Pl511

Could be some audio settings. Check through the options for anything weird. Sample rate, buffer size, things like that. Make sure it's routed to the correct output, some a virtual output that can't handle it.

Also, start with a regular preset, those should be normal-sounding enough to not have some bizarre compression or other problems.

The only problem I've ever had with P4 was that the polyphony, which was at 1 by default, no idea why. Almost had me sending a mail over to their site before I caught it. No idea what could distort it. If nothing else work, turn down its volume.