platter mats for dd turntable?

It's worth bearing in mind that the Technics 1200's platter has a slightly raised lip all the way around the edge. Some companies are starting to notice and provide slightly smaller mats that fit inside this lip. I've had best results with a SoundDeadSteel Isoplatmat (285mm to fit the 1200) directly on the platter to damp any ringing and a Funk Acromat on top to interface with the record. This combination only lowered the noise floor a touch, but it did things with air and space that I hadn't heard from a Technics before.

I wouldn't worry too much about matching the original mat's thickness - the Technics' VTA adjuster is very flexible and has quite a wide range.

Info from Kevin at KAB about the diameter of mats for the 1200.

" I am seeing lots of discussion on platter mats and I wanted to clarify some things. First some observations on the '1200 platter and the raised outer edge. The outer edge is raised only slightly, about 0.008 inch. The purpose of this is to ensure that the rubber mat puts some pressure on the outside edge. If you take the platter off, hold it in by the magnet below and strike it, it will ring. The only way to stop the ringing effectively is to grab the outside edge, touching anywhere inside that perimiter, is not effective. I have never suggested that mats should fit inside this edge, on the contrary, mats should fit over and onto this edge. So far the best system I have seen is the SDS Isoplat Mat 295mm and the thin tecnnics stock mat. these 2 give good overall mat height and stop all ringing. Do not use mats that are under cut, and always remember that you need a fair amount of weight as well to control the resonance in this platter."

Sorry, but I'm afraid I don't buy that.

Firstly, the outer edge may only be raised 0.008 inch, but vinyl reproduction is all about precision. Compare that to the width of the groove that the needle is trying to trace and it suddenly doesn't seem so negligible.

Secondly, with my 285mm Isoplatmat (NOT touching the raised edge, remember) and Acromat on, I get a satisfyingly dull 'thunk' when I flick the edge of the platter. The ringing is completely damped without anything touching that rim at all. As an added bonus, I know my records are sitting on a perfectly flat surface with no possibility of dishing in the middle.