Why no threads on OTL amps?

Cool post, Tubegroover. All modern OTLs take the music one step closer to the truth. One comment I would make about the load stability is that the large number of tubes is also an attempt to lower the output impedance of the amp, not just current drive. The output impedance of the Berning amps is 2ohms or less, depending on model. And this is the case with relatively few tubes. This is the real breakthrough in the design in that the RF carrier system replaces the output transformer's task with a much higher turns ratio than possible with iron. Thus allowing fewer tubes, better efficiency, less heat, and a lower output impedance than previous OTL designs. And, it's not really in the signal path, just carrying it. Grid drive. Not cathode follower or circlotron. All new. With previous OTLs, damping factor was a problem because the amps output impedance was high enough to sometimes be above the load impedance and damping was seriously compromised.With a 2ohm output impedance the Berning design breaks new ground with respect to damping and does so with few tubes. In fact, in my MicroZ OTL, the output tubes are 6sn7's. Normally a preamp tube, and a great one. Tube heads out there know that preamp tubes are generally much more linear than power tubes. This is really the first time a linear tube such as the 6sn7 is actually driving a speaker directly. It is amazing. And very short signal path, too. Detail is dramatic. Midrange is liquid, and bass is fast and solid. The sound is balanced from top to bottom. If you just take the sound, not the power level, it is the equal or better of anything there is. I can't believe that I could afford such a thing, but here it sits - all 4 pounds of it! Must be a dream. David Berning is a genius to have thought up this level of tube "groovosity."(As Harvey aka Dr Gizmo, called it)

I agree, OTL is where its at.I hooked up my Futterman design NY labs amps to a pair of 15" Tannoy dual concentrics I picked up at a garage sale two years ago, and could not beleive what I heard, amazing natural music, I relax when I listen to MUSIC, not HI-FI.I put away a pair of Quad 63 US Monitors,and a pair of Magneplanar Tympanis and just listen to a pair of 40 year old speakers. By the way the Tannoy speakers are 15 ohm.There is some serious synergy between amp and speakers. I would love to hear from others using same/similar gear. Tubegroover is right, OTL is where its at.

I also own a Berning amp. I used to be a solid state kind of guy until having an epiphany regarding OTL tube amps. I listened to an Atmosphere amp and was blown away. I started researching OTL amps and became interested in Berning amps because of their novel technology. After listening to ZH270, I bought it. I recently changed to horn speakers and didn't need the power of the 270. So I sold it and purchased the 811 ZOTL. It has all the attributes of an OTL amp; clarity,speed,soundstaging, along with the SET midrange magic. I prefered the sound of the 811 over the 270. I think it has something to do with it being Class A with no negative feedback and single ended (unlike the 270).

Jayarr,

Which horn speakers did you settle on? I own a Berning 270 and am myself interested in horns. Did you try the 270 with the horns before selling it? How did it sound?

Thanks.

Kenl,
I have a pair of Avantegarde Duos. I found that I needed the integrated subwoofer to really enjoy all types of music. I didn't like the single driver(full range) speakers--no frequency extremes tho they do midrange very well. As to the amps, I did compare the two. The 270 sounded great but in comparison to the 811 was more OTL-like e.g. faster and slightly harder sounding. The 811 had slightly more midrange bloom but most importantly for me was that I started listening to the music and forgetting about audiophile sonic attributes like soundstaging,speed,
detail,etc. With the 811 the speakers completely disappeared. Hope this helps.