What is the best OTL out there?


Hello. I've always been curious about OTL amplifiers, but never tried one except for the very unusual (and wonderful) Berning Siegfried, which was both SET and OTL. I wonder if there is an agreement as to which OTL currently in production can be considered to be the best. Ciao.
ggavetti
Try Atma-Sphere. I would be surprised if you were disappointed.
I've listened to a few different ones and have to say the Atmasphere Novaron's have been my favorite. Now with that being said you must, with any OTL, use a speaker that has a flat impedance and the higher the better.

(Dealer disclaimer)
I wonder if there is an agreement as to which OTL currently in production can be considered to be the best. Ciao.
Ggavetti

06-03-15

LOL! There is generally no agreement on anything in the world of audio. Tubes or solid state? Digital or analog? Horns or dynamic speakers? Best cables? Best amp? Best speakers? Sorry, you will get answers, but no agreements.

The old joke is if you ask 10 different audiophiles a question, you will get 11 different responses.
how many OTL manufacturers are there currently in production?
Yup, so 2 of the 11 are Atma-Sphere and Tenor. That leaves room for 9 other votes. Cheers,

Spencer
The Joule Electra Right of Passage is a pretty special amp (probably the Destiny as well, but I have not heard it). That leaves room for 8 more
If your wattage needs are modest, less than 20wpc, the new Music Reference OTL is absolutely amazing. Heard it a week ago on loan from Vaughn Loudpeakers. Get the one upgraded witb Eichman posts. Must be heard to be believed....
The Atma are no-brainer choices. They have the design very refined.
Agree with Jmcgrogan2, really when you think about it what is the BEST of anything? The limits of the experience of the responders will correlate to some of the responses you'll get but what will that tell you? Then there is the system itself, and the room, and the power feeding the system. The Tenor was "proclamated" at one time as the best of the best by guys who were willing to pay the most and declare what is best. What is most important is that the electrical characteristics of the amp/speaker interface is maximized, the higher and more stable the impedance characteristics of the speaker the more suitable. Graff, Fourier, Counterpoint (SA 4), Atma-sphere, Trancendent, Berning, Joule Electra, Tenor, NYAL, and Futterman are all OTL's I've heard in different systems over the years including my own.

Not all of the above were known for their reliability but I won't name names. Each are capable of good to great sound in the proper system and room.
Check out David Berning. Big splash at the recent Newport show.
david berning big splash at axponia and newport. Great stuff.
I've heard Berning and Tenor in show environments and have been impressed.

I'm using a full Atma-Sphere rig with Silver Edition MA-1 monoblocks and appreciate the accolades bestowed upon the brand! This gear is extraordinarily agile and will reward you with a spectrum of sound due to its ability to realize the characteristics of any 6SN7 in the circuit.

I'd like to try the Novacrons, but need more power for the MegaLine III.
Macrojack are you referring to Berning's recently introduced 60 watt 845 SET ZOTL amp?
Tubegroover-
Yes. No personal experience. But my history with Rick Brown makes me comfortable about conveying his endorsement.
This is the ONE I've been waiting for from Berning, a Class A single ended amplifier with zero feedback, no iron and 60 watts of power! Sure would love some feedback from those that have heard this system. Unfortunately the price puts it out of the realm of all but the well heeled. I wonder how long it takes David to complete a pair of these amplifiers?
Best sound is subjective, but if you want the best support, the best service, the best upgrade path, the best reputation and history, then purchase Atma-Sphere.
I have owned Joule (VZN-80), Atma (M-60), and Berning (ZH-270), but not all at the same time. Tried running the Berning source direct and it did not make it for me. Had the Joule and Atma at the same time and both are excellent. In the system I had at the time, for my taste, I preferred the Atma. Given the current status of Joule as a company, I'd agree w Brf.
Atma-Sphere would probably be my first choice. Ralph is constantly posting on forums trying his best to help people. The vast majority of them don't even own any of his products. For me personally, stuff like that is a huge plus.
ZD542 - Have to agree with your endorsement of Ralph Karsten. He's one of the most sincere and gracious people I've ever met in this industry.
Einstein is another good one.
I haven't heard Roger Modjeski's OTL's, but his transformer-coupled amps sure are good. Plus with the way he runs his tubes so conservatively, his OTL amps are likely to need less maintenance than other OTL's, which can be pretty expensive to keep tubed.
Mactone OTL monos.
Thanks for all your inputs! I see a clear convergence on Atma-sphere, and I will definitely look into it. A friend of mine has their MP1 preamp and raves about it. I suspect that something like the combination MP1 and their M60 amplifier might be very interesting. I have a pair of stacked quads to drive, and I don't need more than 50WPC.

