Hi ...I like my solution to the same situation you have. I like the SET tone but I want to be able to use a wide selection of speaker. The answer for me was the TAD 60 power amp. It is very flexable in that it is rated at 30 watts in triod and 60 watts in UL mode using kt88 or 6550 powers tube. Using el34 , 6ca7 and the like has a little less. However the neat thing about this amp is that you can bias it into Class A and it sounds very much like an SET
104 responses Add your response
Anytime you are investing in tube amplifier technology, that investment will be best served by a speaker that is at least 8 ohms or more.
Tube amps, with rare exception, have reduced performance into four ohms.
Given that you have satisfied that part of the issue, the next is efficiency. 40 watts with a speaker that is only 86 db is not going to be a lot of power unless you happen to listen nearfield, regardless of the type of amp.
SETs in particular have certain advantages of low level detail over conventional push-pull, but to tap that advantage you will need a speaker that is a good 10 db more efficient if your amp is 40 watts! Otherwise although it might work 'OK', it certainly will not be meeting its design goals.
Bartokfan, you seem to be asking the same, albeit worded differently, question over and over. If you are doing so because you are cautious, then it is a good thing. If you do so because you dont like the responses you have been getting, it a bad thing.
I am going to disagree with Ralph on both speaker impendence and the power that is required to drive them.
A speaker with a nominal load of 4 ohm should not be a problem for a tube amp. The vast majority of tube amps will have 4 AND 8 ohm output taps, so 8 or 4 ohm rated speakers is not an issue. You simply use the appropriate tap off the back of the amp. Of course, all bets are of if your amp does not have this feature.
Secondly, 40wpc is plenty for an 89db rated speaker. I use a 12wpc SE amp on 88db speaker and the bass is tight and it can pound the walls down. I also use a 22wpc 6C33 based SET amp now and again, and if I had to turn that up my ears would bleed.
My speakers (Meadowlarks) happen to be well suited to tube amps, so much so that I get the best out of my amps. I am sure I get way higher distortion free SPL levels from my speaker than I could, had I been using speakers that are not tube friendly.
Your speakers are going to make or break your tube system, and the choice should not be made based on looking at rated sensitivity and nominal impedance only. I would suggest you talk to the manufacturers of your speakers and get their opinions regarding the use of tube equipment on their products. I doubt any manufacturer will advise you on an amp that will make their product sound bad.
40 watts into 89db is pushing your luck. Anything loud or dynamic may over-tax your amp and distort. Also, if you are new to tubes, 845's are not necessarily the best way to go. They are pricey and difficult to "roll" when compared to EL34's or KT-88's.
From what I know, lower impedance may run at slightly higher distortion levels. Many tube amps can handle 4 ohms or less but 8-16 ohm speakers are usually much more tube friendly.
Thanks Atmasphere and elevick for clear concise answers. I can finally grasp the issues. I will be dealing mostly with huge orchestral music and though I do not listen to loud vol, never more than 10 oclock on my JOR, still for a 845 tube the load may be too much for a 86 db speaker. The fact that its 8 ohms helps, but not much. With me speakers come first and so hope my 6550 tube will do the job. Next week will be the first time I will hook her up. Also i realized (was unaware of the ohm issue)the Tyler Lin Sig Sys is a 4 ohm speaker, so my dream of owning that model has changed now to Tyler's Lin Super Towers which is a 8 ohm and offers 4 W18's midbass per cabinet, which actually suits orch better as most cello, trombone notes fall in the range, not much in the below 35 hz. I see its important to research well before making any decision.
Bartockfan, FWIW, while you are doing your research factor in a couple of more issues, or at least possibilities....
1) Its not some much whether it's 4 or 8 ohms for a well made PP tube amp, its about the impedence curve and the minimum impedence. Some tube amps do quite well down into the 2ohm area and even come with 2 ohm taps. Its much more about the design of the actual tube amp than anything else generically speaking. Its also important to understand the actual output impedence curve of the amp and its synergy on the impedence (curve of the amp).
