I have a pair of headrest DVD players installed and the audio signal from the player to the HU aux-in port is so week that I need to turn the volume way up on both player and HU to have any decent volume. Is there any plug and play device I can add to make the volume higher? DVD player output is RCA (red/white/yellow for audio and video) and HU aux-in port is stereo baby plugs. Where to buy?

tia!