I personally think Berning is a genius based on what I listened to (as I said I had a Siegfried and also some of his earlier non-OTL amps), but I wonder if he is overpriced relative to the competition.

A friend of mine (a famous musician and serious audiophile) swears his favorite amp ever is a Tenor. Never had a chance to look into it. On the negative side, he also said it had some reliability issue.
Atma-sphere is certainly good, if is it the best, I don't know. In my case, OTL amps bettered heavy-duty solid state amplification. I had a flagship chain - Krell FPB600 driving Dynaudio Consequence speakers. I bought Atma-Sphere MA-1 and got them factory upgraded to mk 3.2, and to my ears, this sounds better. But it happened only when I changed from 8 ohm speakers, to 12 ohm (Audiokinesis). You get the diamond edge of OTL amps only through high-ohm speakers. If not, it may sound ok, but it is not optimal.
At the Newport show a few days ago I had a chance to hear OTL monoblocks from both Einstein and D Berning. OTL's are definitely closest in sound to no amp. Both were pure and endlessly open on top and both had tremendous presence and authority. Both were 70- 80 watts as I recall. In my judgement the system with the Berning amps sounded somewhat clinical and less than natural on top when pushed. The wide open bandwidth of an OTL can also invite unwanted super sonic spurious crap that gets into the picture... if not properly addressed.
The Einstein OTL mono's were my preference...(that day). Big, insanely open, realistic, clear and alive... and totally non-fatiguing. For the record, the one non-OTL amp that sounds closest to no amp is the Technical Brain amps from Japan just beginning new dist. in the U.S.

Cheers
"The wide open bandwidth of an OTL can also invite unwanted super sonic spurious crap that gets into the picture... if not properly addressed."

It's ultimately an issue I hear as well. The level of transparency offered by an OTL mandates that EVERYTHING be balanced less hearing a bit more than you bargained for, that balance between clinical and musical which might be heard as an initial WOW as the brain starts working to fill in the blanks vs. being relaxed and engaged in the music, not the sound. When they are right, dialed in with the right components and addressing room issues, they can be quite special in their presentation.
Oh, don't you know it, Tubegroover!
Tubegroover,
Nice observation/comments. I agree with your perspective.
Charles,
I had to laugh, but "super-sonic spurious crap" is a dead-on description of what might be a deal breaker for some people. But the wide-open bandwidth spoken of is literally like the door thrown open wide on your speakers. Quite a realization.
Best OTL I've heard is Graaf GM200. Too bad Graaf is building SS amps now.

Dealer offered me a great deal on his demo but just graduated from college so didn't have much disposable income to buy it.
Another vote for Atma-sphere; not only for the product but for all the support after the sale as well.
Sufficed to say, if you have never sat in front of a properly set up kit with OTL amplification, you do not know what you are missing... The level of transparency and sense of open sound stage is simply exhilarating and astonishing and may well leave you with a possible conundrum. It is likened to an audio enlightenment. Once the clouds have parted, the brilliance shined through, and the singing have sung, you can't go back to pretending music anymore.

Count my vote with Atma-Sphere. I have had the MA-1 Silver Edition Mk.3s for some years now and couldn't be happier with their performance.

