Aluminum in cld plinth

It might be worth a try. How do you plan on implementing it into your design? All aluminium or sandwich together with another material?

I am hardly an expert, actually very far from it.
Some TT designs use aluminium as a plinth material.
However sandwich is kind of new to me and might or might not be beneficial. It is hard to tell, at least from my point of view. I am working right now on the plinth for my Lenco. Materials used are premium MDF 3/4 inch and Baltic Plywood which is better then Birch in my opinion (13 layers in 1 sheet ). This plinth is my second one, so my experience is very limited. My first one is made from Bamboo BB, walnut for arm board and Mahogany motor stand.
I also didn't find a lot of support but took a chance and it worked just great. Bamboo BB is about 10 times harder then maple BB and it sounds GOOD (I don't want to put to much sugar in your tea - but it sounds GREAT ). What I'm trying to say try it - my advice, make it heavy (40-60 pounds ). You can also incorporate a dedicated TT stand & platform for even better performance.
I would only recommend that you use top & bottom layers out of Ply. or MDF + separate arm board(s).
Keep us informed on the progress and your final design.
Good luck on your project.
Mariusz

I don't know the details of your design or what TT it is based on. But I would used Ply. or MDF for top & bottom from practical point of view, could be easier to work with on finale details and mounting hardware and such. It may also be a little safer approach ( using aluminium/MDF/Ply. together for the first time ). MDF is a good material for the arm board so is Ply or solid wood. I simply don't have enough knowledge or experience to predict the effect of the 1/8inch aluminium sheet on the arm/cart. I would just play safe for now and if it worked in this project you can always try it next time (top, bottom - Alum.).

Personally, I like hardwood for top - It is not a sound quality decision rather aesthetic. Wood also has a good acoustic, isolation and dampening properties. Arm-board...well, most guys recommend MDF for its properties. However to much MDF can cause sound to be "to dark/lifeless". But I guess it is the best way to go (safe).You could also try to make a 2 layer arm-board - MDF&Ply or wood. I like to experiment with different wood species. I love the warmth of wood and it may have something to do with my passion for woodworking.
I kind of know what you are thinking. But don't worry. It is normal when plans change. It happened to me more then ones. It is all for the better. Think positive - and whatever you are going to build will most likely be better then the shelf units at your average audio shop.

Mariusz