp is doing and seeking improvements in other directions . I have spent quite a bit of time rolling input , driver and power tubes to get where I am .

While I still may seek out a SET amp in the future , I think that I would have an easier time finding one in the PSET realm where speaker choices would be more plentiful due to the added power of the topology .

Have you given any thought to PSET's ?

On a different note...I believe that you are in the TB area . Where would you go to hear different tube amp demonstrations ?

Good Luck .

What am I missing?
Grannyring got it in one- well done!

Apparently that this applies specifically to SETs and not to other kinds of amps. For example, despite being zero feedback (like SETs), our amps make a fraction of the distortion at full output (about 0.5% if set up correctly) so you have a much greater *percentage of usable output power*.

I like to use that idea of ’percentage of usable output power’ as its a number that can vary widely from amp to amp. Generally speaking, tubes have greater usable output power than solid state amps seem to have but SETs are the exception.

This is all about distortion, which all amps make so the ’percentage of usable output power’ has to do with the **kinds** of distortion that are particularly objectionable to the human ear. These are the higher ordered harmonics (5th and above, particularly the 7th), IM distortion, and in the case of class D, inharmonic distortion (caused by intermodulations with the scanning frequency; similar to aliasing in digital audio).

Because the ear converts all forms of distortion into tonality (including aliasing), the distortions above all manifest as some form of brightness and hardness. By contrast the lower ordered harmonics are perceived as ’warmth’ and ’bloom’.

Its quite worthy of note that these objectionable distortions always occur in very small amounts as opposed to the lower ordered harmonics- the issue is that the ear is far less sensitive to the lower orders. In this regard I propose a ’weighting’ scheme so that trace amounts of higher ordered harmonics can be seen for what they really are- which is to say: audible!

In SETs, the first onset of higher ordered harmonics is heard as ’dynamics’ by the ear as musical energy often occurs on transients where greater power is required (in a way fundamentally different from solid state, which tends to make the the higher ordered harmonics all the time). What happens is the higher ordered harmonics (to which very importantly the ear uses to calculate sound pressure) are thus only showing up initially on the leading edges of transients and no where else, so then it is perceived as ’dynamics’. The problem is, once you are aware of this fact its easier to hear that what is really happening is the amp is making distortion. So the simple act of reading this paragraph may have ruined it for some people. To avoid this you simply need more power or more efficiency. More power in an SET means it won’t sound as good and therein lies the dilemma!

Of course all forms of distortion are to be avoided, but avoiding the the objectionable forms is far more important overall for a pleasant listening experience. This, in a nutshell, is why tubes are still around nearly 60 years after being declared ’obsolete’.

One thing that has really become evident in the last 15 years or so is that if the loudspeaker is a higher impedance that avoiding the more objectionable distortions is easier to do **regardless** of the amplifier technology. I think speaker manufacturers are slowly figuring this out as there are more 16 ohms speakers now than there were 15 years ago. Put another way, if you are tying to make a lower powered tube amp sound like music, a four ohm load is absolute anathema!

Its my opinion and also my experience that four ohms has no place in high end audio (IOW if high quality audio production is in fact the goal). The cables are more critical and all amps sound harsher and less detailed on four ohms as opposed to eight or sixteen all other things being equal. Its not only audible, you can see it in the specs of any amplifier made.
This is such a great thread and I now better understand, technical reasons,  why I have been so frustrated in the past with some wonderful SET amps. The music was wonderful at lower volumes, and they did drive my speakers to go very " loud " I was initially impressed, only to find the sound not to my overall liking longer term.

It was this whole issue of sounding "loud" when a system should not sound loud when turned up. Rather, the performance should simply swell and grow with greater impact etc....

My mistake was not the particular SET amp, but pairing the amp with a 4-8 ohm speakers with sensitivities ranging from 89-93db.  My 8-20 watt SET amps, while playing these speakers loud, always fell a little short of greatness. Greatness at low, moderate, and higher volume levels.


Very nice information,thank you.

I quess in the golden days of audio weren't most speakers 16 ohm to be more tube friendly in that respect.

The irony is that the vast majority of high End speakers are in the 4 ohm range. This  suggests that either, 
1 4 ohm load impedance speakers are easier to design/build.
2  An assumption that the majority of buyers plan to use solid state amplification. 
3  The designers/builders simply believe that the speakers sound better with the lower 4 ohm impedance. 

