Tube power vs Solid state power, how much is enoug

Thinking about getting into tubes. My concern is how much is enough? From what I've seen, tube amp power is, on the whole, lower than solid state. I mean - ain't watts, watts? It's sort of confusing. Not being a big fan of non-dynamic (plannar, which there is nothing wrong with them, just not my cup of tea)speakers, I aim to wind up with either BW802, Legacy Focus/whispers, or the like. Unless I can find another way to achieve full range sound with a tube anp, I'll probably use(and really want to), my Krell with the tube, in a two amp configuration, driving one pair of the above mentioned units.

Shouldn't manufacturers just state voltage development or current ratings, instead of watts? Sure, more folks recognize the term watts, as it relates to power. But if it all comes down to how much voltage/current can be developed, and how quickly, then the term "watts", seems arbitrary. More so wehn you talk about "tube amps".

For the most part, I've long since quit looking at specs and just let my ears do the judging. That seems the best route. Problem with that is my ears usually end up arguing with my wallet, heart, and what is left of my brain. Some of these arguments are frightful. The winner is not always the ears. More times than not, the wallet wins. (not always), but usually. I try to leave the brain out of it as much as possible. Although, in this instance, I need to throw the brain a bone so I ask this question.

Just how do you figure out tube watts vs. solid state?

Please help my poor, ignored, seldom the winner, brain.

the brain
I will try to be as politically correct as possible here... :)
In my opinion, 100% of technical information provided with audio equipment is not meaningful as far as describing sound. In my experience the only way to solve this problem is to try specific components together. My current speakers are driven by 25 tube Watts currently with beautiful results. Before that they were driven by over 100 solid state Watts to my complete dissatisfaction.
The basic deal is about half the tube watts vs SS watts for control/Clipping on the speakers. If your speakers Clip at 100w with a strong SS amp(not cheezy piece), you can figure clipping at about the same output with a 50watt tube amp, or thereabouts.
Meaning you can get away with half the tube watts you normally need with SS before clipping sets in, from my experiences. The reason is that tubes are more forgiving and rounded off at the extremes. SS amps go into hard clipping, and are not forgiving. Not exactly sure how to explain that correctly.
Either way, you can get into more distortion with a tube amp, and not clip/damage the speakers. If you used to use a 100watt amp. I like to think you can get nto a 50watt tube amp and be fine....if your speakers are good with those numbers sensitivity-wise for overall output/volume
You're looking at it backwards. It's not how much power is enough but how efficient the speakers are to produce the volume level you want. A highly efficient speaker, say 101 db per one watt/meter, will blast eardrums with only a couple of watts of power whereas a 86 db @ 2.8 V-m speaker will require a couple of hundred watts to be at the same level. It's like saying: how fast can I go with a 160hp engine - if it's on a skateboard, then very fast but if it's in a bulldozer, you won't move. Power is irrelevant unless you define the load it's driving.

If you want tubes and loud, look at high efficiency speakers. If you want a speaker that's not too efficient, go with higher powered tubes or solid state. A watt is a watt - but what a speaker does with it varies from make to make.
Tube amps tend to clip 'softer' than SS amps. That is why you can play a tube amp as loud as a larger SS amp. Look at the distortion specs of both amps at full power and also the spectrum of that distortion. Generally the SS amps will come on strong with higher order odd harmonic components as they exceed full power. Tube amps generally have more harmonic distortion; but it builds more slowly and tends to be dominated by 2nd order even components. These are present in musical instraments and generally don't sound harsh or displeasing to the ear. Also, since they are already there in the music, it takes more for the ear to notice the increase. Whereas the higher order odd components tend to stand out and sound bad.
A watt ain't a watt ain't a watt. This is true even though it is supposed to be and there are set electrical parameters as to what constitutes a "watt".

Tubes and SS devices work on different principles. To put it in plain English, almost all SS designs are voltage limited whereas Tube amps are current limited. Some designs will work better with one type of amplification whereas that same amplifier may be completely lacking with a different type of speaker load.

I can explain why this is so if you folks are interested. Sean
I have very high efficiency speakers and there is more to it than that. Tubes generally fair better with a higher resistance load and are less prone to distort (impedance matching). Secondly the dynamics of the music change the load as you play and how loud you want to play changes the tendency for audible distortion. I have found that certain drivers within a speaker respond differently despite a nominal load as well. If your speakers have power-hungry woofers beware. Finally you should be very clear the power as stated in RMS wpc tells you only a small part of what an amps overall "power" is. The current capacity is very important. Since I am not an electrical engineer I can't tell you all you need to know, your ultimate test is to listen. Therefore Blindjim your choice of speaker and amp in combination is critically important. I use a 40wpc tube amp on lower 88db/W/M efficiency speakers (beauty) and a true 100 wpc solid state on very high efficiency speakers (beast) and get the effect I want from those two systems.
Sean, please do.
Sean is right and Sean is wrong. A watt is indeed a watt. Also, many years ago the Federal Trade Commission regulated the way manufacturers rated the power of their consumer audio equipment, so generally, one at least gets the "100 watts into 8 ohms from 20 Hz to 20KHz at no more than 0.1% harmonic distortion" kind of rating. (Previously manufacturers rated amplifier power any way they wanted and usually they didn't tell you enough.)

