Just received my A40's with the MixAmp5.8 today and have a problem. When my rx unit is on it emits a clicking sound through the headset (something like Morse code). It doesn't appear in a regular pattern but does happen all the time. I tried another set of headphones and the problems persists. I turned the tx off and the problem persists. Anyone experience like before? I should mention also that when the rx is plugged in and charging the noise goes away.