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
Hello,
I happen to agree with your comments. This is why I often state that you actually have to listen to a component/system to get to the truth. Otherwise it’s far too easy for preformed opinion to be presented as fact. I have 94 dB sensitivity/ 14 ohms speakers that I originally drove with 100 watt PP tube amplifiers(60 watt in triode mode) and this match was exceptionally good sounding. 

Strong curiosity led me to purchase an 8 watt SET amplifier (mono blocks) using 300b tubes seven years ago. For my particular listening needs and taste the 8 watt SET improved my system’s presentation and moved it to a higher level. In other words I went from legitimately "very good " to superb . It all depends on what musical and sonic parameters are most important for a individual listener. I’m glad that I took the chance to try the lower power amplifiers. The crucial key is defining what type of sound you are looking to achieve.
tommylion:
Of course you are correct that SET amps can provide an exquisite and special listening experience. The key is your wise words "carefully chosen speakers". Your Audio Note speakers are specifically designed for your type of amplifier and listening. The AN web site basically states to get the best results -use a SET amp.

I have a horn system and also a dynamic driver Teresonic system.  The horns are driven by the 300 B SET amp and the Teresonic by the 45 Tube SET amp. I think both provide a special intimate and moving musical experience.

A big problem I see repeatedly is speakers being sold that are not efficient but somehow are so special in some sort of novel design that they will perform to their optimum with a SET amp. Buyers then give the SET amp a bad rap for lacking dynamics or bass when the seller's hype exceeds the laws of physics.

I hope to try the Emission Plate mesh tubes some day. From what I have read in the just right system they add a special touch. Congratulations on having that system.

David Pritchard
Great comments,
Could not agree more. Happy listening, best, Rob

Indeed, high efficiency and high impedance speakers are common factors when you read/hear someone is happy with a SET amp. Another factor is the SET should be driven "well below" its rated power, which is of course undefined how low is low enough.

I'm in the process of building an active system with SETs for treble and midrange and class-D for midbass and subwoofers. It's said power required below and above 350Hz is about the same, so by crossing around there (or higher) you relieve the SET from carrying half the load. If you further divide the upper range into two, then each amp will carry 1/4th of the load.

I have my eyes on Yamamoto's A-08S (45 SET), and while the speaker driver options aren't super wide, there seems to be enough. I guess demand pulls for drivers where high efficiency and impedance aren't as big a deal, the manufacturers follow suit. It is being a fun journey!
The Yamamoto A-08S is on my list, if I come into some unexpected cash. I'd run it into my ANs (92 db?) full range, just like I'm doing now. I'm sure it will have enough "slam" for when I play The Killers. 90 db is LOUD!
Excellent, informative posts from my fuse-loving friends above.  ;-)  I have two Dennis Had amps, an SET and and SEP amp, one based on EL84 and the other on nearly any power tube you can get into the sockets, from EL34 to KT150's.  16 wpc and 6 wpc, respectively.  The smaller amp is sublime mated with the Spatial Audio Holograms and the bigger one drives my Zensor 3 speakers in the bedroom, both with all the power I need.  They both have a warm euphonic sound.  Rolling tubes is joy with these amps and some of the new tubes are as good as the pricey NOS tubes I have heard, particularly the Gold Lions.   
A type 45 can make about a 1 watt or slightly less running single ended.

To really appreciate what they can do (which is to say, they usually sound better than a 2A3 or 300b amplifier) you actually do need some efficiency and the only way to get the efficiency you need is with a horn system unless you are in a really small room, perhaps a closet.

If you drive the amp too hard, the odd-ordered harmonics that the ear uses to gauge sound pressure will appear. This causes the amplifier to sound 'dynamic'. In the initial opening post, we can see that this is happening. Its important to understand that this 'dynamic' quality is really the result of distortion appearing on the transients where most of the power requirements exist. Its a physiological interaction with how we perceive sound.

The problem is, once you know this, you can perceive it as distortion, not just 'dynamics' (in about 90% of audiophile conversations, the word 'dynamics' can be safely substituted with the word 'distortion' without changing the meaning of the conversation). So if you have read this far, I may have wrecked it for you.

