Amp fan cooling without dc current in the 110 line


So I just finished renovating an old TV console, modifying it by removing the TV and adding shelves to hold my gear within it. While it has vents on the sides, bottom and back, I’m sure my amp will get super hot inside. So I’d like to put a little fan in the cabinet to cool it off. But I’ve always heard those little computer fans put a lot of dirty DC current in the AC lines, resulting in noise in the amplifiers presentation.
So question is, how to avoid that. 
idahifi
I recently added a cooling fan to my pre-amp from active Thermal Management and it uses a wall wart. I plugged it directly into the wall which powers my system, but since the rest of my system is plugged into AC conditioners, it doesn't seem to adding any unwanted "noise" that I can hear.
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Hu, I've always heard fans put DC current into the electrical system. Maybe that's bunk. Does anyone know for sure
Putting an amp in a cabinet is the wrong way to go because of the heat factor an a fan just blows dirt on the amp.Good luck though.