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.
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However I took atmospheres comments to apply to solid state as well but I could be wrong about that as I don't have much knowledge about solid-state here.My comments include solid state and class D as well. All amplifiers have lower distortion into higher impedances and this always translates to smoother sound with greater detail. Given that some solid state amps are really expensive, the only explanation I have for the persistence of low impedance speakers is that speaker designers are often not that aware of how the speaker/amplifier interface affects the sound and the performance of the amplifier, and by that I mean **any** amplifier. Of course, when you put an OTL on higher impedance speakers, that's when the magic happens and on such speakers I've yet to hear any competing technology sound better. But of course I make OTLs- I could be biased just like the power tubes in an amplifier are. |
@realdeal, OTL owners always say that the brand they own is best even though they haven't heard any other brands (not quoting you verbatim here since your choice of wording was so vague/unfortunate). I would say that your observation is largely correct, just as it would be for the SET crowd, the push/pull pentode contingency, the solid state class A fanboys, etc., etc. Bottom line, this approach is endemic to virtually all audio discussions concerning any audio gear genre you wish to become involved with. Get used to it. |
Yes I have heard some very good solid state as well. However I took atmospheres comments to apply to solid state as well but I could be wrong about that as I don't have much knowledge about solid-state here. I run a pair of atmosphere M60s and I am a big fan though admittedly have not heard any other OTL. I did have some pretty good single ended triode amps and preferred the 0TL to that. |
Hi analoluvr admittedly with all things considered I do generally prefer tube amplification rather than solid state. In all candor however I have heard very good sounding solid-state products so I won't throw them all out with the bathwater 😊. Good implementation of tubes sounds more natural to me more often than not. Just a personal observation over the years. I do acknowledge that solid-state dominates the audio market. Charles |
@ michaela: I have used original Julius Futterman OTL's successfully with Quad 57's and KLH Nines. I presently have a Harvard Music stereo and a pair of H3AA's. The 6HB5 and 6LF6 TV sweep tubes Julius used as outputs could handle 1.5 amps of current apiece. Making them suitable for this application. However, speaker impedances below 6 ohms still stress these OTL's too much. An autoformer is then recommended. |
Atmasphere's point that "all" amplifier types make less distortion when driving higher impedance speaker loads is an audio pearl that is unrecognized and under appreciated by many listeners. I understand this dilemma given the dominance of 4 ohm speakers in the current High End audio marketplace. Transistor power amplifiers made these lower impedance speakers quite viable. Charles |
I love that Bernings amps get picked apart yet when someone says that they use an autoformer after the output of a OTL the only thing heard is the crickets.I don't think anyone picks apart the Berning- its an excellent amplifier, a brilliant design, with excellent reviews and isn't an OTL. As a separate issue, using an autoformer on an OTL allows you to solve problems- usually one where the speaker desired is simply unsuitable for the amp otherwise. We have a lot of customers here in the Twin Cities that like to use Magnaplanars with our amps, and especially with our smaller amps, the autoformers are a good idea. A good number of people that don't have OTLs also use the autoformers, including people with solid state amps, for no other reason than it sounds better. This is true because all amps have lower distortion when driving higher impedances. Whether an amplifier is an OTL or not is an entirely different subject from how it sounds. Personally while we make OTLs, I don't see other OTL manufacturers as the competition so much as just other amplifier manufacturers in general. |
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, |
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 |
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 |
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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. |
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. |
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? |
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. |
"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. |
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 |
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. |
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. |
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. |
