General Description

The Shure Model A15RF In-Line RF Attenuator provides all types of balanced audio systems with greatly improved immunity to radio frequency interference (RFI). It is especially useful in applications where balanced audio devices near strong RFI sources, such as AM radio stations, are connected by long cable runs.

The A15RF will not degrade system sound quality or alter system frequency response. In cases where interference is present but not audible, the A15RF can improve perceived sound quality by removing low level interference components from the audio signal path. It passes phantom power and is transparent to differential audio signals ranging from DC to 2 GHz.

The A15RF is a passive device and will not damage other equipment. It does not present any additional load to the signal sources, and can be used with phantom-powered mic-level or line-level devices.


For best results, connect an A15RF between the cable and the affected device. If interference remains audible, install the A15RF at the other end of the cable, or place one A15RF at each end of the cable. In extremely severe cases, connect two or more A15R attenuators in series. If the problem persists, replace the cable and check for faulty or unbalanced connections.



Common Mode Attenuation 50 Ω In/Out
Differential Mode Attenuation 50 Ω In/Out

Maximum Operating DC Current Rating

20 mA maximum


0.4 Ω

Operating Temperature Range

-40° to +85° C (-40° to 185° F)


Full magnetic shield; steel with black chrome plating


19  mm(.75 in.) diameter; 69.85  mm (2.75 in.) long

RFI Attenuation

Common Mode Attenuation

Differential Mode Attenuation