No ‘scope? This simple circuit can help you quickly see if you have any oscillation problems on your opamp or amplifer circuit. Note, its NOT designed to be connected to high impedance nodes. Oscillation Sniffer by Bonsai
This set of articles was written in the early 1980’s by Bob Cordell, a few years after Matti Otala (RIP) identified TIM (Transient Inter-Modulation) as the probable cause of sonic imperfections in high feedback solid state amplifiers in the 1970’s….