I have quite a bit of experience with the David Berning ZH-270 and I whole heartedly agree with Thorty40. From reading all of the posts on this thread, one of the biggest concerns with OTL amplifiers is there ability (or in some cases inability) to drive certain speakers due to impedance requirements. Just in a technological aspect the Berning is different from ALL other OTL's. The Berning is based on an impedance matching system which automatically matches the output impedance with that of the speaker. So it then all comes down to power requirements. The Berning creates 70 of the most powerful watts I have ever heard. Of course there are just some speakers that will just suck the life out of this amp, but not most. As far as sonics are concerned this amp is truly special in many ways. I have never heard an amp with more inherent speed and control over the music. Period. The midrange is silky smooth and more alive than I had ever thought possible from an amp, with highs to match. The bass is something which, put simply, must be heard to believe. If you think that tube bass can't ever match solid state, be prepared to be disappointed. I have owned many solid state amps and the bass can not even compare to the Bernings. All of the other OTL's mentioned above are all very respected names, and I am in no way implying otherwise. What I can tell you is that the Berning is a new kind of OTL which does not suffer from some of the problems that the aforementioned amps do. Put simply the David Berning ZH-270 is the most sophisticated amp in the world. A stroll through the David Berning website will confirm this as there are not many designers who can even decipher Davids theories and topology schematics. The Berning tips the scales at a mighty 10 lbs., runs cool enough that you can place your hand directly on the amp anywhere, indefinitely. Idles at one hundred watts and has a peak consumption of about 300watts. And yes, it only uses 4 output tubes! The most striking quality though, is the amps ability to effectively match the impedance of the speaker at any given time. It does all this, while maintaining a superior musical quality which at times is truly hypnotizing. By the way the Berning automatically bias's tubes on a cycle by cycle basis at all times. If you are in the market for an OTL amplifier(or any amplifier for that matter)make sure to put the Berning on your very, very short list. The Berning is an investment which will give its owner many years of enjoyment(there is a manufacturer claim of 20 years on the tubes)which will NEVER disappoint.