You can prove this easily enough by obtaining a sound pressure level meter. They are available as apps for smartphones. You will see that its really not playing that loud- it just sounds like it due to distortion.
Atmasphere raises a valid point however context is essential. How loud is loud enough ? Clearly there’s no single right answer as limits are individually set by a listener. We all determine our respective comfort zones of SPL(sound pressure level). Tommie’s Audio Note speakers are 95-97 db sensitivity. If he listens at say an average SPL 75-80 db he’s using mini watt power i.e. small fractions of 1 watt. Depending on room size and music genre he is likely as happily content as he describes. The vast majority of his enjoyable listening could be occurring in the mini watt power region. numerous variables must be considered. "Just right" volume level for one person may be too soft or too loud for another.


Tommie what SPL do you typically listen at in your home? Not everyone seeks 100-110 db peaks.it all depends on what makes you satisfied.
I have owned many 45 SET amps as well as loads of other SET to get the best out of 45 I have had to biamp even on horns the 45 SET doesn't drive woofers well but is amazing  on horns. I have had some luck using with fullrange BLH with 45 SET. But I do see many SETing themselves up for failure by not matching loudspeaker to amp. 
When I checked my levels in the past, I didn't get much above 90 db on peaks. That was setting it as loud as I would ever want to listen. Most of the time, it was lower than that. 100 db peaks must be painful, not to mention the potential for hearing damage.

I'll have to pull out my db meter and check again.

I use an autoformer passive preamp. My understanding is that, in contrast to a resistive volume control, the output impedance gets lower as you lower the setting. This results in better sound at lower volumes, which corresponds with my experience.
Hello Tommie,
Given your preferred listening levels and comfort zone I can understand why you are satisfied with your 45 SET and Audio Note speaker match, Congratulations. As I mentioned earlier not everyone desires or wants to listen that loudly (100db or greater peaks). This is strictly an individual preference issue. If you have good hearing ability (and want to preserve it) your limits of listening volume would satisfy many other listeners as well. To each their own as the saying goes. Tommie 100 db SPL is loud (though not necessarily uncomfortable). I’ve measured this level at live venues with unamplified instruments and even under these natural conditions (no electronic distortions via PA system) it’s definitely perceived as loud. I’m assuming that a listener is without some degree of hearing loss. Otherwise perception of loudness would certainly vary.
Charles,
Just just to make things clear, I'm not saying one can pair 45s (or other low power SETs) with ANY quality dynamic speakers, and expect good results. However, higher efficiency dynamics, that are known to present a benign load (like the Audio Notes), are a very viable option. Especially if you prefer to listen at low to moderate levels.

When I checked my levels in the past, I didn't get much above 90 db on peaks. That was setting it as loud as I would ever want to listen. Most of the time, it was lower than that. 100 db peaks must be painful, not to mention the potential for hearing damage.
If 100 db peaks are painful, either you already have some sort of hearing damage or the amplifier is making a lot of distortion. The measure of any good system is the quality wherein it is not easy to figure out how loud its playing without instruments (sound level meter) or trying to talk to someone beside you and be heard. IOW 100 db peaks should be effortless and relaxed!! Usually when a system sounds like it is loud or verging on painful that is a sure indication that distortion is playing a role.

The usual solution is more power so that the amp will not make distortion.

In Tommy's case, with only about 0.75 watts to 1 watt available, the maximum power before higher ordered harmonics appear is likely about 0.15 watts to 0.20 watts. The sound pressure with the Audio Notes at 1 meter is thus about 90 db (less at greater distances) before harshness sets in. From his comments it appears to me that he is routinely pushing the amp too hard- he is likely further from the speakers than just 1 meter.

Unless he's listening in a very lively environment or in a very small room, the simple fact is that a more efficient speaker will bring out a lot more of the magic that 45s have in spades (I have type 45 amps BTW; my speakers are 98 db and the amps fall flat on their face because they simply don't make the power. My room is 17' x21'.). This is one of those situations where context is everything as Charlesdad points out. For example, as a desktop setup this would be pretty sweet. But for serious home listening I'd want a speaker that was more like 107 db, such as the Hartsfield or something like that.

