Entrance Cable line causes hum in Home Theater Audio

Hello @m6bigdog, thank you for taking the time to reach out on social media.

If you're experiencing a hum in your home theater audio system and suspect it's related to the entrance cable, it's important to address both the potential grounding issues and the AC voltage problem.

Regarding your question about the acceptable AC voltage on an ungrounded entrance cable:

1. Typical AC Voltage: For residential power, the standard AC voltage in most places is around 120 volts in North America or 230 volts in many other parts of the world. The actual voltage can vary slightly (typically within 10% of the nominal value).

2. Ungrounded Cable Concerns: An ungrounded cable should still carry the expected voltage, but it poses safety risks and can lead to electrical noise and interference. The hum in your audio system is often due to grounding issues or electromagnetic interference, which might be exacerbated by an ungrounded cable.

3. Safety and Measurement: To measure the voltage, use a multimeter to check the voltage between the live (hot) and neutral wires. In a properly grounded system, you should see a voltage close to the standard value. If you're measuring between the live wire and ground and seeing unexpected voltage or significant differences, it could indicate a problem.

4. Fixing the Hum: To address the hum, consider:

   • Ensuring Proper Grounding: Make sure your audio equipment and electrical outlets are properly grounded.
   • Checking for Ground Loops: Hum can result from ground loops. Use isolation transformers or ground loop isolators if needed.
   • Inspecting the Cables: Ensure all cables are properly shielded and connected securely.

If you are unsure about electrical measurements or grounding issues, it’s a good idea to consult a qualified electrician to ensure your home’s wiring is safe and compliant with local electrical codes.