Here are the problems with the AKG 5600.

(It looks - judging by the extreme wear on the head-basket - as if it’s been dragged along a concrete floor, held against a knife-grinder, or otherwise mis-treated over and over! ..But that wouldn’t matter if it works properly ..the head can be easily removed and re-sprayed.)

Maybe the electret element has partially lost its charge for some reason - that would explain the increased noise from the internal pre-amp - or continual disconnection and re-connection to and from phantom power (..possibly through the bad connection in the XLR plug..) may have damaged it. However the damage has been caused, the signal is weak, the internal pre-amp noise is too loud, and the hideous buzzing from shorting or disconnection at the XLR makes this mic unusable. It is NOT as described: “A previously used item that exhibits signs of cosmetic wear AND IS FULLY OPERATIONAL AND FUNCTIONS AS INTENDED” isn’t.