When using the RTA for distortion analysis I find that the distortion components are not correctly Identified with some sources. If I use a battery powered wien bridge osc the identified harmonics are correct. If I use my dac (Cambridge audio magic) they are not) I can use a cursor and identify the correct value. but it reduces the efficiency of the tool. Has someone else observed this behavior. Is there a simple fix. It almost seems like a frequency discrimination problem although I am not sure how that would work