what is an ideal tube amp

I have recently purchased a new pair of ClassicAudioLoudspeakers T-3,I believe there efficiency is about 105db/w-m .for my bedroom system.The impedance of the speaker is 16 ohms (varies between 10-20 ohms) I am presently powering them with a Gryphon Antileon Signature biased at 50 watts for class A.The sound is wonderful imaging is perfect in all three dimensions with fantastic clarity and non fatiguing,but very sensitive to sweet spot.I am told by that horn speakers sound best with tube amps,particularly set amps.
I have not had a tube power amp for over 25 years and that was a poor experience.Where I live there are not to much choice of audio dealers who support tube equipment.That means that I may have to purchase an amplifier without the ability to audition it in my system.I need help ,most tube amps I have seen looked at do not have a 16 ohms speakers tap,does that matter??I particular a 10watt amp with only output at 8 ohms I would lose half the power which may not be adequate?I would like to avoid mortgaging the house for cost of the amp,in other words those very unique Japanese amps with a price of $5,000 per watt are out.I do prefer balanced inputs as my Meridian 861V6 has XLR outputs,I use the Sooloos system extensively,however I can also use my Einstein preamp could with all my sources,Zanden transport,DAC or for sacd the Accuphase 800/801 combo.
I would also prefer a trouble free tube amp which does not require constant tuning or tweaking.I listen primarily to classical music.Your counsel will be greatly appreciated.
I power Cain & Cain Abbys (95db) to fairly loud (not concert) volumes in my medium (17 x 35 w/vaulted ceilings) room with an upgraded Sophia Electric Baby amp (10w).
sounds like an ideal setup for Atmasphere amps which I've heard w/Classic Audio speakrs & it was fantastic
Call John at Classic Audio and ask him what he uses for his own system.
I did talk to John,he is currently using an Allinic amp in the shows.However I am still curious whether a Wavac EC-300B will be better or a Krozila( I do know the spelling)or some other ,and how important is the 16 ohms output.
SET or OTL should work very well. Personally, I would probably go with a 45 SET or an OTL. The small Atma-sphere amp (S-30) would deliver 45W into a 16-ohm load and delivers the liquid sound of tubes while having a very solid bass foundation. The 45 will only deliver about 2W but for your efficiency level and bedroom size room would handle just about any music you throw at it. The 45 has more musical presence than just about any other tube I've tried. Honestly, I can't think of any tube or tube topology that would not work in your system.
Sounds ideal for an OTL. I too heard them with Atma-sphere; impressive indeed.
If you want to save some bucks check out Mapletree Audio preamps and a pair of their Super Stealth amps. Classic circuits and just different enough. SET's will work with horns but having a more controlled bass lower output impedance will never hurt.
04-05-12: Ramy
I did talk to John,he is currently using an Allnic amp in the shows. However I am still curious whether a Wavac EC-300B will be better or a Krozila( I do know the spelling)or some other ,and how important is the 16 ohms output.

I knew the answer but thought it better to hear from the designer of the speakers.

One of the guys in my group has Classic Audio Speakers and he's using all Allnic. The Allnic has no issue with the 16 Ohms, I've heard the combo for countless hours of great music.
You sell Allnic right Albert?
Did John offer any opinion on the Atma-sphere or Wavac with regard tho his speakers?

Why don't you ask John his opinion about Allnic performance versus other brands. I don't need to be speaking for him.

You might even ask him what he thought about my set up, he visited here and listened with me.

Audiofeil, You sell Allnic right Albert?

Yes, and exactly why I would not speak for the other person on this subject even though I knew his opinion.

Sibelius statement is accurate:
Honestly, I can't think of any tube or tube topology that would not work in your system.
Sibelius (System | Threads | Answers | This Thread)

There are easily two dozen tube amps that would work, Classic Audio speakers are quite efficient.
I heard John's speakers at last years capitolfest. He at first had the atmosphere amps running, which sounded very fast and detailed.
Once John put the allnic in the sound tonally fleshed out without losing the detail. It sounded more natural to my friends and I.
We really enjoyed our time in John's room. I thought it was one of the best sounding rooms at the show, IMHO
Your speakers offer great flexibility with amplifiers as others have said. I`ve heard this speker with OTL amps and it will work out fine.I`d however pay serious attention to the suggestion of the Allnic 300b. This amp(or another high quality 300b amplifier)when mated with a top level 300b tube(Takatsuki,Sophia Royal Princess, EML) will sound simply fabulous,full tone and provide stunning realism.
Best of Luck,
"what is an ideal tube amp"?

Based on the info in your post, maybe a pair of Cary 805AE monoblocks.

1. You get 25/30 watts of pure SET Class A power and 50/70 in Class A2 for those Classical Music peaks.

2. They have 4,8 and 16 ohm taps so you stay at that power instead of losing half.

3. They have been absolutely trouble free/fit and forget amps for me.

I alternate between them and my Pass XA.5's to drive my Magnepans. I can only imagine what they would sound like on your 97 db CAR's.
Rogue would be another option i would consider.

Probably hard to go bad with vac or arc also.

