How do tube Watts compare to SS Watts?

I have Theil 2.2 speakers, which have a low sensitivity (86dB), but I would like to get an intergrated tube amp. Or even all tube. But I don't know how many tube Watts I'll need to drive the Theils. My guesstimate is @ 50wpc for intergrated tube amps, but that could be wildly off. Are their mathematical conversion formulas? Second, if there is a rough range, might you be kind enough to suggest a few worthy candidates that, wheather new or pre-listened, are under $1,000 USD (e.g., Cayin model xxx). Thank you most kindly.
Mathematical formula is as follows...
Tube watts = (SS watts) X 1
Your real question should be "Can I drive my Theil 2.2's with a modest sized tube amp?"

There is a great deal of interaction between an amp and a speaker. A speaker with minimal impedence drooping to or below 4 ohms are not good candidates for anything much less than a high power tube amp. A speaker with an impedence curve that has big swings (as opposed to being relatively flat) may not be good with most any tube amp.

But apart from that, assuming that your speakers are any easy load with an 86db efficiency I'd want at least 80 watts with tubes and 100 to 200 with most SS unless they were really high current amps.

Watts are watts. Tubes sound better than SS when they clip and its more subtractive. SS just sounds crappy when they clip.
The amplifier power will also depend on the room size, and your listning position distance from the speakers.

I use a PrimaLuna Prologue 2 ( 45 Watts KT-88 Valve Integrated, close to US $ 1K ).

Speakers are Sonus Fabor Extremas. Same sensitivity as your speakers.

Room size is approx 30 feet x 15 feet x 12 feet height.

Speakers & listning position is accross the width ( 15 feet ) of the room, not the length.

My listning position is approx 10 feet from the speakers.

I get good volume ( my gusstimate is 103 dB ) before the the amp runs out of steam.

I would HIGHLY recommend the PrimaLuna Prologue-2 if you listen to Rock and Jazz. The Prologue 1 with EL-34 valves is probably better for classical.

Hope this helps.

The size of the room factors into it as well as the impedence curves that Newbee mentions. Looking at the Stereophile measurements, the impedence curve of your 2.2's is relatively flat, but a lowish 4 ohm load (3.5 min, 5.2 ohm max).
I would think that you may get by with a 50-100 wpc tube amp in a smaller room.
Overall though, I think you would be better served with a tube preamp and a SS amp, or a SS integrated amp.

Watts are watts, and I second Newbee's comment that tube amps will clip more gracefully.
I have used a pair of Wright Sound WPA 3.5 single-ended triodes with Thiel 3.6's. That's a whopping 4 watts into a 6 ohm, 86 db per 2.83V/m speaker. While it doesn't do justice to orchestral, opera or rock, it certainly played loud enough in a 27 X 16 room with classical (chamber, solo, instrumental and voice) and jazz.

Your mileage may vary depending on your room, what your sources do and what you consider adequate playback volume.
I powered a pair of Vandersteen Model 3 speakers with Quicksilver tube M-60 amps ( rated at 60 watts ) During that time I did a demo with a CJ MF2300 ( rated at 200 watts ) I could not hear a significant difference other than a bit more bass. I was under the influence that when comparing watts " tubes to ss " you doubled the rating for tubes.

60 watts tubes would be equal to 120 watts ss.

I would say that 80-120 watts would be necessary in your case though.
Rascal, the most important factor when using a tube amplifier to drive speakers, is that the speakers must have a benign impedance curve. If the speakers have an impedance curve that varies significantly, even a 1000-watt tube amp will have problems driving them. The nominal impedance numbers i.e. 4 ohm or 8 ohm is not really important as most tube amps have 4ohm and 8ohm output taps.

In short, if your Thiels do not have a benign impedance curve, go solid state.

I drive 88db speakers to very loud levels with a 12wpc amplifier, so in theory you should be able to do the same with and amplifier rated around 20wpc. Again I repeat, this will hold only if your speaker has a benign impedance curve.

There is definitely something different between the rated output of a tube amplifier and a transistor amp. Wattage is measured the same, that much is true, but anybody that has compared tube and transistor based amps of similar ratings will be well aware that the vacuum tube amplifier can produce much higher SP levels before overloading is detected.

This is partially due to the fact that tube amplifier clip in a harmonic (musical) fashion, while high NFB used in transistor amps make them square off the signal when clipping. This squaring off of the overload is very noticeable and objectionable. As such, transistor amplifiers cannot be run near their maximum rated output. Tube amplifier can.

Another theory I have heard is that naturally dispersed harmonics add to the perceived SP of the signals. Vacuum tube amplifiers tend to produce high levels of naturally dispersed near maximum output. Transistor amplifiers tend to produce unnaturally dispersed harmonics which are both very objectionable and add nothing to the perceived SP levels. Tube amplifiers therefore deliver a bit more than what their rating suggests.

