David Berning "Holy Grail" 45 SE ZOTL now exists

Yes folks, it's here. For those of you who have been following my system, there has been some anticipation of the delivery of this new amp. And it has arrived.

For those who aren't aware of this amp. It is a fully custom one-of-a-kind handmade amp by David Berning that was constructed to my specifications by special order. It carries a "Prototype" designation, as a non-production unit.

I have named it the "Holy Grail" because it has characteristics that have never before been available in any amp at any price. It is a Single-Ended Triode design using Type 45 output triodes, and 6SN7 drivers. The amp is a variation of OTL(output transformerless) called ZOTL that is proprietary to David Berning, and is the only circuit in the world that can commercially achieve true SET configuration without an output transformer. This is special enough, but this unit also features choke-loaded plates for much greater linearity than resistive loaded plates, and has a custom choke hand wound by David Berning. To top it all off, it is powered by battery only, from a 12vdc deep cycle marine battery, that provides the cleanest power possible, with no AC grunge, and no step-down transformer or rectifiers in the power supply, for a smooth ripple-free power feed, and no hum fields generated by the power transformer. This is the only amp ever made with this particular set of features, and makes it probably the most advanced form of tube amplifier ever made.

Prior to the invention of ZOTL it was impractical, or impossible, to make a true SET amplifier that was OTL. Now it is possible, and is being done, not only in my amp, but in the Berning Siegfried as well. Achieving this SET "magic" sound without the intrusion of an output transformer between the triode and the speaker is truly revolutionary, and revelatory in its sound quality.

Choke loading is being used by some of the best tube amp makers to improve the sound of their amps, and is a very nice improvement over resistive loading, but comes at a high cost. I selected this because of the sonics, and not the cost factor, because I wanted the best in a cost-no-object design.

Battery power is the cutting edge of power conditioning. It totally eclipses what power conditioning can do, and goes into territory that exceeds any AC powered amp.

The entire audio circuit is hand wired point-to-point. Top quality parts,jacks, and posts are used.

I selected the Emission Labs mesh-plate 45 triodes for their sound quality, and ruggedness over all others for this application, and use NOS Sylvania 6SN7 GT tubes for the drivers, for their "sweet" tone quality, and delicacy of detail.

The reason I selected the name "Holy Grail" for this amp, was because it has achieved something that has been sought after for years, but has never been attainable until now. The magic of SET, in an OTL configuration with the ultimate in power supply, and a choke loading, and type 45 tubes, which are legendary for their awesome tone.

I have done some preliminary listening tests with this amp, and the sound definitely lives up to the name. It is indescribe-able really. My basic impression is that it sounds like a high-end solid state amp, with triodes. By that, I mean that it has full frequency range, with no roll-offs on either end, and has punch and slam like a solid state amp, while having the SET magic sound all the way from top to bottom. I know this sounds unbelievable, but that is what it is. This amp has test charts accompanying it, and it reproduces a 20kHz square wave with a perfectly vertical rise time. Try that with an output transformer. 30Hz square waves look just as good. The amp is not DC coupled, so the coupling cap introduces just a touch of trail-off on the square wave peaks. Very minimal. On the load-line scope traces, there is no looping distortion. The bandwidth extends into the RF zone, which has a "hole" aroung the 250kHz ZOTL carrier, and then picks up again and extends to over 500kHz. Is that wide enough bandwidth for you?

I could go on and on about this, but this is simply the most awesome amplifier ever made, in my humble opinion. And the sound is just exquisitely beautiful. If you could imagine a SET with SS highs, lows, dynamics, and slam, and no grunge or grain at all, this is what we have here. I am almost at a loss for words.

I just wanted to share this with whomever wants to hear about this, because it is truly a landmark that has never ever been done before. The Holy Grail.

I will try to answer any questions or happily entertain any comments anyone may have about the amp, or my criteria for its design.
Very interesting concept. What about power output? How long does the battery last, and what are you doing to re-charge it?
Oh gees TWL, I'll have to jump in here an say that my David Berning Direct Drives might be the Holy Grail, we'll have to do a Holy Grail shoot out :)
How about this, you can keep the Holy Grail designation, and I'll say mine is the Arc of the Covenant, cause it can really kill you if you take the top off :) but all in all, fitting in the biblical sense that his name is David :)
What pre-amp/linestage do you use? What is your source? Speakers? Interconnects, speaker cables and digital cable? Near field listening or do you listen in a large room?
Thanks for all the input, guys! I'll try to answer some questions.

