Power output of tube amps compared to solid states

Once again, I return to how radical a departure Arthur's posts are when discussing power in amplifiers.

Unfortunately, our posts are again dealing in the traditional means of trying to explain how the watts we measure in a tube amplifier versus a solid state amplifier still correlate in a 1 to 1 ratio. The point is, they don't. Well, at least, not in a useful way of the music / amplifier / loudspeaker relationship. As Arthur gave a glimpse of in such an utterly brilliant way in his initial post, tubes and transistors operate in VASTLY different ways. Like comparing an NFL running back coming through the hole on a play to a distance runner in a 10K event, both moving at 10 mph, living in a world where we use a steady state (linear, quadratic, or even cubic, etc.) measurement to compare them confuses the issue, and only delays us further from the questions and answers that will ultimately solve the puzzle.

Again, this is a question of calculus. Yet we're still attempting to shove it into an arithmetic / algebraic model. Sorry to say, but it just ain't gonna work. Until we come to grips with the fact that we need to operate under a completely different paradigm we're going to be splitting hairs on issues that bring us no closer to understanding.

Grant's question, "What's hotter, 85° in Miami, or 85° in Phoenix?" can get the dialogue back on track. Back in my days as a research chemist / material science engineer, I would use an analogous example in taking the first step in illustrating the difference between temperature and heat. When you open the 350 degree F oven you're baking a cake in, the air and metal oven racks / pans are obviously both at 350 degrees F. And while you are in no peril in putting your bare hand into the oven in contact with 350 degree air, you know not to grab the racks or pans which are at the same 350 degrees F without the protection of an oven mitt or potholder. Without going into the mathematics involved, the metal will transfer that 350 degrees F instantaneously into your flesh, the air does so in a much more gradual manner. In simple terms, that's the difference between temperature and heat.

What I'm getting at is we need to come up with the same type of "temperature versus heat" model when dealing with amplifier power. Then, we'll be capable of satisfying Unsound's relevant question.

The last thing I want to say is that we must also be on guard to not fall into the trap of trying to explain why some folks choose tube amplification as simply a matter of power. Power is but one piece in the puzzle.

I thought Ralph's point was that the choice might be because of the differences in the way tube and SS introduce different types and levels of distortion, not power per se. I do know this about power, I seem to want as little of it as possible, as long as it can make my speakers as loud, fast, and dynamic as I need them to be.

' I do know this about power, I seem to want as little of it as possible, as long as it can make my speakers as loud, fast, and dynamic as I need them to be."

That's a very good way to look at it !

"The last thing I want to say is that we must also be on guard to not fall into the trap of trying to explain why some folks choose tube amplification as simply a matter of power. Power is but one piece in the puzzle."

Good point. And probably not even the most critical one, at least in the simplistic terms usually applied to describe it which typically do not determine that your speakers are as loud fast and dynamic as they can or you need them to be.

Unsound, the point of my post was in fact that all humans do indeed use the exact same perceptual rules- that is what the research (science) has proven. Taste is something else entirely and not on the table here.

As Joe and Arthur point out, timing is everything. What tubes bring to the table is the ability to build a low-distortion amplifier without loop feedback. With no loop feedback, time-domain distortions are 100% eliminated. With feedback, time-domain distortions become the name of the game.

How does this discussion apply to tubes versus SS in preamps?

Aball's comment about "electron mobility being about a zillion times higher in a vacuum than in doped silicon" reminds me of something Bill Johnson once said about a signal going through a vacuum tube coming out unharmed while a signal going through a semi-conductor gets altered/harmed in various ways.

In practice when listening you can often hear that solid state equipment tends to harden and sharpen transients while closing in the ambient space of live recordings and obscuring the subtle textures of instruments. I assume that this is in part because a signal has to "fight" its way through a solid material in the case of a semi conductor and doesn't do so in a vacuum tube.

I've always intuitively felt that it's because of what Aball was referring to in his post that the sonic advantages of tubes over transistors exist even when the amplifier operates nowhere near clipping and also exist in preamplifier comparisons. IOW, there seem to be some intrinsic advantages to vacuum tubes apart from their distortion behavior.

