I have got a CVP-301 in service right now which I think ihas the exact, or very close to the same fault.
I would like you to run some teste for me:
Turn off the unit - on the keyboard push down [C#2], [F2] and [G#2] keys and whilst holding down the keys turn power on. Keep the keys depressed until you get to the TEST screen.
Using the [TEMPO+] button go forward to TEST 15 ([TEMPO-] goes backwards).
Use the [START/STOP] button to start/stop each test.
I want you to run TEST 15, 16, 17, 18, 19 and 20.
On each test - listen carefully if you can hear that crackle whilst the test is running and also take note if the crackle is in one speaker or both speakers (ie left and/or right).
You can just turn power off/on when done.