API

Saul Walker co-founded Automated Processes Inc. in 1968, but the story begins a year earlier when he was commissioned to design a 12-track recording console for Apostolic Studios in New York — the first 12-track studio in the city. That project defined everything that followed. Walker's key invention was the 2520 discrete op-amp: a completely transistor-based amplifier circuit with no integrated circuits, delivering a transient response and punch that no chip-based design could match. API's 500 Series modular format — channel strips that could be swapped in and out of a standard frame — was another Walker innovation, and it became the industry standard architecture that Neve, SSL, and every manufacturer after them adopted.

The 550A equaliser (1968) introduced Proportional Q: the bandwidth of the EQ curve automatically narrows as you push harder. This behaviour feels musical because it mimics what the ear perceives as natural — subtle moves are broad and gentle, dramatic corrections are focused and precise. The 312 microphone preamplifier completed the circuit chain. Together they produced a sound that was characteristically American: forward, punchy, with a particular presence in the upper midrange that made drums feel physically real and electric guitars cut through any arrangement.

API consoles were the first to offer computerised automation, in the early 1970s — predating SSL's Total Recall by nearly a decade. By 1975 the large-format 3224 was installed at A&M Studios in Hollywood, where it captured the sessions of one of the most commercially successful labels of the era. The API legacy extended from Nashville's RCA Studio B to the Hollywood recording complex that produced a generation of American music.

The company passed through several owners after Walker's involvement diminished, but the 2520 op-amp and the 550A EQ remained in continuous production. The Legacy Series, introduced in 1989, brought large-format API console building back to its roots. Over 75 Legacy consoles were built — virtually all remain in daily service, a measure of their construction quality. Walker died in 2014, aged 89.