This LM380-based circuit was found in documentation from the 1980s. The components are current, and the transistor may be a general-purpose equivalent. Note the use of a medium impedance speaker.
I found this circuit in a Popular Electronics from November 1999. The magazine is no longer...
This circuit of a 1991 PE Hobbyst Handbook allows the brightness of the incandescent lamp to be...
This simple operational amplifier tester was published in the November 1987 issue of Radio...