Hi Frank,

Some details on the cubes:

There are two magnets on each face with N-S on each face clockwise around block. This allows the blocks to connect any face to any face. Ring lungs are in front of each magnet and provide for the electrical interface, physical contact between blocks, solder lug internal to block. Magnet on bottom provides attachment to ground plane and again ring lung on bottom terminal where required.

Speaker block has 8 ohm speaker and 600 ohm center tapped to 8 ohm transformer. Center tap gives me 300:8 transformer.

NTE equivalent germanium PNP transistors.

Markings done with laser cutter.