When people start this "best" business stuff though and are speaking of one component in an entire kit, within a listening room, and to someone's particular ear, it leaves me sort of itchy-scratchy. Perhaps a better comment I might make from my listening experience would be to say that, paired to the right speaker the Atma's are without musical compromise. 
Most OTL  are not producing enough plate dissipation for a pair of tubes,Imagine for a pair of 6c33c tube with max.of 60 watts plate dissipation can produce more than 25 watts class A of power, 3 x of 300b output in SE.
Not trying to change the subject, it just seemed like all the posters here would be the ones to ask. I would like to get recommendations as to whether anyone uses an OTL amp with Quad 57's. I bought a pair of these to try, after all these years, I have never heard a pair so I figured it was time to try them out. I have read on some other forums that a lot of the recommended amps mentioned here were if I remember correctly also recommended for the Quads. Does anyone have any experience with this pairing? 
Most OTL  are not producing enough plate dissipation for a pair of tubes,Imagine for a pair of 6c33c tube with max.of 60 watts plate dissipation can produce more than 25 watts class A of power, 3 x of 300b output in SE.
Its not a matter of plate dissipation, its a matter of output impedance. For some reason people really do want a low power OTL, but what happens is as you decrease the number of power tubes more and more of the total power generated by the output section is absorbed by the output section itself. So if you build a bigger amp its more efficient and the individual power tubes run cooler.

Not trying to change the subject, it just seemed like all the posters here would be the ones to ask. I would like to get recommendations as to whether anyone uses an OTL amp with Quad 57's. I bought a pair of these to try, after all these years, I have never heard a pair so I figured it was time to try them out. I have read on some other forums that a lot of the recommended amps mentioned here were if I remember correctly also recommended for the Quads. Does anyone have any experience with this pairing?

Quads and OTLs have a history together going clear back to the 1950s. We have a lot of customers that use our amps with ESL57s and ESL63s which are good speakers for OTLs due to a fairly benign impedance curve.
Hello atmasphere, I recently bought a JBL Paragon. I have not received it yet, but it's on its way on a truck. My current setup is a CJ ART 2 preamp, and an EDGE NL-12 amp. I wonder if an OTL might be a better way to go...any experience with Paragons?
I hope it arrives in good shape!

Our Michigan dealer has Paragons (if I recall right, the big one and the little one). He says our amps work fine with them. I've not experienced it myself- but you could ask him- he's the guy that makes the Classic Audio Loudspeakers.
Thanks for the info Ralph, BTW, your amps look amazing! I see we have a dealer here in NJ. I will have to make  the trek for an audition. Thanks again!

Mike
I have a Quad ESL 57 & Quad II & Quad 22,but the ESL are ineffecient speaker at 86db,A lot of fullrange speaker will be far better.
I run a set of Atma-Sphere M-60s with my 57s. I ran them alone for a while then added a set of Zero autoformers in between them. Use the 2x or 3x settings. Nice improvment.

There's some out there who designed and build their own  OTL that uses better tubes like KT88/120/150,,300b,,VV52b,,even 211 / VT 4C can  be used and  they are more efficient than the ones  on the market today.
I have had the ZOTL 40 for about 3 days and it is killer. I heard it at the Newport show and went ahead and pulled the trigger finally. This is David Bernings most recent design but is built by a small company called Linear Tube Audio. Mark Schneider has assembled a fine team of engineers and is capable of producing these a bit faster than David by himself has been able to in the past. Another plus is the very reasonable price for this new line.

i am enjoying the best my room has ever sounded and it's much better than what I heard at Newport not that it sounded bad. My Janszen zA2.1's have never sounded so good and more than enough power. If you are familiar with David Bernings amps, I also own his ZH230 which was the best sounding amp ive ever heard until I got this ZOTL 40.

