Every time I do a hacking workshop in Europe students bring in these great old radios from the 1960s and 70s for the "laying of hands"
project (transforming a radio into a Cracklebox.) Some of the best are by Grundig, so I started picking up a few on eBay when I can snag them for less than my $20- limit.
One radio from the early 1970s (I'm not sure exactly which model) arrived pretty damaged, with a non-functional tuning section, but it sounded terrific under damp fingers -- like many European radios of that era, the amplifier section couples to the speaker via a hefty output transformer, just like in a good guitar amp. I stripped off un-needed components, added a few extra touch points and jumper-switches and a transformer-isolated line output for connecting to an external amplifier or PA without fear of electrocution. I re-packaged the whole thing in a magnificent turquoise case left over from another semi-functional eBay find, a Telefunken "Kavalier". This circuit has terrific low frequency content, and sounds great through a wah-wah pedal and guitar amp.
(Scroll down for all three photos.)