The magic of SETs comes from the fact that as power is reduced, so is distortion, down to the point where it becomes unmeasurable. When you are running distortion this low, the result is that more detail is revealed as it is not obscured by the distortion due to the human ear's masking rule. A type 45 amp no if ands or buts has wider bandwidth than higher powered SETs- that is why it sounds better. If you really want to hear what that is all about a high efficiency speaker is mandatory.
My approach is I want to be able to enjoy listening at any practical volume needed. The only way to accomplish this is to avoid clipping and distortion.

One might be satisfied with lower volumes only but if speaker amp integration is not done well one may practically have no other choice.

Also distortion usually sets in at subtle levels that may not be clearly audible well before one becomes aware of a problem.

One may certainly choose to not care about these things but they are real issues to consider and understand for best results in most any case IMHO.



"100 db peaks should be effortless and relaxedd" Atmasphere wrote. 
I understand your point however that is a loud volume and is perceived as such via healthy ears. I previously cited this volume le jazz club I frequently attend. It's an intimate environment with the musicians unmixed probably 90%of the time. 

You're listening to the pure sound straight from the instruments without the imposition of electronic distortion. Under these ideal circumstances when they hit the 100 db level "it sounds loud". Painful or uncomfortable? No,  very loud? Yes. My point is some listeners would want to duplicate this at home and some would not. Either is preference. 
Many lesser solutions have their charms. People choose or settle for them all the time.

The merits can be argued subjectively only. Often that’s enough for many of similar mindset.

Its just one of those things that some may go completely gaga over for good reasons but probably not so much with those who care more about technical aspects or what works best together or not and why.

I am a big fan of the 45 tube.  I have heard it used in parallel single-ended, pushpull (I own a pushpull 45 amp) and in single output tube single-ended configuration.  It delivers a very punchy, clear and detailed sound when operated well within its upper output limit. 

I think someone can effectively utilize a 45 SET amp with the AN-Es in a smaller room, provided that one accepts that it will not be able to play at high volume levels.  I am quite familiar with the AN-E and I have heard it with some fairly low-powered amps; a local dealer frequently pairs the AN-E with an Audio Note Kageki amp which is rated at 6.5 wpc.  I can hear the limitations of this amp when playing demanding music, such as large choral pieces.  The music begins to suffer from compression and becomes muddled and unfocussed to a slight degree.  But, these are problems I can see someone living with because, for the VAST majority of the time, a good 45 amp will sound great.

I do agree with Atmasphere that a 45 SET is really best used with extremely high efficiency horn systems.  A friend had such an amp for his107 db/w system and it sounded great.  That kind of combination can be recommended without much reservations; the use of a 45 SET with something like the AN-E can only be recommended with the caveat about limited volume levels.

It's like a car that only drives well on quiet perfect straight roads in sunny weather using 95 octane gasoline at 50 miles per hour and needing service every 1000 miles at most. In some cases it will do but, generally speaking, it is, if you will forgive this, ridiculous. Atmashere was very very polite.
To me, having an amp that sounds not as good as the 45 SET (if that is one's preferred sound) when playing at the regular volume one listens at, just to have the capability of delivering clean sound at extreme peaks when listening at higher levels is more "ridiculous;" I'll take better sound for 99.99% of the time and sacrifice quality for the brief moments when higher peak output would be desirable.  It is all a matter of what compromises one is willing to accept.  I don't know of a single component, at any price, that I thought was free of some performance compromise in certain respects vis-a-vis another.  I am in agreement with Atmasphere that the use of a 45 SET amp by the OP is not "ideal," but I also agree with Charles 1 dad and the OP that one can really like such a combination, particularly if one can live with the "compromise" of more modest listening levels.
Also, power is felt. Listen to the same music with the same 105 db speakers at the same db level, not loud, with equal quality amps that have different power capabilities, and there will be a difference.
That's why live music sounds so different - it has the power that cannot so far be either fully captured on the recording or reproduced.
Yes, certain aspects of midrange are best reproduced by particular design amps, but not all aspects. And there are other frequences and other things that are much more important. Sophisticated textures are great but other aspects far outweigh this.
A 45 if used just on a mid horn of 106db plus is a wonderful thing and if possible one should try to hear such but if poster enjoys the 45 with the AN nothing wrong with that. 2nd order can sound good to the ear. Enjoying our system choice is what its about not if its optimal or not, so if you like it dare I say its right.
Yes the main point is it is not "ideal" but yet another compromise with trade offs that some perhaps many might easily live with.

