In the summer of 1945, the company moved from a rental location to their own building in San Carlos, California and a registration request was submitted to name the company "AMP" (which was the founders nickname). Since "Aircraft Marine Products" had already registered this name the solution was to add an "EX" at the end to make it possible for registration. Shortly after the company opened, the San Carlos newspaper wrote an article about Ampex and gave a striking explanation to the origin to the name. "A.M.P." are the initials of the founder, and the "EX" is an abbreviation for the word "excellent," thus indicating the type of product the company intends to make... Alexander Poniatoff liked this explanation.

During the Second World War Ampex was extremely busy meeting U.S. Army and Navy contract schedules and deliveries for the APS/6 and APS/19 radar motors. The war ended and then came cancellation of the military contracts. Poniatoff looked for a new product. The Magentophone was manufactured by AEG (Germany's "General Electric") and Poniatoff was shown a captured German audio tape recorder that had been developed for use by German army journalists.

The first audio tape recorder Ampex Model 200 made its debut April 25, 1948, when the device was used to record the popular Bing Crosby radio show. The recorders sold for $4,000 each. The Model 300 was shipped in July 1949, and design patents of the Model 300 became the NAB standard. By 1950 Ampex pioneered the development of instrumentation recorder with the design and production of a system for the U.S. Navy (Model 500) based upon its audio recorder design. The first prototypes of the FR-200, instrumentation tape transport, were shown at the Eastern Computer Conference in Boston in late 1955. The first rotary head recorder, the VR-1000 was demonstrated in 1956. It made tape recording of TV signals practical for the first time.