However, Sean is correct about tubed and solidstate amplifiers behaving much differently driving different loads. Because tubed amps have output transformers, they have relatively high output impedance, while SS amps generally have very low output impedance. Within its construction limits, a SS amplifier will continue to increase its current output and maintain its voltage output (hence increasing its power) as the load impedance decreases. This means that about-any SS amp that's driving 1 watt into 8 ohms will drive 2 watts in 4 ohms, 4 watts into 2, 8 watts into 1, 16 watts into 1/2 ohm, etc. Of course, the higher amount of power (and current) we start this exercise with, the quicker the amp will reach its limitation on current flow. 'High current' amps will indeed increase power as the load impedance decreases, and the good ones will double rated power at least once. For instance, an inexpensive amp may have only one power rating, usually into 8 ohms. If it doesn't have another rating of higher power into 4 ohms, it’s not a high-current amp IMO. Some will have more power at 4 ohms but not double the 8-ohm rating. The better amp will indeed double its power into 4 ohms, and the really high-current designs will double again into 2 ohms. For example, my humble little (but HOT-running) Lazarus hybrid amp (with SS output stage), is rated at 50 watts per channel into 8, 100pc into 4, and 200pc into 2 ohms. It costs lots more money to design and build an amplifier that will do this.

Tubed amps can't do that. A tubed amp will increase power slightly as load impedance decreases but not by much.

But still, a tubed amp will sound somewhat better when driven to deliver power beyond its rating (ie, ‘at clipping’) than a SS amp will; many people say that a tubed amp clips more ‘gracefully’. That’s why many of us say that generally one can get away with a tubed amp of half the rated power compared with a SS amp. However, the lower the impedance of the speaker (and hence the more current the amp has to dump into it to play music as loudly as the listener desires), the less likely would a tubed amp be able to cope gracefully and sound good. Of course, each amp of either type will behave differently and sound different under various real speaker loads.

Also, Gs5556 is absolutely correct, and lots of us pay little attention to the relative efficiencies (sensitivities) of speakers. Every 3dB of higher or lower sensitivity requires double or half the power to drive to equal loudness. My 96dB-rated Kindel PLS-As require ONE-QUARTER the amplifier power than a 90dB-rated speaker to drive to equal loudness. That’s why my ‘little’ 50wpc Lazarus amp will drive them to deafening levels. I don’t wish to belabor this point, but a not-untypical 87dB-rated speaker requires FOUR-HUNDRED watts to generate the same loudness as my 96dB/50-watt combination.

So Blindjim, start your evaluation process by picking the speakers first, understanding their sensitivity ratings, and then picking some amplifiers to listen to. Unless the speakers’ impedance dips below, say, 4 ohms over a significant part of the frequency range, a tubed amp will probably do very well.

And my answer your original question is 'enough to avoid amplifier clipping about 99% of the time'. Yes, that's not very useful, but YOU have to answer it, not us. :-)
Thanks Jeff

Now, for the next hurdle. Matching amps.

I want to run SS on the bottom and a tube, on top. Go figure. (primarily because I have SS, I like already - just need a tube.)

It's been pointyed out to me recently to get a match "look at the output voltages of the amps. Final output? Primary? In between?

Gonna use both of them to run B&W 03 or 02's with.

Any suggestions B&W is pretty sketchy about this, as they rate impedance somewhat differently than most.
I owned a pair of B&W 802 Matrix III's for several years. Amplifier power ratings aside, solid state amps control woofers on power hungry, moderately large loudspeakers such as the 802's better than their tube equivelants. I drove my B&W's with a Threshold T-200 SS amp very nicely. I too toyed with the idea of changing to a tube amp and after a dealer listening session using a tube amp rated at 80 watts / channel, it was instantly clear that although there was much to admire about the overall qualities of the tubes, the woofers in the B&W's were soft and unfocused compared to use with my Threshold. The best situation for someone who cannot afford or does not have the room for a powerful tube amp - they are big! - I recommend a tube preamp and a solid state amp which will give you the tube sound you desire with the bass control necessary for best enjoyment.
I own a pair of the original ATC SCM 10 passive and they're 80db (I have not seen anything lower) speakers and extreme power hungry as expected. I used a krell fb300 (300Watt) and it sounded grainy and harsh. I then switched to Mac MC240 (55Watt) and it sounded warm and sweet but not as dynamic. I then switched to Lafayette KT-550 (60Watt) and it is the best match I ever heard coming out from these speakers with warm, sweet and dynamic. Just like the SS gear, not all tube gear are created equal. Don't just truss power ratings because you have no idea how it was measured.
Well, all the comments have merit. I do appreciate them greatly. Thank you.

