Hiss is a characteristic of tubes. Try different ones. Some will hiss less, but they all do it. It is mostly an annoying academic problem because music at any reasonable level will mask the hiss.
Hum is a grounding and shielding issue. Experimaent with different ground configurations. Unfortunately some of the grounding configuration is in the equipment circuitry. Hopefully the designer got this part right.
Hum is a grounding and shielding issue. Experimaent with different ground configurations. Unfortunately some of the grounding configuration is in the equipment circuitry. Hopefully the designer got this part right.