Why no threads on OTL amps?

I think any mid to high-efficiency speakers (i.e. 89db and up) with 8-ohms (nominal) impedance will work just fine with most OTLs. Unfortunately too many of the popular high-end speakers tend to work at much lower (4 or 5) ohms. I bet one reason for this is, most people end up buying high-powered SS amps over OTLs or even SETs. I own a low powered (20 wpc) Graaf GM-20 OTL -- my speaker choice was a pair of Kharma Ceramique 2.2 over more the popular Wilson Watt-Puppy.

Well there have been threads on theses marvels but there doesn't appear to be too much experience. Many steer clear of tube amps because of the hassle, an OTL even more so because of the heat output and the impedance restrictions with perceived reliability issues in hot pursuit.

With the right amp to the right speaker, isn't there always a catch, there really isn't anything NOT to like. To me, at their best with the proper load they are the ultimate, a conjoining of the virtues of both ss and tubes that being speed, clarity, presence with incandescent highs and very well defined controlled bass comparable to the best out there. The key again is amp/speaker interface.

Chris is right on concerning the incredible Berning ZH-270 OTL amp. I bought one used about a month ago and am astounded at it's sonics and capability.

I was a little apprehensive about it's ability to drive my Aerial 7b's. These are not considered tube-friendly, being 86dB, and 6 ohms with a wide impedence swing. But to my delight and surprise, it doesn't seem to have any problem with them. The Berning can drive them to very high levels in my 20 x 21 x 10 room. I have a combined 2-ch/HT system, and use the Berning not only for 2 ch listening, but for HT on my L/R front speakers as well. I know you'll find this hard to believe, but it handled the opening battle scene on the Gladiator dvd better than my EAD Powermaster 2000. And it's got 400 watts x 5 channels compared to the Berning's 70 watts.

I've got a REL sub connected to the high level input of the amp. During the most dynamic sequences on the dvd, the EAD would shut down due to the low impedence of the combined load of the REL & Aerial's. The Berning didn't miss a beat. It delivered all the volume and impact you'd want. Simply incredible.

I'm now considering selling the Aerial's and replacing them with a horn speaker. I'm told there's nothing like a "good" horn to bring realism into the listening room. While the Berning will be overkill from a power standpoint, I feel confident it will deliver sound to die for.

This is not a well known amp. The only reason I was aware of it is because two of my friends each owned one, and kept telling me how great it was. I forgot to mention it's versatility. It's got 2 RCA inputs, and a quality volume control. This allowed me to run both my cdp and front HT channels directly to the amp. It's got more than enough gain for both. I'm now debating on whether I need my Joule Electra preamp.

For a small 10 lb amp to deliver this kind of performance and versatility, not to mention the 10-20 year lifetime on the tubes (it's already got 4 years on them and going strong) it's a miracle product. If you get the chance to pick one up, don't let it pass. You won't regret it.

Tacs-You'd need a lot more then 30k for your dream system, the amps alone are $19,995 per pair. I have spent a good deal of time listening to these amps on a good friends system and they are as good as everyone says, perhaps better. OTL's are incredible, though they have there set backs, for me its cost!! other then that I would have them.

~Tim

oh and btw I concur with both Chris and Ken about the Berning. You WILL be amazed at its sound, versatility, price and weight/performance. The hardest part is just getting past the small size. Then you listen, no way man, how'd Berning do that? The zhotl is the latest incarnation of "the little engine that could".