First, I will post some pictures on my virtual system page, when I get the photos taken. Since this amp was a prototype, it has a perf-metal chassis, and I am responsible for making my own "pretty" enclosure. I am going to do that next week sometime. Then I'll do the pix.

Power output is rated at 2 watts per channel into 8 ohms. It is made for high efficiency speakers. I use Lowther Voigt Pipes. They work real well, and I get very high SPL levels, probably in the area of over 103db. When I turn it up, it gets too loud for my ears to take, before I hear any distortion problems, so it is plenty loud enough for me.

The draw on the battery is 5 amps continuous, when it is on. This gives many hours from a deep-cycle marine battery. I use an automotive style battery charger to charge the battery, when I'm not playing the amp.

The cost so far, without enclosure, is about $2k per watt.

Okay Allan, you have a custom Berning too, but I got the Holy Grail name first! I'd love to hear that amp of yours, also. Another example of a unique Berning design.

I use analog only source, from a Teres 245/OL Silver/Shelter 501. Mitch Cotter step-up transformer, MFA Magus(highly modified), and Lowther Voigt Pipes(made by me, and modified from original design) using EX3 driver units. All cables are DIY.

The room is 14'x24' with a 16' vaulted ceiling, and I listen in the far-field. My chair is about 12 feet from the speakers. SPL is too loud to hear someone talking real loud, right next to you. Fills this room well, and I can feel the bass "slam" in my chest from 12 feet away. This is not a "weak sister".

Having lots of fun!
Hi Twl,
Thanks for sharing. Looks like a winner! I've been looking for this post since yesterday. When your system is powered up with no music playing can you hear any noise (static, hiss,or hum) from your Ex3's?

I've been following the evolution of your system closely. What had initially intrigued me about what you were doing was the elimination of crossovers. Since Lowther introduced a refined design of their drivers and eliminated, to a large degree, the infamous "Lowther shout" and is further improved with the use of the Voight enclosure design it's even more interesting. That these speakers can be driven by just a whisper of amplification makes battery power practical for anyone.

Being a solid state guy that really loves the glorious mids of a tube system and turned off by the lack of bass response these same systems provide, you have really got my interest in this simple design path. It doesn't take a rocket scientist to add up the total cost of your system and it's a modest investment by audiophile standards. My guess is that your system rivals those costing 5X more or better. Are we getting a glimpse into the future? I think so.

My hope is that David Berning licenses this technology to other manufacturers since it's such a long wait to take delivery of his products.

Thanks Tom. You've taken a leap of faith that few others have the balls to do.

Congratulations, Tom. I know you've been looking forward to getting this beauty for some time. Glad it's living up to your expectations. So, are you out as far as CDs are concerned? I guess no CD player can compete with your beloved Teres/OL Silver/Shelter combo, huh? Have you been able to replace most of your vinyl collection?

Enjoy the music, and happy holidays.

Chris, I have to say that CD is out of the picture for me at this time, and the foreseeable future. At least in my home system. I'll still use them in the car. I am not happy that this is the case, it is just reality. I have spent alot of money and effort to try to get the best sound possible. The difference between CD and analog, on a system that is as revealing as this one is, is about as wide as the Pacific Ocean. When I have tried some very good CD players, and SACD players on my system, it quite literally sounded like there was something broken, or wrong with the system. Can't help it, that's the facts. I would love to be able to just plug in a CD and get the same sound, but it ain't going to happen, at least with what they have now. I doubt that it will ever happen, really. So, I am not going to try to fool myself into thinking that the sound is the same, it is painfully obvious the minute I turn it on. That's just the way it is. Instead of beating a dead horse, I use the CD's in the car, and the LP's at home.

The vinyl collection is up to about 1500 now, and growing. I have a long way to go before I get near what I once had. But I have most of the "key" albums I really wanted, and am working on "filling it out" now.

Lak, I am pleased to say that I can only hear a very very slight amount of hiss when I put my ear directly in front of the speaker, when no music is on.

