Atmasphere amps trustable?


Tube world, a big world, then I came acorss the Atmasphere on the net, looks different from those common tube stuff... kinda weird, the M-60 uses 8x 6AS7G output tube and 4x 6SN7 driver tube per channel, where're the rectifier tubes? Plus they're so-called OTL, sounds even more weird.
mtoc

Showing 2 responses by rlawry

Back in my earlier and more adventurous days I bought a pair of Fourier Systems Panthere monoblocks, those with 8 of the Russian military triode 6C33CB tubes in each chassis.  They were based on the original Futterman design and were different than anything I tried previously or since.  They powered my Wilson Audio Sophias with an enormous soundstage and unmatched transparency, but did not have that lean, hyperdetailed, small-image sound that most other amps have.  I would characterize the images as "diffuse".  Using a pair of autoformers helped also.  However, in addition to doubling as space heaters, drawing 5 amps at idle, they were absolutely unreliable.  Sometimes one channel would go down, popping out a little male-shaped red circuit breaker in the back, while on other occasions they sounded less authorative and a check of tube fuses would show several were blown.  After investing in Buss fuse company stock I contacted Ralph Karstens and he offered to refurbish the amps but graciously suggested I clean and re-tension all of the tube sockets as they are tempered by the prodigious heat thrown off by the amp.  So I had a backyard project with the amps disassembled and parts all over my patio furniture, not to mention an exasperated spouse.  I then took it to Brooks Berdan and their technician replaced some diodes and other things I don't understand, and the amps then did become reliable.  However, the damage was done and I no longer trusted them and sold them to get something much more reliable.  I have never heard nor seen in person any Atma-Sphere equipment, but I did look into these and understand they use a different circuit called a Circlotron which is apparently more reliable, but almost certainly sounds different.  I have thought about matching these with my single-driver speakers but reluctant to do so based on previous experience.
I stand corrected.  My OTL amps were indeed produced by Fourier Components in the late 1990s.  BTW, to my knowledge, Atma-Sphere is one of the few, if only, OTL amp companies to survive for any length of time.  Probably a testament to their reliability.  Most of the others, NYAL, Futterman, Fourier Components, Counterpoint, Silvaweld, Prodigy, for example, have gone bankrupt.  I sense a trend here.