Jsman-
*Mine is 16"W x 3.75"H x 9"D
*Definitely a sonic improvement with my VPI Aries2 ext. w/ 12.5 arm. Immediately apparent with the first record played.
*I suppose you can keep it running All The Time, but I doubt there's a sonic reason to do so, and one advantage to using the SDS as the motor on/off switch is that the SDS can also be used as a reference to how much time is on your cart-as long as you're consistent about turning it off after every listening session.