Yes, a watt is a watt is a watt but the rail voltages on tube amps are much higher. In my expereience comparing tube wattage to solid state wattage it is about a 2 to 1 ratio.
I have some experience with Thiel loudspeakers - mainly with Cs 2.4. I believe that the idea to drive Thiels with tube amp is generally very bad idea. Very, very bad idea. Thiels are well known as very power hungry speakers, which provide the quality of reproduction that they are known for only when they are connected to the amp with powerful output stage. You might look at something like BAT VK-150 or similar but generally you should go for SS - and very poweful SS ...
The sound level that can be produced by a tiny amount of power was made clear to me when my son hooked up a KLH5 low efficiency speaker to his clock radio. The KLH5 was a sealed 3-way system, and the clock radio was probably good for 500 milliwatts. I told him it wouldn't work, but it did, and surprisingly well.
1 SS watt = 2+ tube watts in my experience in terms of filling a space with sound.
In my experience tubes and Thiels are a very good match you just need enough tube power to drive them and there are many factors that determine power requirements. Thiels are a demanding load but not difficult one because of the relatively low but flat impedence curve.

Watts are watts. Tubes sound better than SS when they clip and its more subtractive. SS just sounds crappy when they clip.

Some manufacturers of solid-state amps have taken this into account. Levinson amps, for example, have a built-in smoothing circuit that eliminate this harsh clipping sound when the signal gets close to the supply rails. Another that comes to mind is McIntosh, whose PowerGuard circuitry has received acclaim as an effective mean to end hard clipping.

As for the Watts question, in theory it shouldn't really matter if the amplifier is tube or solid-state, because strictly speaking 1 Watt = 1 Volt x 1 Amp. In practice, the specification is approximate, so you can expect an amp with a bigger power supply and lower impedance to sound louder with the Thiels. Also, all amplifiers differ in their "power margin" above its nominal power, depending on their circuitry details.

As a general rule, 100 Watts per channel would be a good starting point to choose an amp for the Thiels. If the brand is serious it will correctly specify its product, so you shouldn't find differences of more than 1 o 2 dB in acoustical output between a solid-state amp and a tube amp in this particular case.
Depends on the tube. SET amps with 300B, 845 are low power, "no slam" "no authority", but a midrange and highs to die for, WITH THE RIGHT SPEAKER. So scratch those off my list. ...KT88's. I heard one cheap chinese 88 and also rolled 88's in my JOR. Absoluetly no authority. Very very weak on any speaker with 90db or lower. I havea Jadis DEFY sitting on my floor waiting for a preamp, has the 6550 tube. Very very nice looking tube and should be an improvement over my KT90 Jadis OR. The seller told me has "magic". Then there is the EL34, which doesn't look too interesting. Looks like a cheap KT90. There are other SET tubes like the 2A3 (ck name?), same issues as the 300 and 845. There are a few other tubes, but these are the most used in designs. Comes down to speaker first, then amp. So only the "beefy" KT90 does the job. I'm expecting the 6550 to come through as well. These are push/pull tubes. Sorry ss amps are not "my cup of tea". None.
My jadis OR with KT90's will drive your speaker. Used, $1500. Also look at the Ming Da tube amp with KT90's/new at $900. The Cayin KT88 "might" work. But I surmise it may be a tad on the soft side. There's not many tube amps used under $1K that will offer "slam". 2 imporant factors that go into makinga great tube amp that has "punch" is the quality of trans and the quality of tubes. Neither of which come cheap. ....There are ss amps under 41K that will give some authority, but as far as fatigue factor and lack of musicality, I couldn't live with it.
I had trouble driving CS2's with Quicksilver mono amps that were rated at 60 wpc. The room was about 12 x 20 and I thought I needed tubes to make the Thiel's sound smooth and sweet but when I switched to a smaller high current SS amp they were controlled, not sloppy.

Best advice I can give is try a tube amp with some guts and use the 4 ohm taps if it has them. Or get a SS that doubles into 4 ohms.
good comments mostly. JOLIDA amps used and modified will get it done in that price. 86 db is low tho and even tho amp offers 4 ohm outputs, if your room is large and you like it loud you may need more watts. thiels do like power but i am sure tubes work fine as long as watts are there. $1000 is getting kinda thin for more than 60wpc choices imo. i use 60 wpc unit with 89 db spkrs in larger open sided room and need most of it for big stuff peaks. your room will determine much. closed rooms offer 'free' boost in spl level which can mean a lot when you have to double down power needs at higher levels. imo a watt is a watt until you get clipping. just different sound tween ss and tubes
The reason you hear a lot about tube watts being more effective somehow is due to distortion- tubes make less of the distortions that the human ear finds objectionable- and so *seem* to have a greater percentage of usable power relative to transistors.

