After about 48 hours of burn-in, I sat down for some critical listening this afternoon. A few caveats first. My baseline is the existing system with D'Agostino M400's. These were incredible amps that gave me a beautiful, lush, detailed presentation in combination with the other components in my system. I'm going to describe the differences I hear between that baseline and the system with the MSB mono's. There are so many variables (room dimensions, treatments, cables, speakers, front end etc.) it would be tough to draw any conclusions on what they would sound like in your set up.
Nonetheless, the MSB's are very special amplifiers. The initial impressions I had when I first turned them on have been confirmed and reinforced. The backgrounds are blacker than black. This has the effect of making every voice and image more pronounced. I also find that I can listen at a louder volume without fatigue. We set the gain on these to MAX for now and I will experiment by backing off as time goes on. Right now, the normal listening level as shown by the MSB volume level is the same as it was for the D"Ag's.
The second characteristic I noticed is low level detail. The background instruments deep in the soundstage or off to the right or left now have the texture and definition of the main images. Detail in general is off the charts even compared to the D'Ags. It is especially pronounced on percussion instruments. Piano notes have faster attacks. On xylophone, you can separate the thump the hammer makes on the key from the actual note. I have on file from a Chesky CD with a bluesman playing Bones. The sound of the woody impact is scary realistic.
The MSB's soundstage breadth and depth, bass definition (particularly on acoustic bass) and tonal accuracy all edge the D'Agostino's but not by much. Their accuracy and detail are what separate them by a wide margin.
The amps after running for two days are no hotter than the D'Ags were after running for an hour. The engineers at MSB did a great job of thermal management.
In sum, I'm very pleased with the purchase. My ears are no match for a professional reviewer or for many of you. I only know what I like when I hear it in my room, with the rest of my gear with my files. These amp I like. A lot. I've had Krell amps ever since the KSA-250 back in the 90's. Sad to say goodbye but the MSB's are the new stanadard for me.
Eric