2) Be sure that the bass below 35 hz is unimportant to you by what you actually hear in your room, not just by looking at the supposed frequency response of instruments. If for example your room has a null in the 35 - 40 hz area your going to have nothing below 35hz to reinforce the bass which even starts to resemble the deep bass you would hear in a hall. Now if you room is flatish down to 35hz and you have a node at 30 hz the Towers may be more than enuf.
Perhaps its just because I don't listen to the Sig Systems at ear bleeding levels but I have no problems with tube amps with 40 to 80 watts in my medium sized room. In my room the Super Towers would not work due to room acoustics.
Newbee's first point on the impedance curve of the speaker is taking you to where you really need to be. I'll add in phase angle as well.
One other parameter I think that should be discussed is the crossover topology. How simple or complex the crossover is makes a tremendous impact into whether the loudspeaker presents an easy or difficult load. Tube amps like first order crossovers better than second order crossovers, and second order crossovers better than third order crossover, and on and on. On top of that, things like Zobel networks, trap circuits, and the like can turn things completely on their head. Take some famous loudspeakers, such as Thiels, with first order crossovers that so many compensation circuits - a total bear to drive.
The best generality I can offer is that you want the crossover as simple as can be. The opinions on single driver loudspeakers being a good match with a tube amp is true - because there is no crossover to suck up the power. Of course, you do give up frequency response.
Far too often, sensitivity and nominal impedance give such an incomplete picture that you simply need to walk away from what people will tell you, and give it a try. THAT is the only way you'll know...
Hi Pauly, here's what's up with four ohms: Yes, you can use the 4 ohm tap, but at a price. On most output transformers that have a 4 ohm tap, measuring the response of the amplifier on that tap as opposed to the other taps will reveal slightly lower power and quite a bit less bandwidth (both due to increased turns ratio and distributed capacitance in the windings). Sometimes there is also additional hysteresis loss. So tubes amps can make lower distortion on higher impedance taps as well.
So, all other things being equal, most tube amps will sound better on 8 or even 16 ohms as opposed to 4.
Well, I'm trying a brand new experiment today, and for the next couple of weeks. Trying a 30wpc Leben CS600 with my 89db/6 ohm (3.5 ohm minimum) VR4 Gen III HSE loudspeakers. Theoretically, this should not be a great match even though the Leben has a 4 ohm setting. Mid week a pair of 88.5 db/8ohm (5.5 ohm minimum) Castle Howard speakers arrive. Later in the week, a 55wpc Rogue Cronus arrives.
Yes, major system changes afoot...
Trelja, Good answer. Looking at the Thor's crssover designed by Appolito, one can see a simple yet effective design. The thing "just looks right". Its not loaded down with lots of components. Dr Appolito seems to know how to get the most music of the Seas Excel. And he did so successfully.
Newbee I realize that hypothetically it should not matter whether its a 4 OR 8 ohm laod for a "well designed tube amp". But realistically, most tube amps have their limits, depending on how well the trans are made AND the push pull tube on the block. Each tube sings differently and reacts differently to the ohm level. I refer specifically to 4 and 8 ohms, to keep things simply, disregarding 6 ohms.
Ideally tube amps work best on a 8 ohm load. Sure my JOR has driven one beast of a speaker and one moderately heavy load at 4 ohms, which was the Tyler Lin Sig Sys. But the JOR is not built for such loads over a long haul.
Pauly "4 ohms should not be any problem for a tube amp". But in my experience tube amps do not like 4 ohms, especially when the music gets complex, as in orch, even large jazz ensemble is rather thin sounding.
Push pull's , like SET amps can be picky on what speakers they prefer, for best potential.
I'll stay with 8 ohms.
The Tyler Lin Super Towers(8 ohm) is now on my radar and the Tyler Lin Sig Sys(4 ohm) is off.
Thanks Joe for that fine post, crossover network gets overlooked too often. I, like you, want to see whats inside the box BEFORE i buy.
A sealed speaker does me no good. Even if I don't know how the hell a crossover is made.
Hiend, well sure the 300 tube, even at 4 per mono block are not a tube for 4 ohm speakers. So If it takes a beefy amp like Roge, then you lose some finesse somewhere. IOW the delicate 300 monos has the finesse that the Rogue lacks.
btw why mention 96 db at 1 watt? I never fully understood the db thing. I have a general idea ofdecibels at a certain distance.