My SET and 2 push pull amplifiers all mate beautifully with my 14  ohm speakers. I do believe Ralph's assertion that higher speaker impedance is beneficial to all amplifier topologies.  It seems many speaker builders would disagree with him given the predominance of 4 ohm speakers in the marketplace. 
I've returned to using my Silverline Preludes (allegedly 91 db) as they sound astonishingly good with the Fire Bottle HO (the HO…it's a HO)…along with 2 REL subs. I understand completely about the obvious benefits of higher efficiency speakers with lower power amps, so I was surprised at how well the Preludes are working…absolute clarity at the levels I choose to listen, and I'm very picky about noise and distortion. You can simply turn the amp up to test the limits (at a certain point it just loses it's mind), and at my normal listening levels which are plenty loud at times, the little amp works splendidly with surprisingly clean dynamic punch . Note that I've been using the Preludes for years, and with this amp listening at low levels (late at night generally) is far more detailed and enjoyable than before the HO was installed. Dennis Had claims that pretty much any great speaker will work with this amp, the only limiting factor being ultimate level constraint due to efficiency. 
I guess in the golden days of audio weren't most speakers 16 ohm to be more tube friendly in that respect.
Of course!

1 4 ohm load impedance speakers are easier to design/build.
2  An assumption that the majority of buyers plan to use solid state amplification.
3  The designers/builders simply believe that the speakers sound better with the lower 4 ohm impedance.

My SET and 2 push pull amplifiers all mate beautifully with my 14  ohm speakers. I do believe Ralph's assertion that higher speaker impedance is beneficial to all amplifier topologies.  It seems many speaker builders would disagree with him given the predominance of 4 ohm speakers in the marketplace.

The vast majority of amplifiers are solid state. These days most of them are safe with 4 ohms, and further many of them can double power into 4 ohms. In this regard, many speaker manufacturers are seeking to make (under a false impression) to make their speakers more compatible with solid state and thus secure a greater market. Its a good example of dollars being the goal rather than the ultimate in sound reproduction.

If they were to simply raise the speaker's impedance and keep all other things the same (which in many cases would be a bit of a trick) they would find that their speaker is sounding smoother and more transparent, regardless of the amp they use.

There really isn't any point in making a speaker that is 'difficult to drive' as the result will be more distortion, of a type that will cause the amp to be harsher and less detailed. You can see it in the specs.
Blindjim- I found the same exact thing as Grannyring when I was using SETs (no surprise, one was the same exact amp, and neither of us has ultra-high eff speakers):
The music was wonderful at lower volumes, and they did drive my
speakers to go very " loud " I was initially impressed, only to find the sound not to my overall liking longer term.

It was this whole issue of sounding "loud" when a system should not sound loud when turned up. Rather, the performance should simply swell and grow with greater impact etc....

My mistake was not the particular SET amp, but pairing the amp with a 4-8 ohm speakers with sensitivities ranging from 89-93db.  My 8-20 watt SET amps, while playing these speakers loud, always fell a little short of greatness. 
I have zero and I mean zero technical knowledge but everything that Atmasphere has posted has turned out to be true in my experience.  If you do not want to be confined to ultra-high efficiency speakers I think this means you can rule out the 2A3 and 45 amps.  If you want to go SET, you will probably want something 6C33C, 211 or 845 amps with a moderately high eff speaker (95--96 dB).  I found that 300b and EL-34 SETs did not cut it in my 14 x 23 x 8.5' room, driving 95-96 dB speakers, listening mostly to the same type of music as you do.  Great sound at low-moderate volume, but when you get grooving and want to go a little bit louder, the sound starts to get less enjoyable and fatiguing.  OTOH, my 300b push pull that makes 27 wpc (VAC Ren 30/30) or my 6AS7G OTL that makes 30 wpc (Atma S-30) sound fantastic. 

I think it should be obvious by now that if your speaker or your amp selection is priority one, then you have to get a "matching" amp or speaker.  If you go moderate efficiency, or 4 ohm on the speaker, you are going to want a reasonably large, SS amp, of which there are many.  OTOH, if you decide first on a 45 SET, you are going to be restricted to a fairly small group of very high eff speakers (>100 dB/w/m).  Those are the two extremes.  If a tube amp is your first criterion, and you don't want to be restricted to the v high eff speakers, IMO, you will want something in the 25-30 wpc range (or greater) paired with moderately high eff, 8-16 ohm speakers.  To get that, you can go OTL or you can go push-pull.  The very high output transmitter tube SETs are, I believe, out of your (very generous) budget. 

