If you have the manual or packaging, write down where to find replacement tubes and which specific type to look for. A manual might just say to buy from Mcintosh, but there are other options.

With lumber, you can have stronger joints, like mortice and tenon. Plywood joints are really limited to rabbets and you need more pieces to stabilize the corners. It is difficult to find new plywood with a thick outer veneer, so a deep gouge will go right to the inner core layers. A gouge in lumber looks less obvious, unless the wood is stained a strong color. Lumber will give you the option for a nicer looking bed frame and if well built will outlast a plywood bed frame.

istim 805 Recently got this and it will run a lot of electrical patterns (constant, sine wave, rapid on-off, etc) which can be tweaked. It’s about the size of an old cassette Walkman. It’s strong enough to be too much, but the intensity is variable.