On August 18, 1957, the station switched to an all jazz format, becoming the world's first all-jazz station. It was branded "The Jazz Knob". Its owner was Sleepy Stein, who was able to get permission from the Federal Communications Commission for a power increase by switching the frequency to 97.9 in 1958. It broadcast from a studio at their transmitter site atop Signal Hill, near Long Beach Airport. The building and tower remain to this day, though the station has moved away to Flint Peak near Glendale. The station's original high-power transmitter was a Western Electric 10 kW that had previously been installed at KNX-FM.