Check the listing for details. Tektronix AA 501 Distortion Analyzer Plug in. Condition: For parts or not working. Listed at 1200.00 USD. Up for sale is a used Tektronix AA 501 Distortion Analyzer Plug in.It is being sold AS-IS / For Parts due to its age, it will likely need to be serviced.Original Manufacturer Description:The AA 501 Distortion Analyzer provides completely automatic measurement of level, total harmonic distortion plus noise (THD+N). Automatic set level, automatic tuning, automatic nulling of the fundamental, and autoranging of the display all combine to permit completely hands-off operation once the mode is selected. Just apply the signal of interest and read the 3 1/2-digit display. A novel analog-like bar graph simulates an analog meter to assist in peaking and nulling of applied signals. Sell Smarter with Kyozou.Inventory and Ecommerce Management