The End Of Big Iron?

I went from 100wpc tube amps to a pair of D-Sonic 600w mono amps after my power regenerator murdered them one fine morning. At the time, I was running 86db Snell speakers that I had bought with the amps back in 1991. I expected the new cheap class-d monos to be a serious setback compared to the Atma-Spheres, but elated when they turned out to be good as their generally HT customer base rave about, but it took me a long time and a lot of tweaking to get them to really fit well in my 2 channel system. But, with the right power cords and some reasonably good support under them, they can sound superb. These amps weigh about 10# each and are the same size and shape as a shoe box yet are capable of great things when the upstream system is singing sweetly.

I have no intention of comparing them with the Atma-spheres at the time. I have made scores of changes to the system since then, many of which would also have improved the sound of the OTLs as well, and if I ever find a few thousand "extra" dollars to have them repaired, I may put them back in service during the Winter months, but in the mean time, I'm not missing anything.

Just one last thought about the efficiency of the class-d amps. I calculated the energy cost savings for the 2 years following the change from tube amps. It was costing about $80/month for electricity to power the amps and another $50/month to run the air conditioning in the not-winter season here in Wisconsin.

Mcbuddah, what is wrong with your Atma-Sphere amps? Bad tubes?

A simple and inexpensive means of dealing with hot amplifiers, tube or solid state, is to install ceiling ventilation with ductwork to move the warmed air out of the building. This is very cheap to install and costs very little operate and is very effective! Air conditioning is rather brute-force.

"A simple and inexpensive means of dealing with hot amplifiers, tube or solid state, is to install ceiling ventilation with ductwork to move the warmed air out of the building. "

Installing new duct work is simple?

I guess its all relative.

Mapman, letting the heat coming off amplifiers escape to the outdoors can be extremely effective. Whether that requires ductwork depends upon the construction and what systems are in place. In other words if you are able to remove the heat there is no need to cool it, but you will need to make up the volume of air removed somehow.

My room with the big Sound Labs is pretty large. The Atma-Sphere MA-1s or MA-2s are perhaps fifteen feet away from the listening area, so the heat has some distance to travel, in which it blends with the room air. Although it is noticeable it's not bad. The HVAC system is generously oversized, so even with the big amps going and a dozen people listening, it's all good.

Mcbuddah, since you're in Wisconsin you might want to stop by one day for a visit. I have the M-60s in the downstairs system (essentially the system we showed at AXPONA a few weeks ago) in the much smaller room, and it's a very liveable, cozy and relaxed listening room.

Ralph, I actually retired as a HVAC technician and so did learn to calculate room heat gain/loss as well as measuring current draw. When the amps were in service for the last few years, they were located too close to the house's only thermostat and routinely caused it to read up to 10 degrees(f) higher than ambient temperature only fifteen feet farther away. The whole issue would be moot if they were still working, as I have just finished a major remodeling project in which my wife agreed to let me swap locations with the HT system and now have quadrupled the room square footage far away from the thermostat.

As to the problem with the amps, they both went bad within minutes of each other. I suspect that they were murdered by a malfunctioning PPP regenerator unit that also died that day. I believe that its AC output stage went bad and created some kind of uncontrolled, clipped signal instead of the nice rounded waves it is designed for. The fireworks happened shortly after powering up the system normally. After 20 years with them I had a routine for startup and put them in standby for an hour while warming up the Thor phono stage. The preamp was a Classe DR-6 that was always left on, so there could not have been a problem with a failure to turn the gear on in the right sequence. After cueing up the first record of the day, I noticed that only one channel was playing so I moved behind the errant speaker and reached for the amp's off switch while the good side played on normally. Before I could switch it off, several of the power tubes went bright orange and one exploded. About a minute after switching it off, the other side started the same fireworks show and there the PPP shut down, dead as a stone.

The reason I decided to replace them with the class-d amps rather than sending them back to you was purely economic. I loved those amps since I bought them from Bruce Jacobs 25 years ago. But, my income has gone down with retirement and I hoped they might not be too bad for the money I had. I figured that repairs would need at least $600 worth of new tubes, $100 for new packaging to ship, $$300 for 2-way shipping, I would need more than a grand just to get started. I guestimated that each amp would need at least $1500 to fix and that put the repair out of my reach. Fortunately, the D-Sonic amps have proven to be over achievers for their price.

Now, a few years down the line, I have a bit more income and have made scores of changes to my system and hope to someday have the Atma-Spheres fixed. I know in my heart that they would glorious in the configuration I am putting together.