Noise with TPA3110D2 amplifier on the same power supply as an USB HUB
There are many possibililties. You may benefit from 1 ohm resistor between the 12v and your amplifier, followed by the big cap aross the amplifier VVD/GND.

The switch_reg spike voltage may be so big the amplifier input transistors are driven into overload, thus acting as a mixer/down_Converter.

Also, switch_regs have input_output coupling capacitors, for EMI filtering reasons and safety reasons. These capacitors ENSURE trash is coupled onto the power lines, and that trash energy WILL find a return path, using ALL possible paths including thru the input wiring of your signal to the amplifier.