Ditto to what Atma-sphere wrote. Chakster, the Krebs mod is to stabilize the stators. As you know, in a DD, the platter is generally the rotor of the motor or is affixed firmly to the rotor assembly. In the case of the Mk3, a gigantic ring-shaped magnet is fixed to the underside of the platter, so the platter IS the rotor. When the motor spins the platter, there is an equal and opposite (in direction) force applied to the stators. Any movement of the stator assembly in the direction opposite to that of the platter can at least hypothetically cause the servo system to "think" there is a speed anomaly that it needs to correct. This can result, at a micro-level of course, in the servo hunting for correct speed. Since the Mk3 has the highest torque motor ever used in a DD, to the best of my knowledge, this is a potential issue especially for the Mk3. What Richard Krebs devised is a method to further stabilize the stators so as to eliminate that phenomenon so much as is possible. My Mk3 was purchased NOS, and I listened to it for about a year prior to having it Krebs-ed by Bill Thalmann, his agent in the US. I hear a subtle improvement in terms of "smoothness" and therefore "musicality". (You can jump on me for using those vague descriptors, but they fit what I hear.) Before the mod, the Mk3 was already the most accurate TT that I own, but in some ways it was a bit clinical sounding compared to the Kenwood L07D which sits right next to it and feeds the same system. Now I can hardly tell the difference between them except for the fact that the Mk3 is still bang on accurate. I hope I am not putting words into JP Jones' mouth, but he compared speed accuracy between his tweaked Mk3 and his own new SP10R and found in terms of that parameter virtually no difference. Which is why I was able to resist buying a 10R in Tokyo, where you can buy one for under $7K.
