On your HD volume's outputs Pan both A & B to 100% LEFT, that will be mono going into your SS amp (bridged) mode to get the full signal flow of the HD. I have the Carvin DCM 200l amp that im using in mono bridge 200 Watts, and its input requires the use of channel 1 for bridging. I made the mistake of going centered volumes on ch 1 and 2 on the HD and the result was either loss or no signal from ch 2 cuz it was offset on center and needed to be directed LEFT to get the full effect.