Doesn't the signal have to fight through all that copper wire? To me there is no doubt that tubes sound better, so maybe Bill Johnson's explanation is true, yet it does seem that a signal has a long way to go from needle or laser to drivers.

This is a great thread. My personal experience as a trained musician and not a scientist is that class A has always sounded "bigger",more powerful and more accurate(I could also say "musical" but I don't like to use that term).
I remember back in the 70s hearing a (200rms) GAS Ampzilla with some Energy speakers. I wasn't moved.We then heard the same speakers with a little 10watt class A Bedini and it blew the Ampzilla away in every way. That was a learning experience that has always come back to me when I audition amps.I hear tube amps similarly to SS amps.
Could someone talk of Triode PP vs Ultralinear? Since they are frequently the same amp being able to work in either mode.

Now what I really want to know is will Ralph's M60 work with my Acoustats! (with zeros of course).

just having fun

e

Yes Pubul57, the signal does have to fight its way through all of that copper wire, but as we have learned over the last couple of decades, the dielectric is as important as the conductor and air dielectrics sound the best in cables for much the same reason that a vacuum sounds best in amplification.

The less physically intrusive dielectric there is to block and distort the signal, the better.

Well, for whatever reason, tube amps sound better to me, and believe me I have tried several times to fall in love with an SS amp (all have been Class A)and they always end up going back and I go back to my tube amps. My speakers may have a lot to do with that, I'm sure with some SS would be the way I would have to go and tubes might not do quite so well in driving them.

Atmasphere, I would really like to read that GE report in complete form.

I've only seen snipets but its easy to prove if you have some very basic test equipment.

All you need is a sine/square wave generator, a small amp of any type, a VU meter and a speaker.

Set up the sine to drive the amp, which is in turn driving the speaker. Put the VU meter across the speaker terminals. Obviously you don't need a lot of power for this test. Set the sine wave to read 0VU on the meter. Now switch to the square wave and set it **without looking at the meter** to the same apparent sound pressure level.

What you will find is that with the square wave you are setting it somewhere in the neighborhood of -20 to -30 db to get the same sense of volume- less than 1/100th of the original power!

Square waves are composed of only odd-ordered harmonics. This is a very simple test, but it illustrates the issue very clearly.

I'd be more interested in seeing at what volumes, ratios, and correlations are involved vis a vis the parameters in which the devices would be used in actual practice and what the rates of responses were and what they were compared to and against. Outside of that, the snippets might very well be taken out of context.

Unsound, seriously, just try the test I outlined above. It will eliminate any doubts you may have. When GE did their tests they found that people would not object to up to 30% THD- if it was all 2nd harmonic. But less than 0.1% of odd orders and they objected quite a lot.

Atmasphere, I don't have that kind of equipment. It's not that I doubt you personally, it just appears as though it might be out of context.

Unsound, its not. Almost any service shop would have such gear though, you could easily set up this test at almost any one of them simply because the speaker and the amp really are of no consequence in the test- the results are that profound.

How the human ear detects volume is a fundamental rule of human hearing- the 5th, 7th and 9th harmonics are the cues that tell us how loud a sound is. If these cues are distorted (enhanced) even by slight amounts, we hear it. Bright, hard, sheen, clinical, brittle, etc. are all words that audiophiles use to describe enhancement of these harmonics by very slight amounts; 1/100th of a percent is easily heard.

I wonder if GE performed these tests to determine how airline passengers would react to their jet engines noise inside the airplane. I know that flying is so much easier with noise canceling headphones;the noise is very fatiguing.

just a thought

e

Atmasphere, that might be true, but then there is the issue of whether or not ss or tubes offers such a distortion in the first place, whether or not it does, does it do it often enough or at enough volume to be noticed, whether or not the effect is masked, enhanced or not effected by what proceeds it, follows it or accompanies it, and what by what ratios? Is it lost in the mass of other distortions?
If ss is more prone to such distortions, wouldn't ss sound louder at lower volumes? Isn't that exactly the opposite of what some here are claiming, that tubes sound louder despite lower power outputs? How could the speaker and amp be of no consequence? With all due respect there are way too many things to consider before taking such an excerpt at face value.