+++ Pauly "4 ohms should not be any problem for a tube amp". But in my experience tube amps do not like 4 ohms, especially when the music gets complex, as in orch, even large jazz ensemble is rather thin sounding. +++
All things equal I'd go for a higher impedance speaker, yes, but you are quite mistaken by making an across the board statement that tube amps do not like 4 ohm speakers. Decware has some speaker models rated at 4 ohms that are more suited to tube amps than 99% of all 8ohm rated speakers on the market today, and that no exaggeration.
+++ Push pull's , like SET amps can be picky on what speakers they prefer, for best potential.
I'll stay with 8 ohms. +++
A SET amp by definition is single ended and as such not push pull. I do agree that any tube amp, be they single ended or push pull are picky on what speaker they prefer. Where I disagree with you is that nominal impedance has little bearing whether a speaker is suited for use on tube amps. The actual impedance curve and crossover design are way bigger factors you need to consider.
Paul , nice post, and in agreement. FWIW, I demoed a KT88 40 watt intergrated (chinese model/low end lab) just to see how well the 88's work out on orch. The amp is the same weight as my JOR, but offer more tubes in the pre section. Very disapointing. The 86 db Thor's sucked the amp dry. So as you say, impedance of 86 db is something not suited for some tube amps. With a impedance that low, would you say that a important factor is how well the transformers are made/output power?
Tyler's Lin Sig Sys though rated 4 ohms, has a higher db rating at 92, so my little JOR was able to actually work the large speaker into good performance, if not excellent performance. I was very surprised as the LSS has 2 more drivers per cabinet to push vs my MTM design. I was surprised the JOR came through, due to the greater sensitivity of the LSS at 92. (in spite its 4 ohms).
Joe and Ralph,
I have Jm labs nominally rated at 8 ohms. They are 936 Electras, wich have dual 8 inch woofers the impedance will drop to 3.6 ohms. I am not sure which order X-over they have but I think they are 2nd order and probably have a fairly involved construction with a large induction coil etc. I also own speakers which are 16 ohms. I have 8 ohm speakers with rock solid 8 ohm impedance curves. None of these even comes close to the inefficiency of the Von Schweickert 2s in the WAF system driven by 40watt PP amp. (yes I know too many speakers and even more feel free to make offers) . Yet Joe as my witness the VR2s play to levels I wouldn't characterize as eye bleeding in a fairly large room 24X 12 X9 but loud enough that my wife always turns the music down whenever she comes into the room. It makes no sense because an average attack of flatulance will overcome the SPL.
I know you have both spent a good deal of effort, time and money on ensuring the bazzing speed that is the essence of what I like about OTLs.
Yet The new tube amps I have, are output transformer coupled and I credit the size of the trannies in them for making the JMs with a " difficult load" during low frequency passages, sound effortlessly extended and clean As loud as I want. I want a lot sometimes around 95- 100db.
Ralph brace youself- Joe has another 60 watt amp but it weighs about 70lbs mostly trannies. I have not found the trannie compromise you mention, the detail, extension are great. I don't care for bone crushing bass below the 28 cycles the JMs are supposed to make. My 16 ohm speakers are vintage JBLs since you like CAR that should have a good idea of that type sound. They are 1959s still as loud as you can take it not distorted using El84 based low powered integrated amps of that era.
My question is why do amps rated at as little as 9 watts per side but with massive trannies make the speaker sing in all but the worst cases, which are generally planars that drop to an impedance equal to a dead short.
Bartokfan I think you are confusing impedance with sensitivity. Nevertheless, both are factors that influence how well (or not well) your amp will do.
Rule of thumb is to have a speaker with simple cross over design (or better, no cross over), benign impedance curve, high(ish) impedance and high(is) sensitivity.
I will probably get flack from a couple of SET guys for saying this, but I do not believe any single tube is better per se than another at orchestra (or opera, jazz, rock or anything else.). However, not all amps are equal, and some will perform way over what their rated output would suggest they can.
Dont get bamboozled into buying a huge tube amp to drive tube unfriendly speakers. Get the right speakers and every tube amp will work well (or work as well as it can).
