Atma Sphere

You might try making the same post at http://www.otlamp.com/ which is the website for Atma Sphere owners. I am sure someone there will give you the appropriate feedback on your question.

Happy Holidays,

Scifi

I have M60 II.2's and use only half of the output tubes since 30 Wpc is okay for me. Not much heat--no problem with the amps sitting behind the speakers a fair distance away from the listening area. Of course there would be more heat with all eight output tubes. You have to balance them and adjust bias once in a while, and need a multimeter ideally since the built-in meter is said to be poor, and that's probably beyond the capabilities, and also not to the liking, of a nonaudiophile. But hey, that isn't you, is it? After all, you posted this query on Audiogon.

The Atma-Sphere amplifiers are totally stable and absolutely reliable. The output tubes are very rugged tubes and will run for a long, long time. When replacement time does come, they are not terribly expensive and they do not have to be matched. A-S sells them at very reasonable price.

The bias on the amps remains very stable, in my experience. Over the first 30-days, you will need to monitor/adjust it every few days, but once it settles in, it will stay very stable.

All of the Atma-Sphere amps operate in Class A. Any output device run in Class A, solid-state or tube, throws off a fair amount of heat. How much heat depends on which model amp you're talking about due to the varying number of output tubes. The M-60s are modest heat producers compared to the MA-2s. The MA-2s, which I own, will definitely warm up a room.

I agree with the recommendation to visit the Atma-Sphere Owner's Group web site, www.otlamp.com The folks who post there would be happy to answer other questions you may have.

Depending on which amp, i.e. the larger number of output tubes used, the hotter the amp runs. I have the MA-2's which consists of twenty 12AS7's per mono-block. Hot, at times, is an understatement. I live in Wisconsin, so a good portion of the year temperature is a non-factor. The only other A-S amps I have heard are the MA-1's. Fewer tubes, less power, less heat.

Regarding tube replacement, the drive tubes, 6SN7's have a reputation as long running, consistent sounding and reliable; especially NOS. The outputs....not so long, but not all that expensive.

My amps, nor the other two I have personal experience with have ever had reliability issues. Do take Scifi's suggestion and research either ASOG or threads on Audio Asylum.

The amps are very impressive. Well worth investigating.