Volume level mystery - can you solve it?

I recently replaced a pair of Linn LK power amps (85 and 140, in passive biamp mode) with the much more powerful Linn 2250 amp (just one). My preamp is a Linn Kairn. I have noticed that in order to achieve the same volume levels with the 2250 as I was getting with the 85/140 combo, I need to crank the Kairn volume setting much higher. By way of example: on a scale of 1-100, 50 used to be my normal listening level, but to achieve that level I now need to turn the Kairn up to 70 or higher. The Kairn only goes up to 100, but with the new amp, everything below 60 or so is very, very quiet. After 70, the volume ramps up pretty quickly, whereas with the 85/140, the distribution seemed more of an even straight line graph. Does anyone have any idea what this is all about? Are amps just calibrated differently? If anything, I would have expected the 2250 -- a more powerful amp -- to produce higher volume at lower settings, but the reverse seems to be true. Any thoughts about this would be much appreciated. I am a little worried that something is wrong with the amp, but aside from the volume issue the sound seems good. Thanks.
Gunbei, I no longer have my old amps, but wouldn't higher impedance require turning the volume up higher on the preamp?
Ahhh, too bad.

I'll throw out some hypothetical numbers here just for the sake of illustrating an example.

Say, one of you old amps had an input impedance of 47Kohms and the other old amp you were combining it with had an input impedance of 23Kohms. Your preamp would see them as 70Kohms. But if you reconfigured your set up so you were just using a single amp with 47Kohms or less, this new amp might require more gain to attain the same volume levels as your two older amps being used together.
One other possible solution to the mystery: from looking at the owner's manual I see that there is a small button on the back of the unit that switches from balanced to unbalanced. I have cabled the unit for unbalanced, but never checked to see what position the switch was in (because I doidn't notice it). I am not at home to check, but i wonder if this could explain the problem.
Kdl6769..The little button is your problem for sure. When an amp with balanced inputs is operated single ended the
(-) pin of the input connector must be grounded. That's what the switch does.

Gunbei...When the two amps are both driven by the preamp, the combined input impedance goes down, not up. For example: two amps with 20K would be 10K. Actually, cutting the impedance in half like this might not make much difference if the pream[ is low impedance, and can hold the voltage up dispite the increased current needed.
Really Eldartford? Ooops, I'll keep my mouth shut from now on when it comes to the technical aspects, heheh.