The effect is real enough on account of the way our ears work, but if you measure sound pressure levels for the most part watts is watts.

A lot also has to do with the load, in particular tubes in general behave differently from transistors, i.e. they do not double power as impedance decreases. Often though they may *increase* power as impedance increases. Sometimes this gives you more punch on certain box speakers that have a low frequency resonance.

Bottom line is that there are a lot of variables but with many speakers you do get the impression that tube power carries more 'weight'.
>>Bartok says ....SET amps with 300B, 845 are low power, "no slam" "no authority"<<

That is sheer profundity. It's a combination of the speaker and amp, not totally dependent on the amp. I've heard plenty of SET amp/speaker combination with "slam" and "authority". Conversely, I've heard speakers that would make your amp melt down like Chernobyl.

Your statement is totally incorrect. Learn the subject matter before making such disingenuous and sweeping statements.

Thank you.
03-14-07: Eldartford "The sound level that can be produced by a tiny amount of power"

Now that I can agree with ... :-)
I stand corrected. What i mean to say is that on most speakers, SET amps, 300, 845's will not provide the current necessary to produce tension, "slam". I've had KT88's in my JOR and the result was total failure. The amp lost all its "authority". So I also place KT88's in "SET" category, even on a push/pull design. I have not heard the Cayin KT88 yet, that might change my opinion. Point is, some tubes in many designs do not offer the body in MOST speakers that a decent ss amp will offer. Put any SET amp with a Vandersteen and then put a decent ss amp. SET's will not drive the speaker. Tubes can make great music, that is IF you can find the right speaker. As you point out its a combination of the 2. Much easier done with any ss amp, tubes work only with certain speakers.
Please correct if/where I err.
after rereading above posts... i'm going further on the limb. fwiw, i think you are gonna 'need' more than 60 wpc of tubes to get 'er done. honestly i think thiels work best with lotsa juice. ss gets it done of course but you want to delve into tubes and being a convert myself i encourage others. never owned thiels but have auditioned them and they can sound kinda listless, yet defined, w/o enuf power. if you could hook them up to tubes and audition i think you would not need any of this contradictory advice. good luck! fwiw, 86 db design is a stretch in $1K 50wpc arena. personally i'd want 100wpc but your listening tastes are unknown to me
Bartok, the KT 88 (similar to 6550), etc aren't push-pull. They're pentodes. Push pull is an amp circuit config.Cheers
I thank all of your for sharing your opinions! The Theil 2.2s are presently driven by a Conrad-Johnson 80W ss amp with a C-J tube preamp. This is more than adequate for the music and volumes we enjoy. Using the ss W to tube W factor of 0.5, roughly, 40-50W tube might work; 60-75W very likely will work. I'm hoping to get something definitely warm not neutral. (I've always preferred the tone of Fritz Kreilser over that of Jascha Heifitz.) Ilooked into the Jolidas, and they are certainly impressive. But I've noticed that some folks think that they are not particularly warm or "tubey." I can't say and they are not available around here for roadtesting. Given constraints on tone, wattage, and cost, I think I'll nose around for early '60s American amps that have been, at least partly, refurbished. Or...maybe back to the Jolidas. Thanks again. Rascal
Greg, thats interesting. Not sure what a pentode is. Is the KT90 a pentode? If yes then all these 3 tubes are used in amp circuit designs that are different from SET designs using the 300 and 845 tube. Rascal, I also prefer Kreisler over Heiftz. Oistrakh was my prefered violinist, but I recently sold off his 6 cd set In Prague, oop. The set had too much romantic era stuff, which I don't care for. I love Gideon Kremer's recordings, except the Schnittke 4 vc's, which fault lies with Schnittke. Even though Schnittke is one of my top fav composers, his 4 vc's left me uninterested. Read my reviews on amazon.
Bartokfan. A pentode is a vacuum tube that has three grids, namely a control grid, a screen grid and a suppressor grid. The screen grid was added to isolated the control grid from the plate to reduce Miller effect.

A tetrode is a tube that has a control grid and screen grin (no suppressor grid). The suppressor grid is added to reduce secondary emissions from the anode.

A Triode has no screen or suppressor grid.

Triodes, Tetrodes and Pentodes can all be used in a push-pull or single ended configuration. When used in single ended configuration they all have to run class A, in push-pull they can be run in either class A or B (or combination thereof.)

Tetrodes and Pentodes have their screens grids biased to +. If you bias the screed grid from the anode, it is know as triode mode. If you bias the screen grid from a tap on the primary winding of the output transformer, it is called ultraliniar mode. If you bias the screen grid from the power supply, it is called tetrode/pentode mode.

