PC accessories maker Razer buys SF theater audio firm THX Film fans know the distinctive THX “deep note” audio trademark that precedes blockbusters in theaters and home videos. Razer, the Irvine maker of gaming keyboards, mice and other PC accessories, on Monday announced it has bought THX Ltd., which originated in 1983 when “Star Wars” creator George Lucas wanted to ensure better audio in theaters for his films. In an interview, Ty Ahmad-Taylor, who took over as CEO last November, said THX didn’t need the deal to survive, but said the sale will help his company expand its workforce and market. THX’s technology certifies that an audio and video system meet a certain quality standard for playback. Singer Beyoncé’s Formation World concert tour appearances, for example, started with a THX deep note blasting the audience.