If somebody tells me his speakers worked fine with his 100 wpc plus tube amp but not with his 50wpc tube amp, I run away. That is the speaker I will never want own, even if I get paid to take them. Proper tube friendly speakers will work well with 2 to 3 wpc tube amps.
As far as orchestra/opera goes, I have had good results with all my tube amps on my speakers. These amps were 300B SET (x 2), 6C33 SET, 6550/KT88 SEP, EL34 PP (x 3), 6550 PP, EL84 PP. Im probably missing one or two, but the point is they all worked great for orchestra because I mated them with the right speakers.
Once you have tube friendly speakers, you can try any tube type and amp configuration and always end with a smile on your face.
I googled impedance. Its a load issue, 4 ohm speakers create a heavier impedance/resistance level vs a speaker at 8 ohms. Now I'm not sure why some Seas Excel designs are 8 ohms: Thor and several Tyler designs all with lower db levels at 87, and other Tyler designs with Seas Excel are at 4 ohms but have a higher sensitivity, 92. Both use the same copper magnet/motor. Truly a beast to drive correctly and will suck the life out of any tube amp that ain't got the Trans and/or tubes to push the current up and out the voice coils and make the speaker sing. i kind of envision the Seas Excel drivers as a panel/electrostat but in the shape of a conventional cone.
So impedance is the resisitance of the speaker to amp. Sensitivity is how well/or poor the speaker responds to 1 pure electrical watt.
Elevick, that is odd, the Lin Sig Sys is 4 ohm BUT 92 db. Tyler somehow figured out the crossover to function at a higher rate of sensitivity.
What happens in this case is that the vol needs to be turned slightly up to achieve same results on a 8 ohm speaker. IOW my MTM Thors at 10 o clock sound at the same db as the Lin Sig Sys at with the vol at 12 o clock. WITH THE DYNAMICS BEING EXACTLY THE SAME. Jadis has done something with the process in making the trans that allows the amp to drive as their web site says "any kind of speaker"...of course I wouldn't wish to push my luck on a expensive tube amp with 4 ohm speakers. This is why I say tubes "prefer 8 ohms", its a realiability issue. Never want to over work the horse, as they say.
My next speaker will be the Tyler 3 way called the Lin Sys 2, the speaker that Sally Renyolds reviewed in Absolute Sound last Oct. She had nothing but good things to say on its performance. The dual W18's in the Thor's worked fine for past 4 yrs, now I'm ready to move up the next level and get in on some the 25-35 hz's I've been missing.
On the topic of loudspeaker impedance and crossover complexity, "simpler" doesn't necessarily translate into "easier to drive". It is quite possible that elements in the circuit that add to the visual complexity are smoothing the impedance curve, reducing the phase angle, and making the speaker a much easier load to drive. Since we don't get to see the crossover and even if we did we probably couldn't reliably predict the impedance curve just by eyeballing it (at least I sure couldn't), the best bet is to look at the impedance curve itself. That is what the amplifier sees, and whether a tube-friendly impedance curve is arrived at by a complex crossover or by an extremely simple one doesn't matter to the amp.
How fortunate are we to have the participation of designers/builders like Duke who dispel misconceptions and provide facts that enable us to cut through the clutter?
It's the primary reason I keep coming back to Audiogon threads.
+++ I googled impedance. Its a load issue +++
If you googled it then it must be true? Okay
Have a look at Decware speakers theyre all designed to work with 2wpc plus tube amps. Most of them are rated 4 ohms nominal. http://www.decware.com/newsite/mainmenu.htm.
Ultimately it your money and your choice how to spend it. I personally dont have any issues with orchestral music on my system. And no, I do not have a hearing problem ;-)
Duke, sure there are exceptions (and I did state it as a rule of thumb), but the most tube friendly speakers are single driver non-crossover designs. If I may ask, what speakers do you build and are they designed to be used with vacuum tube amps?
Duke builds panels, which as you know require massive ss amp power.
Paul then you have a SET amp correct?