Learned a lot since I opened this thread. some startling things as well. Like just how much power is actually running the speakers at any given time. Usually less than 20 watts. Also, just how much better good tube amps sound than similarly priced solids.

Hence I am sold on the idea to bi amp. two reasons.

One - don't have to lose my existing solid state amp.
Two - get to enjoy fuller sweeter, more rounded and life like music. That's the ticket, right?

Now just which tube AMP (S)? And which tubes in the tube amp to use? pUSH PULL, FEEDBACK, SELF BIASING, CATHODE FOLLOWER. . . . mAN! wHAT A BUNCH OF STUFF TO DEAL WITH.


Any suggestions, apart from the Laffeyett? Used or new?

Thanks to all.
I have a Jadis 40 watt intergrated Orchestra Reference, has 4 KT90's. I just built a pr of Seas' Thor's, rated 87db, that is extremely low. The little Jadis has no problem, provided the treble and bass tone controls are given a little boost. Results, Rich bass, clean(no bark) mids, no frothy or "fake" highs. Thus tubes can drive super low sensitive speakers. Provided its a good tube amp. In contrary the big 100 watt Rotel ss amp, 981, sounds like pure Class Grabage on the Thors.

Just having picked up a pair of Klipsch RF7's I think this thread is great.
The choices for an amp seem endless......
Blindjim, what'd you end up doing?
My 2 cents (like anybody asked...)?

Trying to get disparate amplifier technologies to get along in the same system is challenging to say the least. You'll need some sort of electronic crossover, which is an additional (and audible) building block, and rarely has the correct crossver curves that a passive crossover does. So that will be a real challenge.

The speakers you listed are not that unfriendly to tubes, but beware the B&Ws that list nominal impedance at 8 ohms then wind up actully being 4 ohms in the woofer region, where most of the amplifier power is demanded. Not a good combo for a tube amplifier! The 802 is an example of such a speaker.

I strongly recommend that for any tube amplifier that you choose, contact the manufacturer and see what their experiences with the speaker you choose is. They may have some tips for you.

I also stongly advise you to heed this tip: try and get a speaker that is as efficient as possible! This was mentioned earlier in this thread and the value of this cannot be understated. If you choose a speaker that is 95db, it will require an amplifier of 1/4 the power to be as loud as a given combo with a speaker of 89db. Tube power in particular is difficult to make! So where a speaker of 89 db might need 200 watts in most rooms (I have found that to be the minimum in my room with such a speaker), you will find it much easier to find a musical tube amplifier if you only need 50 watts to make the speakers sing. In 200 watt amps, you can count the ones that actually sound like real music on one hand, and have a finger or two left over (there are no musical transistor amps, BTW...). But at 50 watts its a different story.

So be careful. Otherwise stand ready at the toilet to flush those dollars goodbye.
blindjim, your last post hit on an important point controlling output and that would be amp design details. Especially class a/b verses pure class a. For the audio rig i have VTL mb185s which are rated at 230 w/side running on 6550 tubes. My guitar rig is a boutique 35 wt el84 class A rig. The guitar amp is insanely loud. It will smoke 50 watt el 34 and 6550 based amps (ok that ain't a real big difference because to double spl you need to 10x output) and hangs perfectly with larger amps and the home rig. A lot of that is in how the amp is voiced as cuts like a knife where as a home rig will be voiced more least you'd hope so.

Without sliding too far off field here, I'm curious as to the point where a speaker's high rated sensitivity is undermined by other criterea.

For instance, the Athena AF-2 is rated at 93db and sells for $600 a pair. Wouldn't these speakers do well handling 40W to 50W per channel tube amps?
93 db is a medium efficiency, not high. High would be over 100db. Plus you have to factor something else when you use the word 'senstivity'. It is NOT the same as efficiency.

The Senstivity spec is 2.83 volts measured at the speaker terminal and the sound pressure measured at one meter on axis.
Efficiency is the same, but measured with 1 watt at the speaker terminals.

If the speaker is 8 ohms, the two numbers are the same. If the speaker is 4 ohms though, now the actual efficiency is 3 db less! This is because 2.83 volts driving a 4 ohm load works out to 2 watts, not 1. All of a sudden 40-50 watts may not be enough!

I don't think the cost of the speaker plays a role here, although obviously if you are investing in a tube amplifier it only seems reasonable to use a speaker that allows the amplifier to perform in its best light...
Thank you. Everybody. I'm a bit late in responding to this line of thoughts and experiences, but I do thank you all.

