Noticeable Hissing or Electrical Noise When Using the RCA Input?

Possible Causes:
- The RCA cable has inadequate shielding.
- The source device has a grounding issue.
- The volume is set too high.

Solutions:
1. Try using a well-shielded RCA cable.
2. Check the grounding of the source device. If necessary, try a suitable audio isolation transformer.
3. Lower the volume to a moderate level (below level 10) and check whether the noise decreases.