Unsound, sounds like right here is the point where you are going to have to try this out yourself rather than relying on other's input. I've only been offering the 'why' behind the experience.

This is strictly my opinion/impressions

Having owned some SS amps SUMO, PS Audio, Hafler, ML33, ML 33h, ASR Emitter II over the past 20 years I have made a switch to tubes. Have settled for a 211 SET and am really enjoying it. Its 18 watts of pure bliss.
Friend brought over his VIVA mono's as well as his MACTONE.
The Viva's were great and the Mactone was nice at lower volumes.
Do most of my listening around 75 to 85 db, above 95 getting a little loud for me
For me the music that comes through the tubes is much more involving. In my case anyways.
Was really curious on having a SS power house amp in with my 18 watter.
Reading HP's review, decided to try a pair of 1000 watt Brystons mono blocks.
Had them on loan for a week and they disappointed me to say the least.
This is not to say that a SS may not reside in my home but for now I am converted.

YMMV.

Atmasphere, the "why" for me is; never mind the isolated tests, why haven't I come to prefer tubes in real systems? Please forgive me for answering my own question, I suspect it might have more to do with the speakers that I seem to prefer. Whatever charms tubes have (oh yeah, I can appreciate some of them) might be outweighed by the compromises that the speakers that they need to be paired with have. In the end we listen to systems, not components, and especially not isolated tests. Of course that is not to suggest that isolated tests don't have merit, in proper context they absolutely do.

Unsound, I think you hit on it, some speakers simply need SS to be driven properly ans tube amps will not perform well with them - usually amps with low nominal input impedance, but perhaps more importantly speakers with big swings in impedance at various frequencies - I think Theil speakers might be like that. Like the question of passive versus active preamplification, the system context makes all the difference, and not necessarily the inherent attribute of the amp, preamp, or anything else.

Unsound, for your answer:
http://www.atma-sphere.com/papers/paradigm_paper2.html

Tubes will not drive all speakers 'correctly' and of course there are speakers that cannot be driven by transistors.

However I am pretty sure that this thread is assuming that the speaker in use is not a variable for the purposes of this conversation.

Atmasphere, thank you. I read the link again, it's a good read and worth re-reading. The link points to feedback as the anathema to good sound. I tend to agree with that, but, as the link suggests the lack of feedback is not exclusive to tubes, and doesn't suggest to the amount of feedback that becomes objectionable and/or might provide an appropriate balance of pros to compensate for the cons.
Perhaps better for another thread, but, I could imagine a digital processing ss amplifier that could use feedback and then correct for the time lag.
While the OP's speakers might seem to be better suited to tube amps, I think the blanket promotion of the notion that lower powered tube amps sound louder than lower powered ss amps is misleading, and furthermore that the premise of choosing a system around amplification is misguided. You of course, may disagree.

Unsound, well, not vehemently at least :)

All the things I have looked at in the last 35 years or so point to tubes more closely obeying the rules of human hearing than transistors, mostly due to better linearity. So for the most part, I would build a system around the amplification, and look for a speaker that matches, rather than the other way 'round. It seems to me that this is an easier path to a system that sounds like real music.

Atmasphere,

What speakers cannot be driven by SS and why?

Thanks!

Is there such a thing? Seems like SS can drive anything, it just won't sound as good as tubes with speakers that can be driven effectively by tubes.

Atmasphere, it's exactly here where we diverge. IME, speakers both objectively and subjectively vary more than other components, and have a more varied response in different rooms/setups. With that said, all the speakers I seem to prefer, work best with ss. It seems to me that speakers that work best with tubes, do so with that intention, and seem to suffer much greater compromises in order to do so. IMHO, those compromises swamp what ever advantages tubes might(?)offer. With that said, it would seem to me that the easiest path to a system that sounds like real music is to build a system around the constraints we have the least control of; budget/room, and the speakers which adapt to those variables more so than any other components, and to their more varied unique voices to which our own unique specific sensitivities must adapt to more so than with any other components. YMMV :-).

Mapman, Pubul57, it would seem to me that speakers with a benign phase angle and a higher impedance rating might be better served with tube amplification over ss amplification, that would loose power with an increasing impedance rating.

