Can my MC275 power speakers with 91db sensitivity

So, to be completely open kimono here, my experience that I refer to above is based on the following experiment. I would submit that this A/B test surpasses many in terms of relevance. That is, I speculate that many audiophiles compare memories of sounds of systems or components and in different rooms, dealerships, or other places. To be true, you have to minimize the variables and time between auditions down to minutes or seconds, NOT days or weeks. As an example, I read various audiogon members saying a certain CD player sounds better than another. I would place more trust in their assertions if they had both CD players attached to one preamp, simultaneously, with the same cables, with the same CD queued up and playing in time, to the same speakers, in the same room. I have done this experiment, many times, and I can tell you it is very hard to tell the difference. Otherwise, we are relying on memory, biases, and corrupted senses.
So, back to the discussion. I had my MC240 and C22 vintage equipment, which has been maintained, connected to a pair of B&W 804 diamond loudspeakers, source Oppo BDP95 from the RCA outputs. I had the same SACD/CD player connected simultaneously via the balanced outputs to a Bel Canto Pre2 preamp feeding an ARC 100.2 amplifier into the same speakers. To do the A/B, I would simply disconnect the banana plugs from one amp into the speakers to that of the other amp and play the same music from the CD player. Music from the CD player was in 15-30 second samples. So, the brain only had to remember sound from about 30 seconds ago, in the same room, with the same speakers, with only different electronics. Room was about 14x24x8 feet, perfect rectangle with only one open hallway (3 feet wide), system on the long wall, with basic treatment (curtains and no-name echo busters).
The differences were miniscule, with the only ones being mostly attributable to power - that is, at higher volumes the 100 w/ch amp could do better. Otherwise, both sounded very good and very similar. The only noticeable difference was that the ARC had better bass control over the B&W's than the MC240. The Bel Canto was also more transparent than the C22. The Mac combo vs the SS combo was just as good in the highs (treble).
So, this is but one example/experiment in terms of two different sets of electronics - obviously there are countless other components that one could purchase and do a similar experiment. The results I observed are but a small percentage of the possible outcomes.
Lastly, I would apologize for 'hijacking' this thread to get on the above soap box. But I think it is still relevant, in terms of when it is asked "can X amplifier power Y speakers", one notes that the room dimensions and characteristics of the components (efficiency of speakers, power of amplifier, etc,), type of music, and other associated audiophile pitfalls that I am trying to address here.

Jimmy, rather than composing what would be a lengthy and somewhat off topic response to your posts just above (with which I partially agree and partially disagree), I just want to make one point. Your test methodology was potentially harmful to the MC240, as it can be harmful to operate a tube amp having an output transformer without having a speaker (or, alternatively, a suitable load resistor) connected to it. Especially when a signal is being sent into the amp, as was the case here.

The reason is that "inductive kickback" occurs in that situation, which can result in damage to the output transformer and/or the output tubes. Google that term for more info.

Regards,
-- Al

I owned both and I still say if you want good SS get a Mac275...

Al, I have a quick question about "kickback inductance." On rare occasion, I switch back and forth the hot speaker wire between the 4 and 8 ohm outputs taps. The time interval of a "no-load" condition is less than a second. When doing the switch, I mute my linestage to ensure a signal is not being sent to the amp. Could a short interval open circuit of that magnitude damage my amp?

The reason I don't turn the amp off before switching the taps around is because I am reluctant to subject the amp to frequent off and on recycling.

Hi Bruce,

I can't envision any way in which that might cause a problem. Inductive kickback occurs because the voltage across an inductance (in this case, inductance in the transformer) is proportional to the amount of inductance multiplied by the rate of change of current. A very abrupt change in the amount of current flowing through an inductance can result in a VERY large voltage spike, albeit a brief one, if the energy has nowhere to go. If that spike occurs in the transformer secondary, it can result in an even larger spike in the primary, due to multiplication by the turns ratio of the two windings. But without a signal being present, none of that would happen.

The one exception I can think of to that (which doesn't apply to your situation) might be if the amp were turned on or turned off without a load being present. In that situation an internally generated turn-on or turn-off transient might conceivably be large enough and fast enough to constitute a potentially damaging (or long-term reliability degrading) "signal." But even that would seem to be unlikely in most (but not all) cases. One situation I can envision in which it MIGHT be a problem is if the amp has a B+ relay which abruptly turns on plate voltages to the output tubes some seconds after turn-on. That would result in an abrupt change in the amount of DC current flowing in the transformer primary.

Best regards,
-- Al