"It doesn't sound right" is where good troubleshooting goes to die. The more precisely you can describe a symptom, the less everyone has to guess — including you.
Hum is continuous, sits under the music, and usually ignores the volume knob. That points toward power or ground.
Hiss is a smooth rush, changes with volume, and is usually a gain stage doing what gain stages do.
Buzz is harsher and often has a source — a dimmer, a fridge, the TV, a charger. Interference has sources, and sources can be found.
Crackle that moves when you touch a knob is a dirty control. Crackle that moves when you wiggle a cable is a cable.
Then the splits: one channel or both? Speakers or headphones? Does it follow the source when you swap inputs? Each answer cuts the problem in half.
The discipline fits in four questions: when does it happen, what makes it better, what makes it worse, what changed last. Write the answers down before you post.
Try it now — describe your current (or most memorable) fault in three sentences using those four questions. If the exercise makes the cause obvious before anyone replies, that is the point.