Otl's with AvantGarde Duos?

Allanbhaganinfo, you might do as I did and read the following patent at this link:

http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=/netahtml/srchnum.htm&r=1&f=G&l=50&s1=5,612,646.WKU.&OS=PN/5,612,646&RS=PN/5,612,646

you will see that the title is misleading, as in the first two statements is mentioned a DC to DC switching power converter (solid state) and and output transformer.

Use of both of these technologies in an amplifier excludes it from being in a class of amplifier known as OTLs. This is a simple fact: you cannot have it both ways (call it an OTL and then have an output transformer as an integral part of its operation).

I read this patent some years ago. Sorry to have to correct you on this, but as you might expect it is my area of expertise, that is if one were to construe that I have an area of expertise at all :)

There was a bit of debate in POSITIVE FEEDBACK magazine regarding this issue some years back. To this day, it still amazes me that David continues to call this amplifier an OTL when he clearly knows it isn't (if you refer to PF, you will find that he admitted such in that magazine, but found that people asked less questions when he described the amplifier as an OTL). If it were me, I would have described the amp for what it is: a unique means of coupling tubes to a loudspeaker that represents a new type of amplifier. ZOTL is misleading, as the moniker has no meaning. ZHL amplifier might be closer, as Zero Hysteresis Loss more properly describes the advantages of the output transformer in this design.

As I said, I am afraid that Atmosphere really does not understand this technology at all. There are no Audio output transformers or Solid state audio output devices in the ZH-270, NONE.

I am sure your expertise is in OTL's but the ZH-270 is again way beyond that simple terminology.

It's simply a way better design than normal OTL designs of the past.

Allanbhaganinfo, you seriously don't get it, do you?

And Ralph was being so polite...
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It seems to me the primary goal of an OTL is to eliminate hysteresis loss and bandwidth limiting imposed by output transformers. Since David Berning's patent is about another approach to achieve that goal, may I suggest that the results are all that count. In the conventional sense Ralph is right, but it may be irrelevant if someone is able to invent a better mousetrap - but that's not to say the other is. An amplifier with zero hysteresis loss between the output tubes and the binding posts by virtue of no iron in the signal path and no output transformation in the audio band can, in a practical sense, be considered to be output transformerless due to the same benefits it delivers. Just my opinion, sprinkle liberally with salt, film at eleven, etc. Bottom line, use your ears to see which you prefer. Both are outstanding amplifiers.

Brian

Rushton, sorry but you are right, I don't get it!

Please explain.

I was equally polite in showing Ralph that he's not right in his terminology of the Berning design.

There is much, much more to it than that.