Atma-sphere 3.0 to 3.1

These were originally Mk 2.3 that had been back in the 18 to 24 month window for upgrade to 3.0. They are MA-1's as well. I do not know the history of the Class A/AB switch on the various models. The upgrade from version 3.0 to 3.0 was significant according to Ralph and the amps confirmed that upon their return. Just do it.;-)

Yup!
MA-1's though. Much lower noise floor, now they are essentially dead quiet with no preamp signal. Slightly better imaging and detail. It is, IMO, a worthwhile upgrade if you can do without them for a couple of weeks.
Mike

I believe that most of the updates reside in the PS and on mine they removed the Class A/AB switch.