Ramy, gotta say i really like your collection of gear! Building around gp
and car speakers. Probably doesn't get much better than that!
John also has an Atma-Sphere setup, with a fairly well-optioned MP-1. He has had Atma-Sphere amps since 1989 if memory serves.

I bought a set of T-3s in 1998. There has been no looking back. They have been updated with the dual woofers, new crossover and the beryllium field coil drivers. My room is 17' x 21'. The efficiency of the speaker is more like 98 db, not 105 (that is more typical of his Hartsfield reproduction). Any amp we make works very effectively on the speaker- keep in mind that such amps are what the speaker was designed with.

The S-30 does very well on the T-3!. I tend to play the system louder than most audiophiles as my front end is relatively impervious to room-borne vibration. What this means is that it is very relaxed even when driven well above 100 db, so I can occasionally clip the S-30. Not so with the M-60 and MA-1 :)
Get an Atma-Sphere S-30 and don't look back.
The sound is wonderful imaging is perfect in all three dimensions with fantastic clarity and non fatiguing
Based upon this statement and your comments/experiences with tube amps, I suggest you stay with what you already have. You can spend a significant sum of money, get different but not better sound, or screw the sound up with an amp that requires more user care than you want to commit. Plus the amp will go in your bedroom where the tube glow and space heater aspects may not be welcome.

Completely ignoring the above, you might also consider a Pathos TT. It has balanced inputs and only uses 2 12ax7s tubes to drive solid state output devices. It should work well into the 16 ohm load.
Albert, I don't care what John's answer is since I'm not going to buy the speakers and I'm perfectly happy with my Atma-Sphere M60s. I was asking Ramy if he had asked the question since he spoke with John and is seeking comparisons (the question was begged). I'm sure all the amps being mentioned are excellent; however I only heard these particular speakers with Atma-sphere and they sounded fantastic.

I responded, thinking you were creator of the thread. I now realize that was Ramy. Sorry for the confusion.
I only want to make one point. The 16 Ohm load is not a detriment when employing tube amps. The higher the load the happier the tube amp is. Tube amps do not lose power into higher resistance speakers they actually perform better. This is the opposite of what happens with solid state, I am surprised no one has addressed this point.
My answer to the question is a repeat of what some others have said. Any tube amp will work well. Given the overall quality of your gear I would choose either the Cary 805 as above, or a single ended 845 amp, a Vac 300B based amp or one of Ricardo Krons amps as the OP had asked about. You are in a great position, go for it.
Atma-sphere should go back to the older style amps. I like the way the older units look compared to the newer ones. The ones with the handles are what I am talking about. Very cool looking.
Regarding the statements that have been made about losing half the power vs. not losing any power, if the nominally 16 ohm speaker is connected to an 8 ohm tap, in most cases the truth lies somewhere in between. It depends on the output impedance of the particular amp, and in some cases perhaps also on the current capability of the particular amp.

The output impedance of the 8 ohm tap of most (but not all) tube amplifiers will be considerably less than 8 ohms, corresponding to a damping factor considerably greater than 1. As a consequence of that, and assuming that power delivery into 8 ohms is not limited by current capability, the amp will not be able to deliver as much power into 16 ohms as into 8 ohms, but the reduction will be smaller than in the case of a solid state amp having near zero output impedance. The reduction will be MUCH smaller if the amplifier has a particularly low damping factor/high output impedance, such as SET amps commonly have.

An actual increase in power delivery into a 16 ohm load connected to an 8 ohm tap, compared to an 8 ohm load connected to the same tap, would occur in the relatively uncommon situation where the amplifier has a damping factor significantly less than 1, corresponding to an output impedance significantly greater than 8 ohms, and/or if its 8 ohm power capability is limited by current capability.

A separate question relevant to connecting a 16 ohm load to an 8 ohm tap (assuming the amp is not an OTL and has output taps) would be whether or not a perceivable increase in distortion might occur in some cases. Perhaps Ralph will speak to that, as I don't know the answer.

-- Al
If a tube amp with an output transformer has a 16 ohm tap, it will have slightly more power and certainly less distortion when driving 16 ohms. This is because the output transformer is more efficient. In fact it will also exhibit more bandwidth- often with greater bass extension.

With transistors you lose power, but you also lose distortion- causing the transistor amp to sound smoother and more musical. This is because there is a non-linear capacitive aspect to almost any semiconductor junction, which is magnified by current. This aspect contributes to odd-ordered harmonic distortion, which is unpleasant to the human ear. By reducing the current (i.e. going to a higher impedance load) odd-ordered harmonics are reduced. This is evident in the distortion curves of all solid state amplifiers, even class D.

With OTLs, depending on the size of the amp, you may gain some power- in particular with smaller OTLs. For example the S-30 makes 45 watts into 16 ohms. With larger OTLs this may not be true- for example with our MA-1 the output power is unchanged. What is more important is what happens to distortion and efficiency of the OTL! In all cases it will operate with less distortion, meaning that it will sound smoother and more detailed. The increased efficiency also means that you will get less heat with less power drawn from the wall, as more of the power generated by the amp will be dissipated in the load rather than the output section.

