Why no threads on OTL amps?

Twl-When you think of SETs you think of the late Gizmo Harvey Rosenberg of NYAL's fame. He went absolutely bonkers over the Seigfried and the zero hysterisis technology in general. The ultimate realization of tube technology today must include the Siegfried with either the 300b or 811 triode. Imagine a low powered SET that isn't limited to that magical midrange but expands its performance into the high and low frequencies as well. Regulated switching power supply and an OTL output stage, dead quiet, auto biasing, reliable, low heat and elimination of transformer related distortions. Where do you go from there? I guess it can be refined but in reality Berning has established a new path and there seems to be a hush over it in the audio community. I haven't heard this amp yet but can only guess that it sets new benchmarks for SET design and may be near the pinnacle of reproduced audio with the right speakers for those looking at this approach. There is much to be said for low power and highly efficient speakers. The zh270 itself is so incredible that you really have to wonder about the advanced level of design and engineering in these special products. I haven't stopped wondering since I got mine over 2 months ago.

Kris: Your statement of "The Berning in my opinion bested the Tenors in every way. Speed, clarity, bass, and of course that magical otl midrange", is quite a reach considering you were listening to two entirely different systems. That is like listening to a system in Montreal and saying did you hear how good those power cords were? It just is not a real valid statement.

Since I have not heard the Berning amps in my reference system, I will not make any statements as to whether they are good or bad. It would be impossible for me to do so with a clear conscience.

The Tenor amplifiers are the finest amplifiers I have ever heard. Nothing I have heard is even close and that is why I took on the line. The Tenor's can handle impedance swings as well as any OTL. What they do not tolerate is what any 75 watt amplifier would have a problem with, inefficient speakers. I have had them on 86 db Eggleston's and they do great within a reasonable limit. If you are looking to drive an 80-86db speaker at over 100db, these amplifiers are not for you. I know at least two people driving Watt Puppy 6's with a pair of Tenor 75's and they could not be happier. The 6's are a 4 ohm speaker that drops to about 2.

Twl: Your statement of "I'll bet it will squash the Tenor amps flatter than a pancake" is quite funny and I will be happy to take that bet anytime you want. How much money you have? :)

http://gallery.consumerreview.com/audio/gallery/files/TWINSOTL.asp

"The Tenors can handle impedence swings as well as any OTL."

Not true actually, the Berning OTL's INCREASE output power into lower impedences. The Tenors cannot do this simply due to the nature of their design. This does not mean they are not great sounding amplifers, it just means they will have to struggle more with more difficult loads than a single ZH270. Lets quickly look at a couple specifications -


Tenor 75wi (monos) - @ 4, 6, 8 ohm - 55, 75, 75W respectively.

Power consumption - 730W (not indicated if this is idle or max.)

Berning 270 (stereo per channel) @ 8 ohm - 70W (84W output at onset of clipping), 4 ohm - 110W at onset of clippin.

Power consumption - 100W @ idle, 300W max.


I doubt the Tenors (or any other OTL) withstand less than 2 ohms or less for very long without losing steam, they were not designed to drive those difficult impedences with any consistancy. A ZH270 I know for a fact will tolerate quite low impedences for extended periods AND can provide much higher ouput power into lower impedences because of its unique ability to match impedence.

For example -

I personally heard the ZH270 drive a pair of Magnepan 3.6QR's LOUD with lots of drive tolerating some huge dynamic swings while playing some crazy techno music. For the kind of headroom we had one would think we were using some big solid state bruiser, but we weren't. We were using a single ZH270 with the difficult to drive Maggies.

Any 70W amp has its limits, true but we are discussing the subject of OTL amps specifically and I would welcome a friendly comparison with the Berning ZH270 and a Tenor Classic 75wi. I am confident a single 270 would do more than hold its own with the Tenors, especially with difficult to drive speakers like the Magnepans and/or ESL's for that matter.

Chris

http://www.condor-connection.org/slog/bbs/messages/422.html

This is an link to an image of a cutting edge, state of the art designed OTL amplifer made by David Berning based on ZH technology used on his current product line up.

As you can see by the internal layout, this is a radical departure from the conventional OTL technology based on Futterman principals some 50 years ago.

This mono block weighs 8 or 9 pounds and puts out 120W into 8 ohms and INCREASES output power into lower impedences.

Just for a minute, think of all the limitations and drawbacks associated with the current OTL amplifiers. Now think about one without these limitations, not possible? Incorrect, it is possible and happening right now.