Regarding ground connection being connected first and disconnected last IS true if one wire the balanced connections as perhaps intended. The shell which has the 4th terminal on a 3 prong XLR connector is intended for Chassis ground. XLR connectors are available with up to 6 (7) termination points.
Most however don't use this 4th connection point, including me. Pin 1 Chassis Ground, Pin2 Positive Node Pin3 Negative node. So to refer to the OP since your Marantz gear have the same termination on both pre and power amp - your in electrical phase and don't need to do anything else.
As far as balanced operation which in my opinion offer vastly improved performance dynamics for an example and noise rejection and that the interactions of the cable is practically eliminated the list goes on. All the equipment we make is fully balanced form input to output. Even on our economy line Liberty Audio the gear is fully balanced.
Good Listening
Peter
https://pbnaudio.com
Most however don't use this 4th connection point, including me. Pin 1 Chassis Ground, Pin2 Positive Node Pin3 Negative node. So to refer to the OP since your Marantz gear have the same termination on both pre and power amp - your in electrical phase and don't need to do anything else.
As far as balanced operation which in my opinion offer vastly improved performance dynamics for an example and noise rejection and that the interactions of the cable is practically eliminated the list goes on. All the equipment we make is fully balanced form input to output. Even on our economy line Liberty Audio the gear is fully balanced.
Good Listening
Peter
https://pbnaudio.com