How to remove the tube cage SFS-80

I recently acquired a Sonic Frontiers SFS-80 with everything except the instruction on how to remove the tube cage. The manual says it is "quite difficult to remove" (on purpose) and suggests I look at the "insert". which I do not have.

Thank you for your help.
Its much simpler that you might think. There a banana type plugs on the four corners of the cage which connect to clips in the top of the amp - they only appear to be tightly gripped. Actually they are not, its just that it takes a bit of initial force to release the clip. All I do is simply put my hands on both sides of the top of the cage and pull up/forward until the clips release on that side, then I put my hands on the underside of the cage on both sides (there will no be a gap starting at the transformers and working forward) and lift up. Once the case is removed, I replace it lightly on the clips so it doesn't reseat itself. Don't worry, you wont hurt any thing in removing the cage. If you don't understand my method, you can always insert a broad, flat, plastic tool (like a spatula or "pancake flopper" between the amp surface and the cage and pry up. Probably easier that way 'til you get used to doing it.