Here are some speakers that are not well driven by transistors: ESLs (too bright, no bass unless the speaker is only a foot or two from the wall), horns (usually very shrill, due to the reactive nature of the drivers), full-range high efficiency drivers (similar to horns), any box speaker wherein the designer was expecting a power response from the amplifier rather than a voltage response.

An example of the latter is the Wilson Watt/Puppy, which had a resonance in the tweeter. This was controlled by a trap filter set at the frequency of the resonance. This caused a 2 ohm impedance at that frequency (2KHz). Tube amps, encountering that impedance, do not make much power and everything is good. Transistors dump power into that load, resulting in brightness. This is why you see such conflicting opinion on that speaker.

for more info see:
http://www.atma-sphere.com/papers/paradigm_paper2.html

So IME, since I prefer the reduced coloration of tubes, it makes sense to me to choose a speaker that works with that, rather than one that requires a transistor amp to sound right. IOW, that's why you choose the amplification first, then the speaker. Otherwise you can flush some big money down the loo.

Atmasphere,

Interesting.

Does Wilson then state that the Watt/Puppy was designed to work best with tube amps, or is that just the way it happened to turn out.

If not, then it sounds more like the Wilson design is flawed however a tube amp might be the right bandage.

Interesting conversations. The original conversations changed from the definition of power to sound quality of tube vs. solid state amps. There is an amazing bias here between the tube lovers and solid state lovers and music lovers. Personally, if the music doesn't sound real, then I couldn't care less if it is solid state or tube. Same logic applies if the sound drives me out of the room. As I mentioned previously, quality designed tube or solid state amps would reproduce the signal accurately and both sound wonderful. Speakers have various impedances and some are easlier to drive than others and that really affects whether the amps would work well or not. There are many various criteria for amp design. Imput impedance, gain, output impedance, current capacity, voltage, power output into specific loads, etc. All of these criteria can help determine if the design and construction and parts used should be of higher quality or not. Some times, more than not, you really do get what you pay for. All that said, I have listened to some wonderful tube equipment and also have listened to some equally wonderful solid state equipment. Nothing is perfect yet. it would be hard to design and build perfect. First, you have to assume that the music was recorded 100% correctly, using equally great recording equipment and that just simply is not the case. Maybe with Mark Levinson or Manley recording gear, but in most cases, the music isn't recorded perfectly from the beginning. Then send the signal from a source (album or cd or tape) to your preamp. Well, the cables have impedance don't forget and will slightly degrade the signal, unless corrected for. the pre-amp will degrade the signal. not one is perfect. The cables from the pre-amp to the amp degrade the signal. The amp will degrade and the speakers aren't perfect in reproducing signals either. See where I'm going? At this point in our scientific history, we aren't there yet. Electricity over wires and through tubes, resistors, inductors, capacitors, transformers, etc. will produce distortions and have losses. Can't get around it. Can a tube amp beat a solid state amp? absolutely, same can be said visa versa. How were they designed and built? Were they designed and built on the same price point? power output?, etc. if not, you are comparing apples to oranges.

I love good, accurately reproduced music and couln'd care less if it came from tubes or solid state. If it is right, then it is right.

enjoy

Atmasphere, I suspect that some like; Jim Strickand of Acoustat, Roger Sanders of Sanders Sound Systems (formerly Innersound), Roger West of Sound Lab, Gayle Sanders of Martin Logan, Nelson Pass of First Watt, and Dave Wilson of Wilson Audio might disagree with your proclamation re: the suitability of ss with the types of speakers you've mentioned.
Some would argue that it's actually the additional coloration of tubes that make them appealing.
I would argue that there is greater chance of flushing money down the loo by prioritizing speaker choice to accommodate amplification rather than choosing a speaker which fits in ones budget, works in ones room, and which offer the least objectionable coloration's for the individual purchasing them.

Unsound, if they disagree, its only because they have not been studying what happens that is different between tubes and transistors with respect to how they drive a load. Roger Sanders and I already went around on this one, and if you ask Roger West, he'll tell you that a lot of his customers use our amps... and Nelson Pass has different nomenclature as he uses Voltage Paradigm terms and I don't, but he and I are on the same page here. Just look at his articles about 'current source' amplifiers.