A watt or two can also go much further when highest and lowest octaves are rolled off. That’s a reasonable trade-off as well that some systems might offer over others. My decent sounding table radio works that way. :^) Midrange freaks can be in nirvana for not as much. you might even hear things in recordings not heard on many much larger and more powerful systems.

Or if size and cost of speakers is no issue, and you are not adverse to large horns (good ones are very pricey), then you should be golden in the end with just a couple precious watts. Now that’s an option I think I might definitely be able to live with in the right house/room designed with that in mind.  But its not where I am at currently.




Inna I don’t think your automobile analogy applies to the OP’s situation , it seems rather you have projected your own specific desires and preferences.
If anyone reads his comments carefully it’s very evident that he’s quite happy with the performance of his system’s sound quality. It seems that Larryi recognized this obvious point. Others are suggesting that they wouldn’t be satisfied with this amp-speaker pairing( peak volume  limits?).  That’s fine however they aren’t the OP who happens to be very pleased with what he has. I can certainly understand why he is.
Charles,
100 db peaks is definitely desirable in a good hifi system. In fact it should be a basic criteria while choosing the speaker-amp-room combo. But 100 db continuous SPL is very loud. 
Charles, I was not talking about the OP's situation and preferences. My car analogy was intentionally grotesque and should be taken as such. I wanted to emphasize particular points not discuss the subjectivity of one's happiness.
I too could have SET low power amp based system but that would not be my main system.
Let's not drown in subjectivity because that would be the end of a potentially interesting discussion. Most of the time Audiogon is a very boring place.
Hello Inna, IMO nearly  the entire endeavor of assembling an audio system is subjective.  You listen to components and it is either yay or nay.  You either like the resulting sound quality or you don't. Listening to music is an emotional experience.  How does one eliminate the obvious and innate subjectivity aspect? Who decides their satisfaction with components/system without use of their ears?
Charles, 
Charles, of course it's an emotional experience and I would be the first one to defend the subjectivity, I just invited everyone not to get cocooned in it while communicating and conveying certain aspects of the subjectivity. Even each instrument has its own 'subjectivity', in a manner of speaking, its own unique voice. However, low powered system, or an instrument, would have too many limitations, and no matter how great it may at times sound, this would not be enough for me. Speaking of instruments, the greatest I've ever heard was a Conti custom guitar played by Paco de Lucia. Yes, it was made as a flamenco guitar not classical or blues guitar, but I am quite certain it would play anything extremely well. If it was still a compromise - it was a great one. Anyone heard Amati or Stradivarius ?
I have no problem with someone who tries a low power SET amp with well matched dynamic speakers, and concludes it doesn't work for them. What bothers me is that all the talk about these amps REQUIRING 100 db + efficient speakers dissuades people from even trying a setup like mine.

They may find it doesn't meet their needs, but they may also be very pleasantly surprised, like I was.

One of my most memorable experiences was listening at home after attending a live orchestral concert, and thinking "Wow, this actually sounds like what I heard in the hall!".

Massed strings in the concert hall can have this amazing "singing" quality, which is hard to reproduce at home. My system got it right (among many other things).


IMO nearly  the entire endeavor of assembling an audio system is subjective

I started out that way because I basically knew nothing about how this stuff really works.   I even lost interest for years because my sound was not what I wanted and I was too lazy to figure out why. 

Things changed when I started to focus on really understanding what was going on.    I was on teh right path soon after and finally found a happy place after not too long.

There is a difference between what one likes which is subjective and the decision making process that gets one to their goals.   That is best driven by objective learning to meet ones subjective goals.

