Why is my music faint with loud static?

I’ve had my iPod classic when I was younger, but at a certain point the music would be very faint and there would be loud static. This would happen when I would have headphones on. So I stopped using it back in 2010ish.

So today I’ve pulled the corpse from the grave to see if I can fix it. I had to change the battery since it was swollen, and I’ve changed the audio-jack and hold button component.

I have tested the audio-jack and it still does the same thing, faint music with loud static. Imagine a terrible car stereo with the bass too loud and the actual music barely audible.

I’ve also tried docking it in my car and it sounds great as it should.

I’m not sure what can be wrong with it. I would appreciate any advice. Thank you!