Hmm, this gives me an idea - if we came out with a time machine kit you guys could build it first, then order an amp kit, and then jump forward 4 weeks.
Ooh, and if you make a mistake in the build you could just go back before you did and correct the mistake before it happens (happened?).
I can't really think of many other practical uses for a time machine, but this might make it all worth it. I googled, and it has been done before with vacuum tubes...
(http://vignette2.wikia.nocookie.net/bttf/images/0/04/TimeControlTubesModel.jpg/revision/latest?cb=20080802225029)