Everyone ends up differently as a result because we all have different goals but there are right and wrong approaches to most any undertaking.  
2nd order can sound good to the ear. Enjoying our system choice is what its about not if its optimal or not, so if you like it dare I say its right.
The concern of course is not the 2nd harmonic, but the presence of the 5th and above.
100 db peaks is definitely desirable in a good hifi system. In fact it should be a basic criteria while choosing the speaker-amp-room combo. But 100 db continuous SPL is very loud.
This. 100 db peaks should be no problem for any system, that is if you want to be able to reproduce 90 db correctly. Most peaks don't show on a sound pressure meter as high as they really are due to their transient nature.
What bothers me is that all the talk about these amps REQUIRING 100 db + efficient speakers dissuades people from even trying a setup like mine.
I think you might be missing my point. Clearly there is something about that type 45 amp you like. My point is that with more efficient speakers you would like it more, as the more efficient speakers can bring out more of that that amp can do right. I am speaking from direct experience here as I have had type 45 amps at home for years.


My point is that with more efficient speakers you would like it more, as the more efficient speakers can bring out more of that that amp can do right.


That’s a very good way to put it and not just in this more extreme case (only a few good watts available) but in all cases amp/speaker integration is one of the most fundamental things to address and get right. Otherwise it may still sound good within limits but you may not be getting the most possible out of your overall sound investment  and you may not even know what you are missing otherwise.
Hi Inna,
I appreciate your input and perspective. At the end of the day we all develop audio systems that reflect our sonic destinations. From reading various post from you I realize you ideal setup would favor high power tube 0r SS amplifiers, I understand that choice .We have very likely experienced different outcomes with low power tube amplifiers, no problem.

My last owned transistor amplifier was a Symphonic Line RG7. It was a very fine amp. In my listening it doesn’t measure up to my current SET amplifier overall and particularly in the areas that matter most to me. Common sense and experience dictate that no amplifier or component is without some flaw and thus compromised. Given your objectives I believe you’d prefer the Symphonic Line, I get that. No matter how you cut it ultimately selection is based on what we hear in our systems. As is evident here that will vary greatly amongst listeners.
Charles,
Hi Charles,
Yes, I would prefer high powered tube or hybrid amp. However, ideally I would have two different systems. One system is a compromise too. The music I listen to varies from acoustic guitar and vocal to world music to jazz fusion. The amp doesn't have to be insanely powerful, just great 100 watts and efficient enough speakers. For medium size room this would be just right.
Symphonic Line I might try too later if I can find it, or older Gryphon, before I go with tubes or Lamm hybrid.
I appreciate your input too and understand , I think, what you are saying.
Inna,
I hope you have an opportunity to hear a Symphonic Line power amplifier. They’re very high quality solid state designs  and I believe you will  be impressed with them.
Charles,
The idea would be to upgrade my Redgum integrated with better integrated, preferably with Symphonic Line or Gryphon, or perhaps Gamut or Vitus. I also would like to replace my AcousTech phono with a tube one, an excellent tube one, Lamm or VAC etc. And then go with top level separates. I guess, Ypsilon will be out of reach unless one day I can find a used integrated. Still, I would most likely prefer Lamm of VAC or Atma-Shere separates to Ypsilon integrated, or it just might be different.

Inna,

Some other integrated amps to consider include something from Vinni Rossi (can be configured in MANY different ways, including tube stages) and Lavardin and LFD integrated amps (simple, really nice sounding medium power integrated amps).  I've heard these with speakers that were moderately efficient (Harbeths, Audio Note, J.M. Reynaud).

As for a phono stage, Zanden makes a few nice tube and solid state versions; the most fun feature being a choice of different equalization curves.

I have heard the Symphonic power amp Charles mentioned and it is really very good for solid state. 

