Tube amplifiers that really drive MBL 101E's

My understanding is that the MBL 101E presents a pretty flat 4 ohm impedance curve. It dips just below 4 ohms in the midrange and then rises in the lowest frequencies (good for OTLs).
There aren't any big impedance swings on the graphs that I've seen.
The Atma-Spheres are incredibly easy to use and they are bullet-proof. Heat can, however, be a concern.

Oh, I thought they dropped off somewhat in the lower frequencies in the 20hz and lower region but I could be wrong. Depending on the output impedance of the OTL, the flatter the speaker impedance, the better for the amp, any swings can cause some OTL's to act like a tone control, in more difficult loads, cause them to oscillate, which the Bernings are not prone too.

Ease of use of course is subject to interpretation, true auto bias (60 times a second), brown out, surge, short and DC protection, all auto correcting and not to mention decades on tubes.

We had a gentleman send us back a amp we made in 1975 just for a check up, still with the original tubes, checked out fine and shipped back with the same tubes, that's our interpretation of bullet proof :)

Vetterone should have his amps in the next couple months, keep in touch with him and see what happens, maybe you can fly out to his place.

The MA-2 is full power to 1 Hz. The impedance curve of the MBL has no severe dips and is actually an easy load as far as the MA-2 is concerned.