Thanks, Thorty40, very cool pix. |
Jtinn, my recommendation to you as a dealer would be to audition the Berning line in your system. I believe that if you do this, you will pick up that line as your new reference standard. I am sure the Tenors are exquisite amplifiers that anyone would be proud to own,with great sound and beautiful build quality. I do not intend to knock them and perhaps went overboard with my "flat as a pancake" statement. However, as Tubegroover stated, Berning has established a new path for OTL that creates a new standard in the OTL field. The typical circlotron OTL circuit topology has been superceded. The inherent circlotron weaknesses have been replaced with a superior design. And, of course, the previous cathode follower and Futterman designs had been surpassed years before by Ralph Karsten and his Atma-sphere circlotron design. I love OTLs and all of the great amps out there that use OTL design. I just have to recognize that there is now a superior design that will take us further toward OTL perfection, and that design is the Berning Zero-Hysteresis OTL amplifier. Cheers. |
Thorty 40, I couldn't pull up your URL with my search engine. Would love to see that design. If you could find another way for us to see it, it would be much appreciated. |
Regarding Berning, my dream amp is the Seigfried: a 300b ZH type OTL w/12wpc and dual volume pots to allow direct input. It's killer. And like the ZH270, it will drive low impedances with authority. Talk about perfection, a 300b, pure class A single ended triode, ZH type OTL,with low heat/low power consumption, 20 year tube life, direct input capable, and drives difficult loads and is extremely reliable. And I believe, auto bias adjusting. I think it's around $7500. I'll bet it will squash the Tenor amps flatter than a pancake. Looks really cool, too. BTW, I have the Berning MicroZ OTL(1wpc,pure class A triode) and it is a jewel. I have NOS tubes(Mullard 6201,Sylvania 6sn7wgt) in it and there is no way I could describe the performance level(that you would believe, anyway). You have to audition one of these, with good single driver high-eff. speakers. It will knock your socks off, and you will never think the same way again about low power amps. All the accolades spoken above about the ZH270 also apply to the MicroZOTL. If you choose your speakers to match it, you will never need more amplifier.(Maybe a separate sub/amp if you like that set up). Also, it makes a great bi-amp system with one on each side for inexpensive OTL bi-amping if you like 2 way speakers, or even a crystal clear tweeter amp for multi-amp systems. It even has a headphone output jack. No one that has listened to mine believed it is only a $750 amp. Very highly recommended.(It will also run on a 12vdc battery which completely eliminates power grunge problems and the entire 120vac power supply section, or you can just plug it into the wall if you want, no wall-wart, uses IEC connector so you can use the super duper power cords, too. |
C'mon, where are the Graaf and Croft people? And how about the Transcendance folks? |
Cool post, Tubegroover. All modern OTLs take the music one step closer to the truth. One comment I would make about the load stability is that the large number of tubes is also an attempt to lower the output impedance of the amp, not just current drive. The output impedance of the Berning amps is 2ohms or less, depending on model. And this is the case with relatively few tubes. This is the real breakthrough in the design in that the RF carrier system replaces the output transformer's task with a much higher turns ratio than possible with iron. Thus allowing fewer tubes, better efficiency, less heat, and a lower output impedance than previous OTL designs. And, it's not really in the signal path, just carrying it. Grid drive. Not cathode follower or circlotron. All new. With previous OTLs, damping factor was a problem because the amps output impedance was high enough to sometimes be above the load impedance and damping was seriously compromised.With a 2ohm output impedance the Berning design breaks new ground with respect to damping and does so with few tubes. In fact, in my MicroZ OTL, the output tubes are 6sn7's. Normally a preamp tube, and a great one. Tube heads out there know that preamp tubes are generally much more linear than power tubes. This is really the first time a linear tube such as the 6sn7 is actually driving a speaker directly. It is amazing. And very short signal path, too. Detail is dramatic. Midrange is liquid, and bass is fast and solid. The sound is balanced from top to bottom. If you just take the sound, not the power level, it is the equal or better of anything there is. I can't believe that I could afford such a thing, but here it sits - all 4 pounds of it! Must be a dream. David Berning is a genius to have thought up this level of tube "groovosity."(As Harvey aka Dr Gizmo, called it) |
Srouse, I haven't heard the Exemplar amp. Did you hear a 2A3 or a 300B? Checked into it at the Bottlehead site. It seems that he(John) has gotten some input from the Bottlehead people on his amps. Bet they sound great.90kHz bandwidth, must be a helluva output transformer! |
Jtinn, BTW, Kris is entitled to his opinion, just as you are. Just as I am. Please do not feel threatened if another amp line surpasses your favorite. It happens to your customers all the time, when you have something new and great to sell them. Probably doesn't bother you a bit that they are going to take a bath on the money they lose selling their old gear and paying you profit on the flavor of the month. After all, how else would audio businesses continue to make money. I've worked in several audio emporiums and know people that worked in others, been to CES, and other shows and rubbed elbows. I know the comments that are made between dealers and mfrs. It's all about churning. Just like the stock brokers: buy, sell, buy, sell. How many "turns" will you get on a particular product in a year, is the major concern. And how much margin. Hype the latest hot item, and next month hype the next. If a customer's system gets superceded by a better(newer) product, well "that's just the electronics biz." But if you've got $350k tied up in the minimum stocking order to retain a dealership, then you better believe that amp is going to be the "best you ever heard".I hate to be this hard on you, but you threw down the gauntlet and now I'm telling you that your opinion cannot be considered objective because you have financial interest in certain products selling well. Conflict of interest, I believe, is the term. You should recuse yourself from this discussion due to conflict of interest. |
