From his days at Santa Clara University to his death, he displayed a deep appreciation for classical music and an aptitude for electronics and engineering.
But for several years, they didn't know what these machines were or how they worked, and it was not until Germany fell to the Allies during 1944-45 that the Americans discovered the new magnetic tape recorders.
He was posted to Paris in the final months of the war, where his unit was assigned to find out everything they could about German radio and electronics.
They found and collected hundreds of low-quality field dictating machines but the major discovery came when Mullin visited Germany just before the end of the war.
He was sent to inspect a site near Frankfurt, where the Germans had reputedly been experimenting with using directed high-energy radio beams as means of disabling the ignition systems of flying aircraft.
"[2] On his way back home to San Francisco, Mullin made a chance stopover at a nearby German radio station at Bad Nauheim, which was already in American hands.
By luck, Mullin's second demonstration was at MGM Studios in Hollywood and in the audience that day was Bing Crosby's technical director, Murdo Mackenzie.
Ampex revolutionized the radio and recording industry with its famous Model 200 tape deck, developed directly from Mullin's modified Magnetophones.