What and where is the power supply for the CD player in a 2007 Kia Optima?

I recently asked a question about trouble with the CD/Radio in a 2007 Kia Optima. I was told to try replacing the "power supply". What and where is the power supply referred to?|||I think you'd get it done from the experts in the local market as power supply is different for different CD players. Also, you'll require special tools to unlock it fully.