Hi Peter (Csontos),
First, let me repeat what I said:
I wouldn't be surprised if the sensitivity increases by 6 db (i.e., you would have to reduce your volume control setting by 6 db, to achieve the SAME VOLUME [emphasis added] as in stereo configuration)
You then asked, in part:
Won't an amp making three times as much power produce at least 4-5 db more spl at the same volume setting ....
Our two statements seem to me to be perfectly consistent with each other.
The rest of your sentence was:
... with the 'same' sensitivity?
If sensitivity is considered to be the input voltage required to drive the amp to its maximum power rating, whatever that rating may be for the specific mode that is being used (stereo or bridged mono), then the amp's sensitivity would probably be the same.
But my interpretation of the intent of the OP's question about whether input sensitivity would change is that he wanted to determine if there would be a significant change in output power for a GIVEN input voltage.
You have found that to be the case with your Acoustat amps, and I was saying that I wouldn't be surprised if it were the case with his Classe amp.
Whether or not that increase in output power and volume for the same setting of the volume control is considered to be a change in "sensitivity" is a matter of semantics and definition. I chose not to get into semantics and definition, but to respond to what I perceived to be the intent of the question.
Best regards,
-- Al