You will not create a ground loop if you do proper grounding....
Remember that there is a difference between grounding and earthing. Usually the shield of a cable is connected to the device housing via the connector shells. The device housings should not be connected to any supply or signal ground. This implies that you should NOT use a cable shield for supply or signal ground connections between devices, you should always use separate lines for these.
If your device does not have metal housing connected to earth, you should connect the metal shell of the connectors in your devices at one single point to the supply ground.
Anyhow, in some cases, you have to try out different grounding/earthing schemes for optimizing signal quality.
