I dont think vibration is an issue with the DK amp. It is a very massive peace of equipment and there is no vibration to speak of. This brings me back to the EMI issue. The concept is quite simple, some of the EMI bounces off the aluminum cover and goes back into the circuitry, creating a sort of a negative feedback circuit. When a small amount of signal goes back into the circuitry it gets amplified again. This is the reason I believe the amp sounds better with the cover off.
What I hear is that the midrange becomes even more open and organic when the cover is off. There is also a bit more detail and texture in the bass.
What I hear is that the midrange becomes even more open and organic when the cover is off. There is also a bit more detail and texture in the bass.