You might also look at a great article written by the chief engineer of EV http://paulspeltz.com/tomcik/index.html

What you get from this article is that there are no known examples of speakers needing over 20:1 damping factors, but that there are speakers that need damping factors of 0.1:1. IOW, the Voltage Paradigm does not work for all drivers.

Sorry for the OT- this really deserves a different thread.

Atmasphere, I do believe your argument has merit. It's just interesting that a couple of those ESL designers also designed ss amps to be used with them. Nelson Pass used ESL's amongst others when developing the Threshold amps. J. Gordon Holt, founder of Stereophile used both tubes and ss with his ESL's. Many of the others used both tubes and ss when demonstrating their speakers at big shows. I would imagine they would want to demonstrate them at their best, and at the very least, not at their worst. I'm sure many who can afford them, use your fine amps where appropriate.
The damping factor issue is a whole new ball of wax, and yes, your probably right, better for a different thread.

Unsound, you are right, a lot of ESL designers do work with solid state. I am of the opinion that they have a particular challenge- break out of the niche that they are in by coming up with an ESL that actually works with transistors...

The problem is two-fold. First, the impedance decreases as frequency increases, meaning that a transistor amp will make more power, causing brightness. Bass is an issue, as there can be some pronounced impedance peaks in the impedance curve. This prevents a transistor amp from making power. This is why a 200 watt tube amp can keep up with a 600 watt transistor amp on a set of Sound Labs, as the 600 watt amp may only be able to make 75 watts in the bass, where the tube amp can be capable of nearly full power.

The second is of course that the impedance curve has nothing to do with driver or box resonance, something that is fundamental to the operation of the Voltage Paradigm. In fact ESLs prefer to see flat power response out of the amp rather than flat voltage response.

To limit these issues a lot of ESL guys keep the speaker impedance very low- 4 ohms in the bass and 0.5 ohms at 20KHz is common. You still have the 8:1 change in impedance, but many transistor amps cannot make much in the way of additional power into 0.5 ohms and at that impedance, the speaker cable itself is a huge limiting factor. Its a band-aid approach, and when you see this its an ESL manufacturer that wants to cash in on the extra market share that they see in transistors.

You may have noticed that this is an entirely different example of how a tube amp with less power can be more powerful than a transistor amp; whenever you are dealing with high impedances this can be the case. Sound Labs have a peak of over 40 ohms in the bass. The 600-watt transistor amp above driving that peak might only make 75-100 watts.

Atmasphere wrote: "What tubes bring to the table is the ability to build a low-distortion amplifier without loop feedback. With no loop feedback, time-domain distortions are 100% eliminated. With feedback, time-domain distortions become the name of the game."

My understanding is that the reason time-domain distortions are of audible significance has to do with the human auditory system. The ear has a characterstic called "masking" by which it ignores a low-level signal that is near (in frequency) to a high-level signal. Audio data compression algorithms (such as MP-3) take advantage of this and simply omit signals that would likely be "masked".

Masking works great in the frequency domain, but guess what - it fails miserably in the time domain! Unless the loud and soft signal happen at exactly the same time, the soft signal is not masked. Distortions that arrive slightly later in time, even if they are much lower in amplitidue, are far more audible than the same distortion which arrives simultaneously with a masking signal.

Duke

Atamasphere, again I think your argument is sound, but, once again, it's interesting that for example, that J. Gordon Holt found the 160 WPC ss Threshold SA 1's to have better bass than the 225 WPC tube VTL 225's on his Sound Labs.

Duke, perhaps a bit off topic, but in a previous thread Atmasphere offered a link to a 55 year old paper by a speaker manufacturer's engineer that within the context of that paper, regularly suggests the use of feedback to provide appropriate critical damping factor. Most of the speakers referenced in that article appear to be of higher impedance i.e. 16 Ohms, which I suppose was typical of the times, as was probably the limited availability of high powered amplifiers. While I generally agree with the thinking behind not using feedback and IME the proof is there in the listening. My point being, that it might be hard to have and use absolutes in designing audio gear. There often seems to be a need for appropriate trade off to make the best complete package.