Would that be similiar to the 300 tube? Yes. I heard the 300 tube with orch, the load/complexity was overwhelming. Total shut down of the tube. A CJ mono block as well shut down on a ML panel with orch. So obviously orch overload is not limited to SET but can affect just about any tube amp, which in Push/pull config may have to do with the weakness in the trans. In SET's the weakness in "pulling off" orch may have to do with the characteristic of the 300/845/805 tube family
Boy, oh boy Bartokfan, you are the consummate source of bad information.
Duke builds dynamic loudspeakers that are tube friendly.
His Stormbringer and Jazz Modules are both 92 db/1w/1m, and have impedance loads between 8 ohms and 12 ohms. Very tube friendly loudspeakers.
As a dealer, Duke sells SoundLab speakers, among others.
And, what's up with stating Seas drivers utilize copper magnets? Copper is a non-magnetic material. The Seas Hexadym Magnets used in the Excel line and Millenium tweeter use neodymium magnets.
A little more research would be appreciated before posting.
Ok, here goes.
+++ Paul then you have a SET amp correct? +++
Currently I have only one SET, and that is a 6C33 based one.
+++ Would that be similiar to the 300 tube? +++
No, a tube has little to do with whether an amp is single ended or push pull. The 6C33 is very different to the 300B tube, although both are triodes.
+++ Yes. I heard the 300 tube with orch, the load/complexity was overwhelming. Total shut down of the tube. +++
Nothing to do with the tube. You made a bad choice with speakers. In other words, not the tube doing anything wrong, just you not knowing how to use the the tube amp.
+++A CJ mono block as well shut down on a ML panel with orch. So obviously orch overload is not limited to SET but can affect just about any tube amp, +++
Yes orch can overload any amp. In the same way I can drive any car into any tree, whether the car is a SUV, truck or coupe. No car made in the US today can drive through trees, so when you try to do that, the car will break. However, it is not the vehicles fault for driving into a tree, it is the driver that cannot operate the vehicle correctly.
If you drive the vehicle on the road, it will operate as designed.
+++ which in Push/pull config may have to do with the weakness in the trans. +++
+++ In SET's the weakness in "pulling off" orch may have to do with the characteristic of the 300/845/805 tube family +++
No. I have never ever heard this weakness you talk about. My 300B SET amps aced orchestra. I can induce any of my amps to fail in the manner you describe by seeking out speakers that will cause that.
I could also seek out trees to drive into when I drive, but as I rule I prefer not to.
Your last post was one of the most helpful & educational from a practical standpoint the I've read in a long while.
Bartokfan, it might take a long while(i.e. months, not a few minutes w/Google) to fully appreciate how well Pauly broke it down. Yes, it's true that there are many types of tubes, tube amps, etc. Each of them will react to cabling, speaker matching, room matching etc. You just can't conclude too much from a small bit of exposure at a show, in a dealer's showroom, etc.
My best advice for you is to seek out a local audio club, and spend much time listening to others' rigs in their homes. Slowly but surely, you will learn which element of various designs are to your liking(e.g. SET vs. OTL vs push/pull). Cheers,
Duke, apologies for that crass comment on what you actually do, which is build a fine speaker. Please excuse my lack of discretion. Paul its true I only have limited exposure to different tube amps, so will reconsider the SET's and other tubes on orch music. This is an issue with audiophilies, we can read about certain fantastic tube amps, but almost no opportunity to audition them.
>>which is build a fine speaker<<
He very well might but you've never heard them. Your opinion is irrelevant.
>>Paul its true I only have limited exposure to different tube amps<<
You have limited exposure to almost all audio components. Listening, not reading, is the key.
>>will reconsider the SET's and other tubes on orch music<<
It's not the tube or the amp; it's the speaker/amplifier combination whether you listen to Bach or Iron Maiden.
>>we can read about certain fantastic tube amps, but almost no opportunity to audition them.<<
Back to my second point. There are plenty of opportunities to audition. You have to get off of your a** and join an audio club, attend a show, or drive a couple hours. Don't say "we" when in fact it is "I" you are speaking about.
Audiofeil I ceratinly cannot argue any of those points ......and feel like I've won anything.
Do not allow my digressive comments and short sightedness keep us from gaining further understanding of this important subject. I am learning something here. Things maybe covered in other topics, but not sure where to look.
