Static when using aux with 12v adapter

[Ojurb]

Hi everyone, im having a bit of an issue with static when I use the 12v plug and the aux input in my yaris, if I run the phone off the battery its perfect, but if I plug it into the adapter the volume drops and creates static, I have the stock stereo, I did perform the toyota aux fix where I soldered the 2 pins together so it would switch to the aux input, any way to fix this? Thank you.