Vintage DD turntables. Are we living dangerously?

Pryso, No, the Krebs mod has to do with motor and PS. You are free to choose your own mat. Richard is around here somewhere; perhaps he can weigh in on the mat question.

Fleib, I really have to say that I am so content with the L07D "as is", that I don't worry about ring vs no ring or how heavy is the record clamp. I am either getting old or lazy or both. However, I have all the doodads here, should I be moved to try the ring and heavy center weight again. I should think that a vacuum mat where the surface is metallic would be a very tricky proposition, since it would be difficult, maybe impossible, to achieve a good seal between vinyl and metal. Thus there would be a constant low grade "leak" of air and possibly not only no vacuum effect but noise added as well.

SP10 Mk3 a la Krebs is getting better from the very good baseline.

Pryso
My upgrade concentrates on making the motor and speed sensor do what the designer intended them to do. As designed and as built are two entirely different things. All the Kings horses cannot put back together what is broken in the drive. The technique is applicable to any DD. The TT-101 would be a good candidate

Re mats. In earlier TTs that I built, I experiemnted with rubber, lead, chamois and acrylic. I gravitated towards acrylic. Then more than 20 years ago I purchased my SP10 MK3.
Didn't like the original rubber mat and couldn't use the chamois because of the platter lip. I found that the acrylic worked quite well. I didn't think of trying copper or SS.
But I felt that the platter itself was compromising things so I made a new one in a tri-laminate of acrylic, duralium and lead epoxy'd together.
This I liked a lot and is what I still use today with a SME reflex clamp.
Pictures available on my Krebs upgrade web site. The black triangular unit.
All that said, I have heard exceptional performance from MK3's with original platter and both SS and soft mats. These were both take no prisoner systems in the USA that are simply spectacular.
So today I would think twice about discarding the original platter and spend more time on the record / platter interface.
There are so many options and ultimately it seems to come down to personal preference.

Lew, that is what I remembered but wanted to be sure.

Richard, thanks for adding your comments.

I have had a few weeks now to assess the effects of the Krebs mods on my SP10 Mk3. I was kind of a reluctant dragon going into this endeavor, because I was very happy with the Mk3 "as is" (now "as was"). When listening to the Mk3, I did not really perceive the kind of issues or colorations that were supposed to be "fixed" by the Krebs approach. This is in contrast to my experience with the SP10 Mk2, now departed. I could easily hear the "gray"-ish coloration that Richard perceives to be caused by an over-active servo (for want of a better way to describe it), when listening to my Mk2. In any case, you have to hear a modified Mk3 in order to know what you were missing. Richard's work makes the Mk3 more open and musical sounding, more of what HP used to call "continuousness". Based on this experience, I would suggest that the Krebs mod is also a no-brainer for the much more common Mk2. The cost is modest (especially for the Mk2 mod) compared to the benefits. Thanks, Richard.

I encouraged Richard to consider developing a modestly priced modification for the SL1200 servo and motor, since there are thousands of them in every day use. Apparently, he is already at work on that.

Henry convinced me going for a 101. my unit will arrive in about 2 weeks and I hope it has not too many defects as it is "for repair". I got a lot of information from Henry (👍 many thanks) also preparing my service team which is ready to start 🔧. now I am collecting ideas what kind of armpods I should use? Henry's pods look very nice and stable. I 'd like bringing in at least four arms on the DD, also an EA-10 which has a huge counter weight below of the arm. Therefore I need space below of the armboard.