Hi Eric, Is the sampling clock for the internal sound card driven by the reference oscillator? Or does it have an independent crystal oscillator for sampling? Thanks and 73, tom w7sua On 5/22/2019 10:19 AM, Eric Swartz - WA6HHQ, Elecraft wrote: > The K4 also has one USB-B on the rear (with internal sound card and > mutiple comm ports like the K3S).