Shielded

Where Do You Use Shielded Audio Cables?

You use shielded cables to protect sensitive electronic signals from interference caused by electrical mains, heavy electrical equipment, and cellular and radio equipment signals. Common applications include:

Sound and Audio Systems

Protect your sound system or stereo from picking up the 60-hertz hum generated by mains, transformers, motors, and appliances. This is particularly important for low voltage audio signals from sensitive equipment like headphones, microphones and turntable pickups. Also, they keep the mains hum from your low-frequency subwoofer speaker cables.

Intercom and PA Systems

Intercom and PA cables may need to run long distances close to mains cables so it's best to use shielded audio cables to minimize electromagnetic interference (EMI) from mains cables and equipment.

Commercial Use

You can use suitably rated shielded audio cables in commercial buildings for communications, notification, and control circuits. You can also use shielded audio cables for fire alarm circuits provided they have a firepower limited plenum (FPLP) cable rating and a red jacket.

Construction of Shielded Audio Cable

A shielded audio cable has two solid or stranded copper wire cores with polyvinyl chloride (PVC) colored insulation and a foil shield under a PVC jacket. There's a bare drain wire under the jacket in contact with the aluminum foil shield.

Purpose of a Balanced Audio Cable

Two wires running side by side feeding an audio signal both pick up interference from EMI sources. The polarity of the induced signal will be opposite in each wire, so if the wires are the same length and follow the same route, in theory, the interfering signals will cancel each other out, especially compared to a coaxial cable where the shield acts as a return wire.

This natural noise cancelation effect is increased if the cable has twisted pairs. In practice, some noise still gets through due to manufacturing imperfections, hence the need for a shield.

What is Electromagnetic and Radio Frequency Interference

Audio wires are subject to two types of interference. Electromagnetic interference (EMI) is low frequency 60 Hertz interference from mains equipment that primarily affects analog audio signals. Radio frequency interference (RFI) is high-frequency interference from wireless, radio, and cellular signals. Although not audible, it can interfere with digital audio signals.

AWC shielded audio cable uses an adhesive aluminum foil screen that's wound around the cable during manufacture together with a drain wire. This form of screening provides excellent protection against EMI and RFI.

Shielded Audio Cable Specifications

AWC Shielded Audio Cable Specifications:

AWC Shielded Audio Cable Approvals:

• 24 to 16 AWG Shielded Audio Cable:
  • National Electrical Code (NEC) CMR FPLR (communications riser cable, FPLP)
  • California Energy Commission: CMG FT4 (communications general-purpose, FT4 Vertical flame test)
• 14 to 12 AWG Shielded Audio Cable:
  • NEC CL3R (Class 3 riser cable)
• Voltage rating: 300V
• Temperature rating: 75° Celsius