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I hope someone worked on the Futterman circuit to cure it’s well-known problems. Harvey Rosenberg and George Kaye tried for years without being entirely successful. Both Ralph Karsten (Atma-Sphere) and Roger Modjeski (Music Reference) have designed and offer better OTL amps than any Futterman.
There's some out there who designed and build their own  OTL that uses better tubes like KT88/120/150,,300b,,VV52b,,even 211 / VT 4C can  be used and  they are more efficient than the ones  on the market today.
This statement is false- there are no OTLs based on any of the tubes listed above.
How can you be sure,I build and designed these types of OTL and they sound excellent.using KT120,KT88,VVT52b,300bMaybe you are just concentrated on your OTL.
I build and designed these types of OTL and they sound excellent.using KT120,KT88,VVT52b,300b Maybe you are just concentrated on your OTL.
Can you indicate the impedance of the speakers you use with these OTLs? These tubes were designed to work into impedances that are vastly higher than the 4 to 16 ohm impedances of most modern speakers.

For example, without an output transformer it seems impossible that a 300B, which in most and perhaps all versions can handle a plate current of at most about 0.1 amperes, could supply anything close to a reasonable amount of current (and hence a reasonable amount of power) into an 8 ohm speaker. Even if several such tubes were used in parallel.

On the other hand, if you were using something like the horn-type antique radio speakers that were made in the early 1920s, many of which had impedances of 1000 or 2000 ohms or thereabouts, I can see that such a design might work.

Regards,
-- Al


Al,
Intelligent and logical inquiry as usual. Xonex77 could you share more detail about your very unique OTL amplifiers using these unusual (for this application )tubes. This is quite interesting. David Berning makes a 300b SET /OTL amplifier  (Siegfried) to my understanding.
Charles,
Thank you, Charles.  While the Siegfried and certain other Berning amps are described by Mr. Berning as OTLs, and are considered by many to be such, and by all accounts I have seen those are brilliant designs and excellent performers, in between their output tube(s) and the output of the amp they employ a transformer operating at RF frequencies, and also a number of solid state switching devices.  Therefore, despite their description and despite the fact that they are considered to be OTLs by many, they are not truly OTLs for at least two reasons:

1)While the output transformer is not an AF (audio frequency) transformer, as it is in most tube amps, an RF (radio frequency) transformer is still a transformer.  So the design is not Output TransformerLess.

2)The use of solid state switching devices in the output circuit, which are "after" the output tube(s) in the signal path, arguably makes the use of the term OTL meaningless, since aside from a few McIntosh designs nearly all amps having solid state output stages do not have output transformers either.

I know from past discussions that Ralph/Atmasphere would strongly agree with what I have said.

The patent on Mr. Berning's "Output Transformerless Amplifier Impedance Matching Apparatus" can be found here (although it addresses a push-pull version rather than the SET version).   In the first figure note all of the "stuff" between the output tube and the "load" (i.e., the speaker), including a transformer and numerous solid state devices.  And note in the introductory text:
A linear audio amplifier includes a push-pull pair of vacuum tubes operating in a linear amplification mode coupled through a pair of dc-dc switching power converters to an external load impedance.  Each power converter includes a transformer with one or more secondary windings that drive rectifier circuits, and the resultant dc voltage sources are loaded by their respective tubes....  The effective turns ratio between primary and secondary windings of these converter transformers determine the voltage/current step-up/step-down relationships between the tubes and the external load impedance. 
The last sentence is identically applicable to any conventionally designed tube amp that has an output transformer.  (Although in both cases it is the voltage that is stepped down and the current that is stepped up, rather than the opposite which is what the wording of the sentence might seem to suggest).

Best regards,
-- Al
   
Hi Al,
Thanks very much for your illuminating comments.  Well it sure seems that the Berning is an OTL amplif only in the sense that it lacks the "traditional "output transformer. Given information you provided calling it an OTL design is a generous stretch. I can see why Ralph would express reservations. 
Charles, 

charles1dad:

It's time to buy that "son of Siegfried Amp" sold here on Audiogon :)

David Pritchard