Perhaps the room size is a significant factor.
I recently took delivery of an integrated amplifer rated at 32 wpc that I am auditioning with 89db/1w/1m loudspeakers. The 30wpc is more than sufficient to drive the speakers to levels into the high 90db range without clipping. I suspect I could go higher.
Transformer quality is everything in a tube amp.
Hiend2: I use 45 watts a side from a CJ CAV50 to drive my 86 dB Vandy 2Ce Sigs in a moderately sized room and I have very little trouble hitting my comfort zone of 80 dB in my listening position about 10 ft from them.
I don't know where you get that opinion unless you listen to Metallica at concert levels (120 dB), then it all makes sense.
My JOR is,, well the one I sold...is rated 40 watts "conservatively" as they say...does "manage" to drive the 89 db speakers. However since i never biaed the unit, I am not sure there was more highs it could have achieved. On jazz, pop, R7B there was authority. In big complex orch I was always looking for more authority. So the 40 watts was never enough to make the orch "bloom". This is the only reason I sold the amp and looked for more power. I was say a "normal" 40 watt tube amp is not going to deliver the goods on a 89 db speaker. I always felt there was more in the orch that was not comming through.
You NEVER biased the tubes in your JOR? Thanks for admitting this. It completely invalidates every post you have ever made about your comparisons of different tubes, including your preference for the KT90.
When you receive your new tube amp, unless it's an autobias model, you MUST bias your tubes for the amplifier to sound as it's supposed to sound.
Inexperienced members of Audiogon who are looking for guidance read posts and take them as gospel, not realizing the egregious errors sometimes made during the testing and listening process.
Readers of your posts deserve better.
The guy who bought my JOR , who actually owned 2 previous JOR's said the amp "should/ought" to be biased every year. Take that up with him. I figured he knows what he is talking about. said tubes wear every yr and a slight bias adjustment 'could be made". Obviously take all my posts as though i am a learning newbee. I hope no one takes anything i say with too much seriousness. Just ideas to open discussion. We can all learn something here. You too.
It's too bad you received bad advice. Tubes should be checked every few weeks or so for bias, and every time you install different tubes, they have to be biased.
Good lesson learned.
We can all learn something here. You too.Yup. I learn something here every day.
Tvad, all the time I had the JOR i never thought to bias the unit to see if I could get a tad more highs. Now that i have the Defy 7, if there is something I don;'t like about the sound, i'll look into biasing the unit. But since the amp has few hours on it, should I bias the amp? It should be biased correctly with few hours use. I've never heard tube amps need biasing regularly. I should look into how to bias the defy 7. Not even sure how to go about it. There is a wooden board at the bottom. Will have mt tech friend assist me first time.
Also I learned the JOR had a pre out and never took advantage of in use with a sub. I will have Tyler replace the woofer in his Taylo with a Seas Excel W26. And so will keep my Thor's, which I had for sale 3 days last week.
The things we learn, one must research and think for oneself of all the options avaliable.
If the Defy is not autobiasing, then it requires biasing the first time you install it and power it up. Then, the bias should be checked at least monthly thereafter. Why? Because tubes age, and the bias shifts. Autobiasing amps take care of this for you.
Your amp's manual will explain the biasing procedure.
I just checked the biasing on my TAD-60 as I just changed an output tube and had to make adjustments to get the balance right as it did not sound right after I changed the tubes. Turned out I had to readjust two out of three tubes. Then I checked the sound and it sounded nice and balanced again... So, I agree with TVAD that you have to check the bias either every six months as Paul Gryzbek recommends or when the music doesn't sound balanced... On the TAD-60, Paul supplies you with a $10 meter and gives you instructions on biasing the unit. On the 07s, the biasing meter is on the unit...
Tvad, ROTFLMAO. Don't hang around any crosses. You are far too nice.
Bartockfan, may I suggest that before you burden the forum readers further with your 'experience' using tubes that you take some time to read about tube technology and get some understanding of whats actually going on. You might just learn what the benefits of properly biasing tubes are and what the risks of not properly biasing your tubes are. Its got nothing to do with getting "a tad more highs" as you seem to think.
