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Original Message
RE: Atmasphere MA-2 impedance question
Posted by Lew on June 2, 2012 at 06:32:02:
Are those the numbers after you installed the Australian 90:1 transformers and removed the parallel resistance, along with the rest of the components of the hi-pass filter? If so, fear not. The efficiency is so much higher without the parallel resistor that I am sure 50W would do. My Atma-sphere MA240s don't make much more than 100W, and they are sailing with ease when I now run my 845PXs. In any case, and to answer your question, these amps are quite comfortable with those impedances; there may be a small loss in efficiency at 59 ohms, but it's nothing to worry about. (I will leave that to Ralph.) You're probably getting on average MORE power, lower distortion, wider bandwidth, at these impedances than what you can achieve into 8 ohms or certainly anything below 8 ohms.
The data you give sound like the measurements I made on my own 845s after I installed the AU transformers; perhaps you are reiterating the data I put up on SLOG.