To get back to your original question, I am persuaded by my limited experience and the technical explanations of others, that the differences between the "voice" of different output tubes is outweighed by the requirements of your amp/speaker combo.  Particularly with SETs, the power requirements dictate the tube choice.  As you go to push-pull or OTL designs, you have more flexibility in terms of both output tube and speaker efficiency.  Both Berning/LTA and Atma-sphere offer a range of power output options in OTL designs and some variation in tube types.  Push-pull designs offer the widest range in tube types and power output, giving you the widest range of tube-friendly speakers to choose from. 
Hi Swampwalker,
Nice comments, I also suggested the VAC Renaissance 30/30 or a high quality moderate power class A push pull tube amplifier. As you note they do offer increased speaker choice flexibility and are easier to build a system around for most people as well. 

SET will frustrate some people and will require more of a thought out plan of action. It’s worked out very well for me but I knew what was needed and was prepared for it. By the way I am not saying that you weren't prepared for SET,  it just didn't meet your particular needs. 

In addition to the VAC REN amplifier, believe that the Atma-Sphere S-30 , M-60 and the Linear Tube Audio ZOTL 40 would serve Blindjim well. Wolf Garcia seems to be getting results/outcome quite similar to mine.
@swampwalker, +1 big time!

I have been talking to Ralph at Atma recently as I do want a second amp and want for it to be tubes. SET amps will not work with my current speakers. 6 ohm, 89db sensitivity in a very large room.

In order for a SET amp to work for me, it would need to put out 100 watts. Some amazing SET amp! An OTL or PP tube amp could do the job at 60 watts. Especially OTL with the Zero autoformers by Paul Speltz. 

@swampwalker I remember the amp! I purchased a set of 300b monos from you also! I think we have sold each other gear several times over the years.
Yeah, Ralph confirmed what I have always felt. SET amps are not for most of us, this includes cost. Low impedance speakers is not how it should be.
Ralph, besides Classic Audio, what would you recommend to use with your amps? Also, do you believe that short length Mogami RCA cables are just as good as XLR? I mean 2497 wire.
Hi Bill,
I'm very familiar with the Atma-Sphere MA-1 mono blocks,  are you considering these or the M-60s with your Crescendos?
I owned the MA1s when I had my Soundlab speakers. Great amps. I don’t want quite that many tubes. The 60s may be my only real choice.
Would their 60 watt output satisfy you given what you described as the demands (89 db and 6 ohm impedance load)  of the Crescendos?
@grannyring- I forgot about the 300b monos. 
@blindjim  - Grannyring and I went the same route; from 8-9 wpc 300b to 12 wpc EL-34 SETs with the same results.  My speakers were quite a bit more efficient than his (92-95 dB/w/m, 8 ohm nominal, flat impedence) but we both found that Atmasphere was right; when you are down in 10 wpc range, you need +/- 100 dB speakers and/or high impedance speakers if you want more than moderate volume levels in a mid size room.  I know Charlesldad (and others) have had great luck w 300b SETs driving somewhat lower eff speakers, but IIRC, his speakers are 16 ohm. 

Of course, you COULD opt for the WAVAC HE-133 150 wpc SETs @ $77K.  That would maximize your choices for speakers, if in fact you had any $ left over to buy speakers ;-)
Well great question. Since the OTL amp does not carry the 20% of rated power caution that Ralph has been talking about, and I have experienced, then the Crescendos can use all the watts available in the M60. Better said, most of the power available.

Also, adding the Zero autoformers actually increases the power output of the M60s by some 50%. So the speakers would be utalizing, in effect, 90 watts.  Yes indeed this would work great.

Just have to decide if I want that many output tubes. I suppose it would be better to get a 12-16 ohm, 95db or better sensitive set of speakers😬

However, I did love the sound of Ralph’s amps. Uncanny resolution and sense of being right there in the midst of the performance.
No need for Wavac. LAMM ML2.2 would do for many situations. Only $20k or so used.
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Good points @stfoth,

We have to remember 50 watts with an 805 tube etc, is still a SET amp and the 20% rule comes into play. Speaker matching is still critical. Will it work with a 4-8 ohm, 90db effecient speaker? It depends. Big room, like to listen at 85-90db levels at times, sit 10-12 feet back, then it won’t.

Small to moderate sized room, 70-80db listening, 8-10 feet back from the speakers, then it may work wonderfully indeed. Once the room gets bigger and you want to turn it up more often, then you enter a real risky area. Sometimes your happy, sometimes not with that system. Can be a frustrating place to be.  


Keep the Knowledge coming,

Best thread on audiogon presently.

I'm getting good factual info that were kinda grey areas to me and this thread has educated me well.

I thank you all,

Kenny, I am working on a 300b mod to my Lyngdorf unit. I will update once finished. I call it the "1DadDHT" mod package. Pictures coming soon! Charles, you will be asked to beta test.