same here ….
although with my hm-700
by the way i had the same problem with my hd-201.
first i thought it was a mic/line-issue.
the i thought it had to do with a firewire connection.
but now it seems it has to do with the intern audio circuit.
i discovered that the sound (a mix of hiss and high frequency beep) is related with the xlr-inputs. if you change one of the inputs it seems that the sound on the other channel gets stronger or weaker.
i wonder if it has to to with phantom power 48+ volts
hope someone knows more about this issue.
best regards,
ralph, the netherlands