Just for the record Tubegroover, I haven't worked in audio for almost 10 years now. I feel bad about hammering Jtinn like I did, but when you are an audiophile and you hear stuff like I heard at trade shows, it really scorches your hide. They want to herd us around like livestock to the slaughter with their hype and magazine reviews. Now, I know there are alot of great products out there and I am not going to say that 1 product is best for everyone, and am sure that you or Jtinn would feel similarly. I am just very sensitive about the revolving door of product hype based on the need to sell. Sorry If I offended anyone(Jtinn). I have no knowledge of him personally doing any of the negative things I mentioned above. |
Jtinn, thank you for your comments. As I mentioned in my last post I apologized for any offense that may have been taken, and said that I am not accusing you directly of doing the bad stuff that is common in the industry, as I have no basis for such. Just for the record, I am not the person that made the comments comparing the amps in different systems.That was Kris, not me. I just made a conjecture on what I thought would be the result of the comparison. From what others have said here on the forum, you are a good guy and have been helpful to others, so I defer my pointed remarks. However, the industry in general is most deserving of those pointed remarks, and I think that it has injured the hobby with its much less-than-pure approach towards its customers. I am now sorry that I included you in that group, in light of what I have now learned. Enjoy those Tenors and perhaps, one day, I'll even have the chance to try some in my system. Happy listening! |
Mes, your point was misconstrued by Tubegroover, not me. I understood your point perfectly and thanks for your comments on my post and on the thread. |
Mejames, I would think that any good speaker to your liking would work well with the zh270. Bear in mind that it is 70 watts per channel, so the selection should include that criteria. As you may know already, I am quite opinionated in my speaker recommendations. For HT however, I am less stringent in my opinions. Generally, I would say pick a speaker that would fit your liking for both categories and use them for your mains/fronts for both audio and HT. Since I don't know your particular taste or budget, it's hard for me to recommend a particular speaker, but a full range dynamic type would fit the bill for both applications. An 8ohm load sounds better than 4 on the Berning OTLs. So I would go with 8ohm. Probably an efficiency level of about 92-95 db would give plenty of room for the dynamics of HT. |
My reading of the schematic on the Berning patent shows no "output transformer." There is a coupling transformer for the RF carrier network that which is what actually performs the impedance matching function. Since this coupling transormer does not perform the function of "output transformer", with the attendant sonic weaknesses(ie phase shift, saturation, and HF rolloff), it cannot correctly be termed as one. So, if you want to nit-pick, here's a nit-pick in return. I will allow that the Berning could not be termed "total transformerless" but OTL does apply for the above stated reasons. The Zero Hysteresis moniker could not be applied if this amp had an output transformer. If you look at the square-wave response on an oscilloscope(as shown in Berning's "white paper") you can easily see the difference. No ouput transformer could behave like this. Perhaps you have been talking to Jennifer Crock, as she has been referred to in an article as saying the Berning is not OTL. I will not speculate on her reasons for saying this, but her misunderstanding of the circuit is not Berning's concern. He makes amps. So, yes it is OTL, no it is not TTL, it is radically creative and brilliant, and it sounds great. No knock on any other great OTLs out there, just my meager expanation on a minor technicality that I wanted to address about the OTL designation. |
Without trying to be argumentative, I agree that if one wants to call the amp non-OTL because of the "coupling transformer", this gives one an ostensibly good reason. On the other hand if one wants to call it an OTL, one can use my reasoning in the above post. I've already posted my reasons. I think that the main point is that it addresses the inherent difficulties in circlotronic OTL circuits, without resorting to a "conventional"(is that alright?) output transformer for impedance matching. Does so with considerably fewer tubes, with lower heat, lower energy consumption, and excellent reliability. I mean absolutely no disrespect to the Tenor people, Atma-Sphere people, Graaf, or anyone else. So now there is a design that provides(apparently arguably) the benefits of both OTL and traditional output transformer amps with neither of their typical weaknesses(although not perfect). I say that this can only be considered a historic event, much like the circlotron before it. Regardless of how one categorizes it, as several mentioned above, it exists and cannot be ignored. How it will fare in the marketplace is up to the performance level that users feel it posesses, at the various price points. Just like any other product. |
I like all OTL's and many other amps as well. It just seems to me that as soon as something was said about Berning vs. other OTL's, the fur really flew. Very interesting. Seems to be a very sensitive issue. I hope everyone is enjoying their amps, and I think it is very informative that readers hear the different sides of this issue. I doubt that anyone on either side will be swayed by this discussion, but the process gives opportunity for each to re-think, re-evaluate, and better understand their positions. And good heated discussion is great to "hone" your argument. I am enjoying this thread immensely! |
