MFH’s Stella Amplifier kit
My husband has designed an amplifier, and is selling it as a kit: The Stella Amp. It sounds great; I’ve heard him put a lot of music through it, from iPod to guitar to harmonica, and get an astonishingly diverse range of awesome sounds out of it.
He has high-quality design documentation and step-by-step assembly instructions available through the link above. I’ve seen other electronics kits that leave the novice guessing; this is not one of them. There is plenty to learn with this kit, and my husband is an able teacher.