Seventy years ago this month, the May 1956 issue of Popular Electronics carried this ad for the Allied Knight Kit Space Spanner receiver.  The three-tube AC-DC set covered the broadcast band and 6-17 MHz shortwave.  It included a 35W4 rectifier and 50C5 final audio amplifier.  The heart of the set was a 12AT7 which served as regenerative detector and first stage audio amplifier.