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In the Forum: Audio Discussions
In the Thread: Devid Berning amplifiers: the anti-trnsformers frenzy?
Post Subject: Circuit.Posted by Merlin on: 9/25/2007
 drdna wrote:
 Romy the Cat wrote:
David got rid of transformer and replaced it with a DC transformer, claiming that it is “better”.
And I should point out that not only is there still a transformer in the circuit, but many other components are added, including transistors.  I have no doubt that this topology give reduced measured hysteresis distortion, but I wonder what all the other components are doing to the sound?


Here's what Berning said about the circuit when questioned

"The ZOTL falls into a generic class of amplifier described by the acronym OTL both technically and in spirit. The power conversion transformers called out by the patent cannot and do not operate at audio frequencies. The semiconductor devices called out by the patent drive these transformers at a fixed 250 kHz and do not operate at audio frequencies or as amplifiers. The patented ZOTL circuit is a two-way coupling circuit that performs impedance matching like an audio output transformer, but does not have any of the limitations and distortions imposed by audio output transformers. This circuit is in no way a buffer, such as a transistor output stage in a hybrid tube-transistor amplifier. There is no power gain, and more importantly, the speaker “sees” the tube transfer characteristics and the tubes “see” the speaker’s dynamic characteristics."

Next something I have said in the past about the circuit when it was suggested it was a switching amp

"Power is transferred from the valve to the speakers as the plate current in the valve varies in response to the audio signal on it's grid. As the anode current increases, the current drawn from the converter bridge power supply increases in proportion to the converter transformer ratio. Since the speaker is connected in series to the primary winding , it's current increases by the same amount.

The switching transistors in the impedance converter bridge are not variables in the signal path. The current through the loudspeaker load follows the transfer characteristics of the valve. With a Mosfet switching amplifier, the signal is converted to PWM . With the Berning this is not the case . So again from my point of view, to use the term switching amp is misleading - switching amps are Class D. This is not class D"

And to help matters further , something the late Terry Cain had to say on the subject

"The Bernings use a device, (not mosfets or transistor nor another gain stage)to change impedance up into mhz, and to an output suitable for driving spkrs. The -device- is a unique Berning designed inductor of sorts, has a "wound" turns ratio, this is where the confusion lies. The tube directly drives the load, through this high freq "inductor".

Inductor is a misnomer because no "inductor" has ever been made this way.

Personally I think it is every bit -otl- as circlotron only much more advanced. OK, it uses less than 1% of _some_ inductance so it is still using inductance but in a weird and unusual way. So in a way it -has- an inductor. But not at all suspect to the usual saturation and inductance distortions like every other tube amp, except circlotron and hybrid otl's.

Berning is unique, and far away the most advanced circuit for tubes period. True to thermionic dissapation as a musical fuel for amplification, it does things no other amp can. It's very stable, efficient and very low in distorion and hum. DC couled and flat response to 2hz and ultimate stability."

And finally the flowery prose of Doctor Gizmo,

" MARK MY WORDS: I have seen the future and it is ultra high frequency switching power supplies with regulators for tube amplifier who aspire to the thermionic concresence of coolosity. David started this trend almost two decades ago and now others will soon follow. Remember my 100% batting average.

Because so few have experienced David’s new ZOTL, and even fewer the single-ended version, it is easy to understand the angst in the Rec. Audio chat groups. There is much whining and complaining about this circuit because it is so threatening to makers of conventional transformer coupled amplifiers and conventional OTL amplifiers, but let me assure you that like The Harmonic Plasma Transducer, David single-ended 300B ZOTL is, in the truest sense a breakthrough in the most serious end of the audio arts. This circuit is not an incremental step, but a major leap forward in thermionics, is totally unexpected, understood by few, including me, is totally "untweakable", and the best reason in the world why others would want to assassinate David. Who would have imagined listening to a directly heated triode without an audio transformer? Who would have imagined a single-ended directly heated output transformerless amplifier....and the elimination of OTL’s impedance sensitivity?

Let me be clear that neither of these products are designed for "sodbuster" audiophiles. This is ultra serious stuff for those who have been witness to the thermionic fire; to whose who have walked across the burning coals, and are living on the edge. This is the place you arrive at after you have taken Sid Arthur’s journey, and know the sound of one 300B clapping. If you have any doubt about David’s alien genius just consider this...in a ten pound box David is able to create what it took the savants of New York Audio Labs to accomplish in a 250 pound form of the Futterman OTL-1. After listening to ZOTL when you pick up the box, which weighs less than you preamp, your brain goes.....Duh! How is this extreme level of anti-gravity performance possible my fellow earthlings?"

I post these to shed some background and to answer some technical questions - not to make any claims as Paul seems to think. In a subjective hobby there is no one true path.

Paul, you have an attitude - please let it rest. To correct some errors in your rather agressive post though, no I did not make any claims other than stating that my SET was not bandwidth limited as Romy had suggested all SET's were. And secondly, no you didn't guess I was talking about the Berning - Be did. Given your ignorance of the subject at the beginning of the thread I now find it most amusing that you claim to have heard the device on numerous occasions and preferred the Lamm. Forgive my cynicism - you appear to feel threatened by the unknown here. There's no need to be - none of us know everything.




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