My Hobbit Black arrow has a ground loop isolator installed by the factory and it also has hiss and pop on startup. I think what's needed is a simple stereo relay like what's typically used on car stereo setups with power on thump. Like one of these two?
https://www.amazon.com/NOYITO-Loudspeaker-Protection-Amplifier-DC12V-24V/dp/B07BJHKMGZ/ref=sr_1_2
https://www.amazon.com/gp/product/B00CRYUSR2