On Friday, February 23, 2018 at 3:45:17 PM UTC-5, Terry Schwartz wrote:
On Friday, February 23, 2018 at 9:22:38 AM UTC-6, JBI wrote:
I am using a standard 400 W 12 VDC to 120 VAC inverter to power my
laptop in the car. While this works well, lately I've started doing
audio work with the laptop and feeding the laptop 1/8" audio jack output
into an amp hooked into the car radio. While the laptop is plugged into
the inverter, I get much noise over the audio system. I know the noise
is coming from the inverter, so how would I negate it? I've tried about
5 snap closed ferrite cores around the power cable going into the laptop
but they haven't helped. Thanks.

Get rid of the inverter. They are all horrendous noise sources.

As is the car itself or anything else operating near it.

Run on battery.