Lew, I was notified that you had asked about a DP80 in this thread. As you may know, I fully restored a DP80 awhile back. From a purely listener's standpoint, the DP80 "sounds" every bit as good as any of the Lencos I've built - and better than some. In fact, it with a Kuzma Stogi Reference and Sumiko Celebration is one of five tables I own and one that I turn to as often than not (Not Mentor, 2 Lencos, and a Garrard 301 being the other three). Of course, this could owe to plinth materiasl, arm/cart combos, etc., etc., etc. I cannot tell you the technical reasons for speed adjustment of the DP80 like I could the Lenco, but I do know what I hear. For what it's worth, and all that. :)
If you'd like more detail than this forum will allow, please e-mail me. I post here such that others having your same general question may have intertest salved or, better yet, piqued!