Ps audio Class D amp sounds like a wah-wah pedal after warm up.

PS audio HCA-2 with full blown Reference Audio Mods was put up after it started this long ago but wanted to maybe get it up and running or transfer the parts to a stock one they can be had for cheap. Has anyone ever experienced this strange sound in a class D amp. I have heard hiss, hums, tube rush but never wah wah wah, kind of like a guitar wah wah pedal, and it gets louder and needs to be shut down quick. One of the mods was to add about 16 power supply caps. Since it takes 15-30 minutes before it does this I'm guessing power supply caps, bad solder joint in power supply. I know nothing about class D always owned tube or transistor solid state,or is this a trait of something else in class D type circuit, or board, thanks for any insight or help.