The amp has very good input sensitiviy, about 300mv for max output. This means that the preamp does not need to be turned up very high to achieve full volume. That translates into lower hiss factor. Also, the Cotter gives alot of gain to the Shelter, and requires very little gain in the phono section, which also reduces hiss from this critical area. From most audiophiles perspective, this system is about dead quiet in the noise floor, even with 100db efficiency speakers. Easily as good as any solid state system, and probably better than the majority of SS systems. Noise is simply not a concern at all. The noise rating of this amp is better than -110db, which is at least as good as just about any amp there is, and way quieter than most any tube amp.
Patrick Lugnut, I would be careful for what you hope for, it might be a long wait for a Berning product now but from what I know of Berning designs, the complexity and the time to assemble a unit, the price will go out of this world for anything he now makes.

So TWL's baby would cost you over $10K, I'll rather wait :), I am sure however, it would be in a pretty chassis.
Now this be what we're talking about, Holy Grail indeed. What more could a purist tube afficionado want, Me? I need a few more watts but damn Twl if you and Berning haven't taken this technology to another place with your prototype. Congragulations!

I might be a little envious as mine is push pull and works off grungy AC (actually my AC is pretty good) I gotta say I would love to hear your zotl, single ended, battery powered 2 watt amp driving those horns. This is indeed what audio is all about and I'm sure Gizmo's spirit is somewhere out there clapping away.
Congrats on our new amp. I have a 811 Siegried with Avantgarde horns and am entranced by the music played thru this system. I would love to see a formal review and comparison with other SET amps (if you can borrow one). Enjoy.
Tubegroover, I would like to feel as though I am helping to carry on Dr. Gizmo's legacy with this design, and I have even mentioned that to David Berning. As you know he and Gizmo did some things together, and Harvey even coined the name "ZOTL".

After reading most of the articles on the Triode Guild, I felt that a battery powered, single ended, choke loaded ZOTL, with 45s, would be Harvey's idea of the "creamiest of the Triode Cream" and a virtual cornucopia of "Thermionic Coolosity". To say nothing of the studly appearance of those 7" tall 45s standing above deck. And again, it is David Berning (and me), who reached up to new heights of Alien Triode technology to make this bold step into the far reaches of cosmic triode universe.

I think the Dr. would be proud that this step has been taken, and maybe might have even been taken by him, if he were still alive. But since he's not, I took the step to advance the state of the triode art, and get all the attention from Miss Triode Guild 2002.

Dr. Gizmo lives!
Asa, I'll be looking next spring for preamps. Jayarr, thanks, and I know you are loving your Siegfried!
TWL....so happy you have your new baby! From what I've read this should keep you in Hi-Fi heaven for quite some time. Keep us all posted as to the progress...

BTW...I am not a horn person....and you indicatred that you get gerat "slam" base from your speakers....do you use a regular driver for the bass?
Rwd, my speakers are not horns. They are direct-radiator single-drivers, which use a complex loading of the rear wave, called a Tapered Quarter Wave Pipe. The moniker used is generally "Voigt Pipe" named after the inventer. The rear wave of the driver is funnelled through a cabinet that uses Transmission Line, Bass Reflex, and rear horn loading, to augment just the lower bass frequencies. This is not perfect, but does a pretty good job, and does not impart the colorations like a front-horn system does. This is not to say it has no colorations, but they are less severe than the front horn types, and are more like direct-radiator speakers with some vented-box type colorations. Not bad, but nothing is perfect. I get the efficiency I need with no horns.

The "Slam" I get is from the Lowthers, believe it or not. They only go to about 40Hz, but have a rolloff below that, and the dynamics of the driver is imparted to the bass frequencies as well as the rest of the range. When you hook up an amp with the bottom end speed that the Berning has, you actually do get "slam". This was not previously the case because most times, Lowthers get used with typical SET amps, which have some challenges in reproducing fast tight bass. It is not like a pair of super-subs with dedicated Krell amps, but it has a modicum of "slam" in the sound. More than you would ever expect from a 2 watt SET amp. It sounds more like a SS amp in the bottom, like maybe a Pass Aleph 30 watt. Because it has the extension, speed and lack of bloat that normally is not present in most SET amps, and is usually characteristic of SS amps. But the excellent tube tone quality is still there, just fast and tight. Midrange and high end are also lightning fast. This system is a speed demon. Not a hint of sluggishness here.

Thanks for your sentiments, about being happy for me getting the amp. I appreciate that alot, and I am happy with it.