Larryi,
I'll stray off topic one last time 😊.  One of the very best sounding SS amplifiers I've heard are the Concert Fidelity ZL 120 and their ZL 200. This little known Japanese products sound absolutely fabulous.  They're hardly ever written or talked about, too bad. 
Charles, 
Larry,
Thank you. Never heard of Vinni Rossi. Zanden is very high end.
Charles, 
Concert Fidelity, are they more to your taste or mine as you see it? Or both?
Hello Inna,
I can’t honestly say that I know your musical/listening taste, rather I recognize that you prefer amplifiers of a certain power range. My taste is unambiguously towards the natural/organic sound with tactile realism.
The Concert Fidelity  SS amplifiers do that exceptionally well. I’ve only heard them with their sibling tube Line Stage which only further helps I’m sure. It’s a pure and natural sound character rather than electronic (the bane of many SS amplifiers IMO).
Charles,
I am using a Yamamoto A08S SET 45 with EML mesh tubes, driving a pair of Zu Audio Druids in a dedicated listening room about 15'x18' and the result is just stunning.
The transparency, detail, tempo, balance and realism is far beyond anything I've ever owned before, or even heard with other people's systems, some costing 10x and more. The cost of my amp + speakers (new) is less than $9K. I couldn't be happier with this setup.
True, it doesn't play nearly as loud as my living room 60lbs, 700 Watt Classe SS amplifier, and I don't expect it to.
When I want to turn the volume up and listen to hard rock, metal or electronic music at live concert levels, I do it in my living room with a system that excels at that :-)
Maybe one can have both worlds. I haven't found that setup yet, but I can only guess is that if it does exist, it will probably cost 20x more than both my systems together.
Ami, that's one of the things that I said - two very different systems.
Charles, of course I like what you do as well. But that's not all. Even flamenco music requires speed an drive let alone Mahavishnu Orchestra's jazz fusion. Bass is important too. Not exaggerated, but just as it was recorded.
It does appear that I strongly gravitate to Lamm/Atma-Sphere camp. Never heard VAC or Allnic let alone Ypsilon and Absolare.
I'd read a lot about 45-based amps requiring very efficient speakers (over 100dB), but I've run 45 amps by Korneff, Burgess and Yamamoto with Vaughn Triode speakers (97dB) with great success. 

My room is 21'x19', I generally don't listen to very loud music (in the mid-70dB range) , but the system was capable of much more and with a wide variety of music. 

Ultimately, I went back to Harbeth with a high-powered SS amp, but I do miss the lushness and intimacy of the 45. 
Hello Ralph (Atmasphere).

I've seen your comments before and I am keeping them in mind as I design/assemble my new system, a 4-way active. 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?

Thank you!
Inna,
I will tell you that timing, musical pace,flow and drive are strengths of my SETamplifier be it small bands or larger combos. But again I don’t know what SET amplifiers you’ve used or are familiar with. As with any other genre of components there’s a hierarchy and broad spectrum of performance.

If you look at my system page you’ll see a picture of 3 sets of mono block amplifiers, my SET,my 100 watt push pull and a borrowed Lamm push-pull 90 watt amp. Of these three choices the SET mono blocks were the best sounding driving the same speakers in my room. I appreciated the generous loan of the Lamm from a friend. It’s the most expensive of the three amplifiers but wasn’t the best sounding.

Now again that is only my assessment based on my taste and my system. You or someone else could rank them differently and that is easily understood. What moves me may not move another listener, no arguement on that point. It simply depends on what you want. We listen,compare and ultimately decide. If ever an undertaking was subjective, it is definitely High End audio and listening to music. The SET elicited the most emotion and musical communication/involvement.
Charles,
Hi Horacio (Lewinskih01),


My perception has been that Ralph is often not here on weekends, so I’ll give your question a shot while we await his more experience-based response.

The rough approximation you mentioned earlier to the effect that the 350 to 2000 Hz range within which your 100 db/W driver will be operated means that roughly around 25% of the system’s total power requirement would typically be supplied to that driver seems to me to be a reasonable ballpark assumption, for many and perhaps most recordings. If we assume that the amp is reasonably well matched to the driver’s impedance, and can put out a maximum of about 1 watt, the resultant 100 db maximum SPL at 1 meter would correspond to about 90.5 db at a listening distance of say 3 meters, neglecting room effects. Two speakers can be expected to raise that by 3 db (and potentially by 6 db, depending on listening position, but let’s be conservative and assume 3 db). So that brings us to 93.5 db. As a very rough guess let’s assume that room reflections would raise that by another 3 db, to around 96.5 db. Given the 25% assumption, outputs from the other drivers would raise the total maximum SPL to around 102.5 db.

