Thought on OTL tube amps

I have also owned and auditioned a variety of amps. Solid state; Classe, Krell, Gamut, Plinius, Threshold... Hy-bred; Lamm... Tube; Jadis, Lectron, Conrad Johnson, Convergent Audio... OTL; Atma-Sphere, Joule. I have found, as with nearly every piece of audio, gains and concessions in each approach. Presently, I find the Joule amp to be fantastically musical, yet capable of reaching the frequency extremes. Bass nearly as deep as Classe and Krell with greater body and density, shimmering highs, plus a near CAT midrange (not quite as lush as the Jadis amps). These amps, both the A-S Ma-2's and Joule Rite of Passage, have adequate power to drive the power hungry Avalon Eidelons to a very high listening level, which I require.

I will respectfully disagree with Jallen regarding damage to speakers from blown out tubes. With both the A-S and Joule amps the internal protections have arrested any harm from reaching the drivers on my speakers. I too witnessed removal of an output tube from an MA-2. Not to be done on the Joule, though. The Rites of Passage require all output tubes for proper function.

I have much enjoyed the few solid state amps, especially with tube preamp, but ultimately found the midrange less fullfilling. The Jadis along with the other tube amps left me wishing for more slam and top extension, although they likely would have benefitted from additional tweaking.

The OTLs have come closest to achieving what I demand from the particular system I now own. Do keep in my mind, they run very, very hot and devour electricity. Certainly more than any other amp I have owned. As is typical, the associated components, listening space, and your tastes will best dictate whether these amps prove satisfying.

FWIW,I've owned an Atmasphere S30 for 10 years almost since it's introduction currently updated to the latest 3.1 configuration.
Over that time there have been no significant mechanical/reliability issues. IMHO, these "OTL concerns" date back to the Futterman amps and their clones. Unfortunatly, modern day OTL manufactures are unfairly lumped in with them.
AFC, I have not heard the ZU Essense but on paper it's a match made in heaven with the S30. With the Zu's minimal crossover there would be very little between the output tubes and the Z4 driver except the speaker wire.
Have fun.

There are some very nice options to choose from on the OTL amp market these days. Atma-Sphere, Berning, Joule Electra, and Transcendent Sound to name a few. All of which are very reliable. It's rumored Roger Modjeski at Music Reference is working on a new OTL design. In addition, there are some great speakers that are OTL friendly, including Merlin (Bobby P. uses a Joule Electra set-up at the audio shows), Zu, Audiokinesis (Duke uses Atma-Sphere at the audio shows), Classic Audio, and Tonian Labs.

I myself own an Atma-Sphere S-30 that I use with my Audio Kinesis Jazz Module speakers. The S-30 was actually used to voice the speakers. I also own a Berning Micro ZOTL which although 1 watt, can drive my Tonian Lab TL-D1 speakers nicely in my small room.

Thanks all. What are the purported advantages of OTL amps over those with transformers, aside from eliminating possible transformer hum and obviously making the circuit more "pure" in a sense? Hum isn't an issue with the MastersounD or the Frankensteins I have. I'm just looking for ways to get different sound, see what I prefer with different types of music.

Anyone have any experience with McAlister amps? Plenty powerful, and a unique build, using old television horizontal sweep tubes rather than standard power tubes. Claims to greatly extend tube life, since the old TV tubes tolerate much higher plate voltages than do standard audio power tubes. They also have one that's tremendously powerful- 195 watts per channel. Pretty salty for a tube amp. They also have a very, very attractive price point.