Hi, I recently completed a class D amplifier PCB design based around the TPA3118D2.
If I power on one the PCBs in my workshop and plug it into a speaker I can visually see noise increase on my oscilloscope, which I have set up and measuring a different circuit which is not electrically connected. I can also hear a practice amplifier I have set up picking up noise that sounds like highpassed radio static. Both these effects stop if I unplug the speaker, mute the outputs using the mute pin, or disconnect power from the PCB.
The amplifiers themselves sound relatively clean when connected to a nearby audio source, but when unconnected they produce a discernible hiss through the connected speaker.
I've attached my KiCad project with the design, as well as screen shots of my schematic and PCB layout. Is there anything you can suggest to help me improve the design and fix this issue? In particular I'm wondering about board layout, design of the input pre-amplifer, and component selection, specifically the ferrite bead and capacitors I'm using for the output filter, which are the following components here:
I am powering the board with a 24V meanwell supply: https://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10001&productId=2219743&langId=-1&catalogId=10001&ddkey=https%3ACookieLogon
Here is my repo with the full Kicad Project: https://github.com/hhaudio/ClassD_Amplifier_Daughter
Here are screenshots of the schematic and layout:
