Claud,
I had a similar problem recently and appreciate the frustration. Sent my Proceed AVP into Madrigal (for the 3rd time) to fix a DAC problem and light problem. When it came back I had a very disturbing hiss. Had already fixed ground loop from cable TV problem months ago. I didn't want to send AVP back to Madrigal since they take forever, so I spoke with the Proceed tech and had them send a new DAC board since that was the major change. Turns out Madrigal FORGOT to put a screw into the inner board that grounds the AVP!! As soon as a screw was put in the hiss was gone. I have never heard of this happening to anyone else. After spending 3 weeks trying to figure out what it was, I never would have found it without taking the thing apart. Hope this helps.
JJ
I had a similar problem recently and appreciate the frustration. Sent my Proceed AVP into Madrigal (for the 3rd time) to fix a DAC problem and light problem. When it came back I had a very disturbing hiss. Had already fixed ground loop from cable TV problem months ago. I didn't want to send AVP back to Madrigal since they take forever, so I spoke with the Proceed tech and had them send a new DAC board since that was the major change. Turns out Madrigal FORGOT to put a screw into the inner board that grounds the AVP!! As soon as a screw was put in the hiss was gone. I have never heard of this happening to anyone else. After spending 3 weeks trying to figure out what it was, I never would have found it without taking the thing apart. Hope this helps.
JJ