Best wood under audio components?


I am just about finishing my DIY audio rack and wondering about what type of wood would be the best directly under the components? 
I am from Norway and don`t have access to North American maple. Baltic birch plywood is rare also, because we have Norwegian. I would rather have other solid type of wood under my components than plywood, but the efficiency is the major consern, not the outlook.

What type of wood would you recommend?

Thank you! :)
128x128korakotta
You should have included all the info in the first post!
I use a 1 cm thick piece of solid walnut glued on top of the birch ply plinth for one of my 401 turntables. It sounds great. See systems. I use wenge for my armboards on the recommendation of the man who made my slate plinth so you might look at that.
Post removed 
Oops. The man is in Norway. I confused this thread with another one regarding same question.
What do you have in Norway ?
@glow worm,
That is a very interesting way to go. Who woulda thunk it?
I got to try it, as well as using them to cook my steak.
B
I have heard salt blocks such as the Himalayan salt can sweat with changes in temperature and humidity. This can be very corrosive. I would use caution with salt blocks.