As I was looking at bluetooth class D amps...and wondering how anyone could could make such wattage claims for small boards, it occurred to me: fix the amp you have...the one that weighs 35 pounds. So....I'm rebuilding my Grandfather's Scott R75s. I've had it for years and knew it needed attention. I used it for a long time about a decade ago. The sound was pretty muddy. Not much high range at all. I had no idea about electrolytics going bad. So, I hope I didn't cook anything in those years. I'll start with the caps and see what results. I suppose I should add that my first system was a Heathkit SA-3 mono tube amp--from the same grandfather. Which I now wish I had kept. Thanks for all of the info I've read, and for the responses to my few queries.