From the earliest days, founder Saul Walker's designs for API consoles were based on modular units (preamps, equalizers, etc.) in its 500-series that could be interchanged to create a customized mixer at an affordable price — without sacrificing quality. And over the years, users on non-API consoles who wanted that sound had to create customized interfaces to use the modules in studios without an API desk. In 1985, API owner Paul Wolff debuted the API Lunchbox — a convenient housing for up to four API modules in a lunchbox-sized chassis. Easy to use and portable, this led to larger versions (up to 10 slots) from API and other manufacturers. Eventually, other companies adopted the modular 500-series, leading to an entire industry of products in the 500-series format.