I have 10 year old Creative 2.1 audio system that has fairly capable subwoofer, and combined its input with a TPA3110 2x15W stereo amplifier module (for better treble). When both systems are powered together the subwoofer produces a humming sound of around 100Hz(noticeable when no music is playing), and it goes away when later is turned off(while still connected). Creative system (uses TDA8510j IC) uses 11.5V 18.4VA AC adapter, and TPA3110 is given 12V 2A DC adapter. Here is screenshot of audio spectrum app.
How do I get rid of this hum? I confirmed there is no continuity between power supply ground and input ground terminal (of both), thats why I connected them directly in first place. PS: Electronics is not my subject, I do this as hobby.
