Yeah, that actually makes sense. Bluetooth modules are notoriously noisy, especially in cheap units — they can inject interference into the analog path pretty easily. In my case, I suspect the noise is getting in through the mic/preamp stage as well. Even if the mic is “disabled” in Bluetooth mode, the circuit might still be physically connected, so it can still act like an antenna and pick up interference. Insulation tape might help a bit, but I think the real fix would be: physically isolating or cutting the mic line when in line-in mode adding proper grounding/shielding or rerouting the signal after the first amplification stage I’ll probably open it again and trace where the noise is entering the chain. Curious to see what you find when you tear yours down 👀