IMO there is every argument for 16 ohms **if your goal is sound quality**. There is no argument for 4 ohms regardless of the amp, unless your goal is **increased sound pressure where sound quality is less important**, *and* you have a solid state amplifier. IOW 16 ohms is a simple way of making the speaker seem more transparent, smoother and more musical, as opposed to 4 or 8 ohms.
The new style stands a chance of fitting into an equipment rack.
If you prefer set and forget, if you don't want futzing, you might be wise to pursue a self-biasing tube amp. Personally I would consider the little Berning.
If you want to keep the budget small, there'a a guy on Audio Circle selling an Almorro 205. Or you can buy my Audio Mirror 20 watters.

And, of course,the Ongaku option appears occasionally.
I`m not an engineer but everything you wrote about higher impedance speaker loads has been observed by me with personal experiences(all positive).I really don`t understand the proliferation/dominance of 4 ohm load speakers with modest efficiency ratings. What advantage does this pathway offer to explain it`s popularity? It just seems to force one to buy bigger and more complex amplifiers to drive them.
Ramy, I have an S-30 Mk II that I haven't gotten around to listing due to the difficulties with this site recently. Add gmail to my username here and e-mail me if interested. A fabulous amp but no does not work well with my new speakers. If you like it Ralph can update it to the most recent version.
What is the tradeoff? I assume there is one; or it is simpler to design 4ohm speakers?
Charles1dad, take a look at this article, it will help in understanding my explanation that follows:


Four ohms came in with the transistor- we all know that. However, along with the transistor came the new Voltage design rule. The rule has been in place since the mid 1970s. IMO the rule has its problems and one of them is this: with it has come the idea that if you parallel two speakers, the efficiency increases.

Now, if that were really the case, it would violate some pretty fundamental rules of physics- and clearly falls into the same area as perpetual motion machines. That is to say, you don't get that increased energy for nothing. What is really happening is that there is confusion between the idea of Efficiency (how much power it takes to drive a speaker) and Senstivity (which is sort of the Voltage rule equivalent, IOW how much voltage a speaker has applied to it for a certain amount of output).

Now into an 8 ohm load the two are the same. For example if you have 1 watt into 8 ohms the voltage is 2.83 volts. But if you apply 2.83 volts to a *4* ohm load you will have 2 watts in the load. People tend to use the two words interchangeably and that is where the confusion lies. Power (1 watt/1 meter) is the older Power Paradigm spec and Voltage (2.83V/1 meter) is the Voltage Paradigm spec.

Now tubes have always been kind of expensive to make power. So to deal with that, in the old days high efficiency speakers tended to be more common, as was 16 ohms. When transistors came in, one thing that was not lost on the industry was the fact that you could build a transistor amp that made the same power as a tube amp, charge about 90% of the tube amp price, but have about 10-50% of the cost of building the tube amp. IOW follow the dollars.

Now this was not lost on the speaker manufacturers. When it was seen that you could double the power of some transistor amps simply by cutting the impedance in half, some speaker manufacturers began making 4 ohm speakers to get that extra output from the amp. You see, building high efficiency speakers is expensive because you have to have precision voice coil gaps to get the efficiency. By going to reduced precision by increasing the voice coil gap, the cost of the speaker went down. But if you went to 4 ohms you got 3 db of Sensitivity "back". Again, for such speakers the industry found that they could charge slightly less than the high efficiency models, but the cost again was dramatically reduced- they made more money.

I think it would be great if this was simply my opinion (one would like to think that the changes we see in audio have to do with increased fidelity rather than just making more bucks) but you don't have to look very far to see that this is what went on. I can name plenty of examples beyond these two and I am sure others can too.

So- if we turn our backs on the money-making schemes and focus instead on how to make the equipment sound better, right away higher impedance in the speakers emerges as a simple solution.
One of the great posts!
Thanks for your explanation. If it does cost more to build high efficiency speakers that would explain(to some degree anyway) why 4 ohm speakers dominant the high end audio segment.
I would not put those amps in a rack. They get pretty hot and I always enjoy looking at them when I visit my friend.
Thank you all for the inputs and advise.Specially Atmasphere.I did further discuss the choices with John of ClassicAudio and has settled for a an initial experience with an older version of the Atmasphere S-30.Learn what it takes to live with a tube amp,experiment with it and upgrade it down the road should it be beneficial.As to the efficiency of the T-3 the version I have have the electromagnets for some of the speakers resulting in an efficiency of 100db/w-m,with nominal impedance of 16 ohms and a range across the frequency band of 10-20 ohms.I have learned a great deal from your responses.
Try a Sophia Electric Baby Amplifier which is of first class sound and is very affordable (and liquid in the used market )in your system first. So you know what you would expect for a good tube amplifier. Then you know if you should spend money for single ended 300B or anything else?
Thanks for all you responses.I took the plunge and purchased Atma sphere S-30 which I upgraded to the latest.I also purchased the Atma sphere M-60 monos .Both are fantastic the sound is incredible and like Ralph explained the bass response was far superior to a solid state amp.