Otl's with AvantGarde Duos?

Hi Jayarr, FWIW, the Berning is not an OTL. There is a lot of misconception that it is, but it is just that.

An amp that uses an output transformer (air core or not) and semiconductors in the output section does not qualify as an OTL. Unquestionably an innovative design, but it is more accurately described as a Zero Hysteresis Loss amplifier, owing to the fact that there is no hysteresis loss in the output transformer. A true OTL has no output transformer at all and is all tube.

I am afraid that Atmasphere does not quite understand the Berning design, yes, it's not a 40 or 50 year old "OTL" design, but since the transformers and semiconductors are not in the audio frequency signal path, then it's irrelevant if they are there.

This amp is really beyond the normal OTL, which is why Berning named it ZOTL.
The Berning amp is ZOTL and is all tube, completely transformerless and semicondutorless in it's audio signal path.

I think, even with OTL designs it's the same like everything else.
Some are better than others, work better or whatever.
I own OTL's but please can someone describe the "sound " of OTL ?
I use OTL (Atmasphere M-60II ) with a horn loaded design, 99db, 8 ohms and it is excellent. I use Pass aleph's, too and my OTL have no "sound". They amplify the signal the way it should be. Maybe they are much faster than regular tube designs, what they definetly own, is a excellent high frequency area, but that's the way it should be.
I know some AG's and like them, I don't own them, but listened a few times to them, I would use them with OTL without hesitation.

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.