I remember getting a Lafayette 3-pickup electric guitar and building a Heathkit guitar amplifier. That thing had a dual-spring reverb too. I got a 4x12" speaker cabinet with Celstion speakers from the newspaper classifieds for $75. That thing was loud, and had a super high-frequency squeal when you turned it up. I think they just used a high-bandwidth amp design from their scopes rather than design a ground-up audio amp. But it taught me about oscillations, shocks from ungrounded chassis voltages, and electronics in general.