Unsound, amplifier/speaker synergy can definitely be used to advantage. This is how it's done with a high output impedance amp: The speaker designer uses impedance peaks to get the amp to deliver more power where he wants it. We almost always see impedance peaks in the bass region, so by playing with the enclosures's tuning frequency the designer can use those impedance peaks to extend the bass deeper than it otherwise would have gone. However if the amp's output impedance is too high, the bass will boom no matter what the tuning - so there is an "optimum" for a given speaker.

The reason this type of amp doesn't give good results with all speakers involves more than just the bass region. The speaker's impedance curve usually has peaks and valleys above the bass region, and a high output impedance (or current-source approximating) amp will tend to deliver more power into the peaks and less power into the valleys. A low output impedance (voltage source approximating) amp does the opposite. If a speaker has a smooth impedance curve above the bass region it can work well with both types, provided the bass tuning is adjusted accordingly. With Ralph's S-30, most of my speakers will exhibit roughly one-third to one-half octave greater bass extension than with a solid state amp, but I have to change the tuning frequency. That extra bass is pretty much a "free lunch". In practice I would say Ralph's amps are closer to a "constant-power source" rather than a "constant-current source", but that's still different enough from "constant voltage" to present unique challenges and opportunites for the speaker designer.

Now a designer can also take advantage of the "free lunch" to be had from a solid state amp, by dropping the impedance in the region where he needs more output. In that case, I'd parallel a second woofer in the bass region to drop the nominal impedance to 4 ohms, increasing the amp's output in that region. That calls for a second woofer and a larger enclosure, so it's maybe not as much of a "free lunch" as the first case.

Duke

Unsound; I think you are referring to the GE study in the 60's. I found the paper to be very imformative AND unbias, as you seem not to be. I have been a SS person my entire 53+ yrs. I will say after hearing a properly set up tube system I desided to sell my SS and give it a try. There are no absolutes only trade offs. BUT there is no denying tubes. that would be like denying jitter in cd's just because they are only 1's and 0's. Oh they did!

Duke, Ralph, Unsound, thank you for the dialogue - very interesting indeed.

Duke, thanks, that all appears to make sense to me. I do have further questions, but I believe they are not germane to this thread.

Koegs, actually I was referring to more recent post by Atmasphere, where he offered this link:
http://paulspeltz.com/tomcik/index.html
I don't believe there is any bias in this report.
It is interesting that in the link Atmasphere offers, the writer suggests using feedback to achieve critical damping factor, when Atmasphere has gone on record regarding his objection to the use of negative feedback.

Speaking of damping, don't drivers in speakers have their own damping where some drivers need more damping and others less, so that they don't need, or want, to much damping from an amp. For instance, my Merlins are said to have critically damped (whatever that means) damping and therefore work best with tubes and tended in the past to not do so well with SS as they overdamped the speaker.

For instance, my Merlins are said to have critically damped (whatever that means)

Critically damped means a Q of 0.707. It is a function of the driver Qes (electrical Q) and Qms (Mechanical Q) and the acoustic damping from the box (air pressure).

A design that is overall critically damped is the fastest design that returns to the rest or "zero" position without overshooting the rest position when the power is removed.

Shadorne, well done.
The link Atamasphere provided is really worth a look.

Koegz, I read that paper some years back, but I have not seen it on the web. Do you know of a link to it?

I do not.

04-10-10: Unsound
Shadorne, well done.
The link Atamasphere provided is really worth a look.

Thanks - yes it was very interesting and useful. Please bear in mind that all the experimental results were for "infinite baffles" (no box).

The acoustic suspension is usually the most powerful damping force in a box speaker (until you get below the port resonance in a ported design when it begins to behave like an infinite baffle). This controls whether the speaker will sound "boomy" (underdamped) or "tight" (critically damped) over the designs resonant frequency. In practice it is rare to find a design that is overdamped.

In infinite baffles the amplifier damping along with Qes becomes the dominant factor...and in this case the match with the amplifier is indeed critical as the amp can control the overall system Q to a large degree - to the good or the detriment of the sound.