The method of biasing the screen grid alters the character of the tube slightly. Many amps have a switch to toggle between two of these modes.

A KT90 is actually a kinkless tetrode (the KT stands for Kinkless Tetrode). I believe that is actually a pentode with the suppresser grid tied to the cathode. And EL34 is an example of a pure pentode.

Rascal52240, a Watt is a Watt is a Watt. It is a measurement. An inch on a ruler is the same as an inch on a tape measure. That said, Watts needs to be considered as part of an equation. Your Thiel's 22's have a nominal impedance of 4 Ohms and a minimum impedance of 3 Ohms. Better ss amps may double their power into that load. In your case as a matter of measurement ss Watts may be 2X more powerfull than tube amps with the same standard 8 Ohm rating. Thiel designs their cross-overs in such a manner so as to provide a steady impedance for the amp, which helps maintain steady amplitude. Some argue that, these steps drain the ultimate apparent power from the system. The point of all this is; Thiel's respond best to lots of quality power. Of course, your room and ultimate sound levels will determine just how much power you need. For many years I used the same ss c-j amp you are currently using on earlier Thiel's CS 2's. Those 2's had an easier 6 Ohm nominal, 5 Ohm minimum load. A move to a much better 250 watt amp demonstrated qualities I never new my CS 2's were capable of. Jim Thiel told me himslelf that his power recommendations were based on the standard 8 Ohm rating of quality ss amps that were capable of doubling down, and if one were to choose tube amps, one should double those power recommendations. Comparable tube power usually costs more than the same ss power. Doubling that tube power can get a bit expensive. With a budget of $1K, I'd suggest you use ss watts. Furthermore, very few integrateds have the guts to really make Thiels sing, it usually takes a dedicated power amp to get the most from Thiel's, especially when you get away from the smaller 2 ways. An old audiophile cliche' that some how seems to work more often than it should, suggests that one should double the manufactures' minimum recommendation. For your Thiel 22's that would mean 200 watts into 4 Ohms. A quality 200 watt per channel tube amp might be hard to find for under $1K. To drive your Thiels, that money may be better spent on better ss watts.
Smooth explanation, thanks. This explains why the KT88 and KT90 have different characterits in voicing. And as you know every KT90 amp will have different circuitry/ quality trans, and that also every model KT90 tube will possess somewhat different characteristic. So tubes can be a big wide open field, whereas ss amps, is "what you see is what you get" Not much can be done for a ss amp. Its all "hard wires". Great tubes can offer that much more . Tube amps with a hefty trans, can be considered an ss amp with the added benifits of musicality of tubes.
btw where do the 6550's fit in. I have a DEFY 7 sitting waiting for a preamp. Very interesting looking tube. Shorter than the KT90 but wider. Very unique looking tube. I know I will prefer it over the JOR's KT90's. The 6550 may be one of the best tubes for classiacl/orchestra. I'm betting on it. The KT90 can be a bit "raw"/"steely"/"cold", but definetly has some slam and a full midrange/good bass. The highs roll a bit. I'm guessing the 6550 kicks in more high fq's, with a "softer bass" I'll post a review whenever I get a pre, maybe next month.
>>whereas ss amps, is "what you see is what you get" Not much can be done for a ss amp. Its all "hard wires"<<

I think Nelson Pass, Hervé Delétraz, Charles Hansen, etc. etc. have proven that is quite untrue.

Thank you.
rascal, listen well to unsound advice. he has firsthand knowledge and based on my exp with jolida 60 wpc and$$$ he is right on the mark. a watt is a watt basically. thiels need POWER! an old tube amp is no more powerful than a new used tube amp. shop around awhile if you can but 60 wpc in a tube is not more than 60 watts from ss even if the ss has a rolled off clipping circuit like NAD offers. unsound has spoken with thiel himself and is really doing you a great service. 60 wpc may sound good but 100 is going to make them sound as good as they should. fwiw, in your $$$ range the sonic differences between tube amps is not as imp. as wpc in the case of driving low eff. speakers. ;)
Bartokfan, the assumptions you make pertaining to the characteristics of tube are incorrect. There are a great deal of variance is sound characteristics of any given tube from different manufacturers. A Tungsol 6550 sound very different to an Electra Harmonic 6550, which in turn sound different to SED, Svetlana or Phillips 6550s.

Additionally, factors such as the circuit design, quality of components, screen grid bias method etc. etc. have dramatic effect on the sound.

EL34 are generally known to be very melodic when run in triode mode, yet partnered with the right speakers they produces a prodigious bass slam in my V12i. KT88’s are known to have bass slam, but they are wonderfully melodic and detailed in my Audionote.

Observations on what a amplifier/tube sounds like, should be made after auditioning, not before.