I've chosen what I think is best for me.... tubed preamp, and Solid state amp. Seems the logical choice with fair benefits over strickly SS all the way. Not to mention the greater assortment of loudspeakers that are made available by virtue of the SS amp. I do love the combo I have now. When with speakers not known for their "Audiofool" (and yes, I'm including myself there too)qualities, but far more than adequate, colorless and homogenously coherent speakers... the sound I have is absolutely liquid. Detail, sweet, warm, rich all of these apply.... a good source as well adds to the mix... got one of those too. Finally.

Presently, I reside in the realm of "Man, that's really good!" everytime I turn it on and play it, now. of course, I would prefer to be in the court of "Man, that's really great." each time I play it, though.... and hence the quest for a bit more something edges me onward. Upward. More to the point, to the arena of "Man You sure must have more dollars than sense." which is where I would need to be to acquire the items on my wish list. Not necessarily the item one needs to obtain great audio but close to that , "...great!" sounding ball park. As evidenced by the current state of affairs I enjoy. I am not insatiable. I do have limits. I can be happy simply with the sound that continues to present itself as fresh, involving and musical at each sitting. I am certain also, that domain is soon to be one I enjoy routinely.... a few more peripherals, wires, and an upgrade in loudspeakers will, I am sure, do the trick.

So thanks again for your experience and wisdom, and interesting insights. Perhaps one day given my taste in sound, I'll go ALL tube.... for the time being with an amp of very good quality and less than two years old, I shall remain in this not uncommon space where glass and transistors, give voice to a most wonderful song.
Can I raise another can of worms, after this excellent thread seems to have come to a natural conclusion. Most people agree there is a difference between tube and SS watts, possibly related to the tube amps prediliction for "soft clipping", but what about the difference between the watts in different tube applications? It's my impression there are clear differences, going beyond the Class A, A/B question. Am I right in saying Push/Pull has less grunt than SET for example and output tube choice is critical too, maybe EL34, less than 300B, in turn less than 845 or KT88. I may be way off track, but would appreciate any views. The proviso is of course, different speakers present different loads to the power amp and so produce different apparent volume levels.
I am sitting firmly on the fences when it comes to tube vs. transistor.

Of the many tube amps I've owned, I've yet to find one that is completely satisfying in the bass. The best ones gave me good bass without the depth, tightness, and impact of the best solid-state bass. And there is quite a bit of information missing at the top end which invariably leads to a reduced sound stage. For rock and big symphonic music, ALL my tube amps were deficient in the bass and ran out of gas, even at 120 wpc!

Of the solid-state amps I've owned, none ever gave me the midrange magic of tubes. The best ss high, while extended and detailed, never rid itself completely of that last bit of hardness. NONE of my ss amps gave me the intimate, magical sound for vocals, jazz and chamber music.

So I own both types of amp and switch from tube to transistor and back frequently. I have tried ss at the bottom and tube on top with excellent but far from perfect results. While the ss bass is outstanding and the tube midrange is magical, the highest-frequency information is still missing and the sound stage is not as large as it could be.

I found that I was happiest when I matched the amp/preamp to the music I was listening to at the time. I tend to use ss amps for rock and big symphonic music. I prefer tube amps for vocals, jazz and chamber music. (NOTE: Lately, my switching amp comes close to giving me everything I always wanted: deep bass, smooth midrange, extended highs, and huge soundstage. But I still miss that caramel-coated midrange of tube. It ain't accurate but I'm hooked on it!)

The best amp for you may depend more on your musical preference than anything else. You may have sufficient power with tube unless you love rock and large symphonic sound, then only ss will do. Bi-amping with ss and tube will solve some of your problems but not all. The perfect amp is yet to be invented.

justin time is correct...even the mightiest of tube amps and the most refined ss amps won't quite do what the other can. the loudspeakers you use are still the most important thing. i have been a long time advocate of push/pull tube amps, trying to have it all so-to-speak. i was recently given a tiny revox integrated which pretty much equalled my reference gear in every way except that 'front to back' depth that tubes do so well. tonally though, it is an equal to an amp that cost almost 5 times as much. the distain many tube enthusiasts have for ss gear is more emotional than reality based. your software(cd's, vinyl), your loudspeakers, and your room are- at the end of the day- are more important for the long haul
I was running 2 McIntosh MC-162's in mono (320wpc) and decided to try tubes. I bought a pair of Antique Sound Labs wave 8 monos here on Agon and holy cow!!! I was running them through B&W 604 s3's by the way, the little 8 watt tube amps (to me) actually sounded better. in the end, in my opinion, it all depends on what your going to listen to. for vocals and Jazz, clasical tubes are the way to go, but if you have those days where you have to blast some Metallica there is nothing like solid state.