Why no threads on OTL amps?

jtinn,

Apparently I ruffled a feather or two when I stated my "opinion" that I preferred the Berning to the Tenor. I do agree that the systems were different. I cannot imagine, however, that manufacturers mate equipment at these shows with speakers and associated equipment that they did not feel brought out the better attributes of their products. That being said, I like most people in this hobby, am not afforded the opportunity to take home any and every product for evaluation on a master reference system. This being the case, I choose to participate in attending shows and frequenting audio shops so I can hear as many products as I can and gather as many "opinions" on equipment as possible. I do this with a clear concious in an effort to make an educated and yes, subjective decision on what products I like and dislike. Because as we all know in this hobby, it all comes down to what you like and nobody else.

Kris

Thorty40: This was made clear back when they were introduced. While it is a brilliant design, it is not an OTL. It is a transformer based amplifier that is biased by a high speed oscillator to reduce hysteresis effect of the transformer.

An output transformerless amplifier does not have a transformer between the tubes and the speakers. The David Berning amplifier has one after the tubes. Ask to see the schematics published in the patent application. In your own statement, you aver:

"Ok, the RF re-mapping occurs through the use of a tiny RF transformer at a carrier freq. of 250kHz."

The transformer you speaker of, is in between the tubes and the speaker leads. Hence, it is in no way an OTL.

To reiterate, it is a brilliant design and while having the ability to drive impedance challenged speakers, if put head to head with a proper OTL on a stable load, you might be surprised at which one sounds better. Again, I want to make it clear that if I had a limited budget and a tough load to drive, I would give the Berning amps real consideration.

Hi Jonathan

You are right, by the truest definition of OTL, the Berning is not. The patent application and schematic is on Berning's website for those interested. It may be a moot point, the proof is in the listening. I am not certain how it would compare head to head with an ideal load next to the top tier OTL's with all other things being equal. I will say that next to the Transcendent 25 watt amp, there really is no contest. My wife, who could care less, noticed it immediately before she even knew I changed anything. The Berning doesn't take a back seat in any performance area. Then again it is more powerful and this can certainly come into play in the equation. The big difference is the clarity at all frequencies of the Berning over the Transcendent. There is also a better sense of space and definition. Bass performance is in a word, incredible. Not only control but placement in the recording space, much better than the Transcendent. This isn't really a fair comparison since the Transcendent is less than half the price. But to these ears the Berning beats the hell out of any transformer coupled amp I've heard. The Transcendent does too, within its power limitations. It is just that these designs are faster, more resolving and natural sounding.

There are varying opinions about the Berning on some stats, especially at the frequency extremes. This in comparison with other OTL's. With the benign load of Merlin VSM-M's the performance is stellar.

I'll just go on believing that it doesn't get too much better than this. Ignorance truly can be bliss especially at this level of performance.

Jtinn, your comments are appreciated but in my opinion are quite closed minded about this amplifer design which eliminates the need for an audio output transformer, hence "OTL". Sure, not OTL in the sense of the some 50 year old school of though about OTL tube amps but an OTL design nonetheless.

Please keep in mind this is a new kind of OTL amp design which requires the old school thought of conventional OTL designs to be tossed out entirely and a new sophisticated one to be layed out on the board from scratch.

Anyone want to compare the old school OTL with the new school OTL directly? Please come on by, I'd put this 270 against any other 70W OTL on the market today.

Chris

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.