Sammeli

So, i have 2004 A6 S-Line with bose sound system. I have removed the bose amp and connected speaker wires straight to new HU speaker outputs. The problem is, that when i try to raise volume up, sound starts to cracle and cut out at high frequences. I have figured that it might have something to do with my headunits power supply(?) Thicker power wires could maybe help? Sorry about my bad english. All answers are appreciated!