Hmm, I was just about to buy my first tube amp but am unsure now, after reading this thread. I'd be grateful for any comments on whether the following would work together.
My speakers are B&W 804S's - 3 way vented box design. They are rated as having a 90db sensitivity and a 'normal' impedance of 8 ohms. But, the minimum is impedance is quoted as being 3.0 ohms. I know that some say they need a powerful amp to work at their best, but they have been fine with my 35wpc Class A Sugden A21SE.
The amp I was thinking of purchasing (to get a taster of tube amps) is a Yaqin MC-100B. This is a chinese brand and employs 4 x KT88 tubes. It is rated at 65wpc in ultralinear mode, or 45wpc (into 8ohms) in its standard mode. I'm not clear what ultralinear is all about, but do you think this combo would work?
Divad, You might consider posting a new thread - I think a lot of folks not already signed into this one will open it and see it, and some of the more knowlegable folks that have posted probably may not be following it any longerby now.
I think it is possible (actually quite probable) that a tube amp with a wattage limitation of 65 in Ultralinear can drive a 90db speaker depending on the actual impedence curve of both the amp and the speakers and how they interact. Your nominal impedence and minimum impedence are not ideal for just any old tube amp, unfortunately.
Usually ultralinear is going to be a bit more forward/focused and triode will be a little more recessed and relaxed. Usually, but this is very amp dependant, and either mode can better fit with certain speakers that the other. I have a 'triode amp' which sounds neither laidback nor unfocused, and responds much as another amp I have when its in ultraliner.
Your speakers are fairly well know (to others) but you prospective amp is not. I would suggest that you post here and on Audioasylum and try to find folks who have actually used a tube amp with your B&W so you can find out what they need to drive them.
If you can find out, it is helpful to know exactly where your speakers minimum impedence droop appears (at some frequencies it won't be near as important as others) and if you can find out the maximum output impedence of the amp and at what frequency it appears. With that info there are some very knowlegable folks about who can give you some advise.
I hope this helps a bit, I know it really doesn't do much to specifically answer your question. But, if you are a gambler, you can afford a buy and sell loss should you be unhappy, and you are not a bass nut (thats usually where you will run into problems) you can always get a tube amp and drive it off its 4ohm tap and hope for the best. :-)
65 wpc might be enough to drive the B&W804S in the frequency where the 3 ohm load is located.
I recently drove my VR4 Gen III HSE loudspeakers with a 55 wpc Rogue Cronus tubed integrated amp. The combo was surprisingly very good. Lots of bass and heft. The VR4 Gen III HSE are 89db/1w/1m, 6 ohm nominal load, with a dip to 3 ohms.
Divad i had a chinese KT88 amp very close in specs to the one you are looking at. I can only speak for my speakers, the amp did not have enough power. Manufacturers can say "amp has X amount of watts". but are they quality watts?
My Jadis Orch Refer rated at 40 watts, blew out the water a Rotel ss amp rated at 100 watts. Go figure. The quality of trans and specs of the tube is everything. In my experience the KT88 tube is better for higher sensitivity speakers.
I only like KT90 and 6550's,. Well I'll hear the 6550 first time in 2 weeks.
btw not a fan of B&W..too british
This experience based upon the author having never biased any of the tubes.
Properly biasing tubes in a non-biasing tube amp means everything to the proper sound of the amplifier. Without having ever biased the tubes, one cannot legitimately comment on the highs, lows...or any other aspect of a tube's sound.
Sorry to beat this into the ground, but as long as you continue to share your experience listening to tubes in a tube amp which was never biased, then I will continue to caution new readers to take your comments with the appropriate perspective.
Frankly, I very much look forward to the first post you author after you have biased your amplifier. I suspect you will experience such a revelation in good sound that you will be physically shuddering with giddy enthusiasm.
True i did swap the KT90's for th eKT88's w/o biasing. But also had a KT88 NEW intergrated for demo purposes. The amp did not perform on 88 db speakers. Divad may have better luck with his KT88. Both are chinese. Though cayin is chinese I consider that line on european standards. Ming da, and Melody are alos of european standards. The one Didad is refering to is not.