To avoid operating the amp above say 25% of its power capability (Ralph mentioned numbers equivalent to 20% but using 25% eliminates the need for me to pull out my calculator for the subsequent calculation), 6 db would be subtracted from that amount, resulting in a maximum SPL at the listening position, with the amp operating in its presumed comfort zone, of about 96.5 db.

That will be good enough for the great majority of recordings for the great majority of listeners, IMO. However recordings having particularly wide dynamic range, such as well engineered minimally compressed classical symphonic recordings on labels such as Telarc, Sheffield Labs, Reference Recordings, etc., could very possibly put the amp out of its comfort zone, IMO, and perhaps even occasionally drive it into clipping, on very brief high volume dynamic peaks. Even though those recordings might be played back at average levels of perhaps 75 db or so.

I have many such recordings, that I listen to fairly regularly, so for me a system must be able to cleanly generate SPLs of 105 db at the listening position to be acceptable. For most recordings, genres, and listeners, however, I suspect that a maximum capability of 96.5 db would be fine. Especially given that the amp could provide 6 db or so of additional capability if occasionally necessary, albeit with some increase in distortion.

For an example of a recording having exceptionally wide dynamic range (although in this case the highest volume levels are reached on notes having much of their energy in the deep bass region), listen to the last five minutes or so of the ca. 1979 Telarc recording of Stravinsky’s Firebird Suite, Robert Shaw conducting the Atlanta Symphony Orchestra:

https://www.youtube.com/watch?v=Y5Or4x6RXyU. (Feel free to ignore the images).

Note how the volume of the music descends to barely a whisper shortly before the start of the finale at 17:25, and then rises to a concluding note that with the recording played in my system at average levels of perhaps 75 db or so closely approaches 105 db at my listening position. The 30 db difference means that around 1000 times as much power is required to produce that concluding note as is required to produce the average level of the recording. And based on SPL measurements I have taken, and on waveforms I have had occasion to look at on a computer (using an audio editing program) for other recordings having comparable dynamic ranges, I feel fairly certain that the difference in volume between that note and the softest notes just before the finale is upward of 50 db. Meaning that more than 100,000 times as much power is required for that note as for the softest notes.

In contrast, my understanding is that many and perhaps most pop and rock recordings are dynamically compressed to less than 10 db, meaning less than a 10x difference in power between the loudest and softest notes.

So given also my belief that perceived "loudness" tends to be mainly a function of average volume rather than peak volume, and given that the system you are building should easily be able to handle the average listening level of 85 to 90 db that you mentioned, it seems to me that the dynamic range of the music that is listened to is what should be considered as having the potential to drive the amp out of its comfort zone, if not to its limits.

One further comment: Consistent with one of the points Ralph stated earlier in the thread, in the absence of detailed technical information for the specific SPL meter that one may use I would not assume that the meter and its microphone necessarily have either the speed or the frequency range to fully capture the maximum volume of a brief musical transient.

Continued best of luck with your project. Best regards,

-- Al

Charles, if I may ask, what kind of music do you mostly listen to ? Classical ? I am very familiar with live classical music especially big orchestra and opera music. I don't listen to it but I know how it should sound.
Charles, I took a look at your page. You appear to be into classical jazz a lot. What analogue source do you use, I didn't see any ?
Hi Inna,
Jazz is my passion,  live venues (2 to 3 times a month for about 25 years) and of course recordings. I was quite an analog dieheart for many years. Six years I’ve have my digital front end and it has been enormously satisfying, so no looking back. I never tire of hearing talented jazz musicians up close and personal (and they are a splendid template for the ears).
Charles,
I see. If your system sounds great with digital it would sound beyond that with analog. I know that you know it.
No,I don't believe that anymore, if so I would return to a turntable again. Both formats can be setup to sound superb and I can enjoy both equally well.  My opinion only, I know how heated this topic often becomes with analog aficionados 😊. I listen to excellent analog systems of friends and enjoythe experience quite a bit.  I'm just as engaged with my system.
Charles,