I just have to ask…are the jumpers soldered properly? Sometimes people accidentally skip that step, or just solder them wrong.
Another thing i wanted to make sure of…are you able to tap out a rhythm on the tap foot switch? …Just to make sure the microcontroller is working properly.
The faint pulsing you hear is probably just the LFO leaking through to the audio or ground path. It’s normal when the volume is all the way up.
Let me know about the jumpers.