LFD AUDIO: Q/A with Dr. Bews. Problem (and solution) re Audio Research driving PA2M

Q: I have an lfd pa2m amp and find there is a hum .any way of stopping this problem?am using audio research ref 2 pre/amp connected by balanced cable but balanced from pre-- then balanced cable connects to single ended cable connecting to lfd amp.thank you

A: Dr Bews replies: I guess it's the balanced to unbalanced cable (pre to power).  The output ground of audio research should be connected to input ground of LFD and the non-inverting output of audio research should be connected to the signal input (center pin of rca) of LFD. This will result in 6db loss in output of audio research pre compared to balanced operation.