Shure A15AS Switchable In-Line Microphone Attenuator

The Shure A15AS is a balanced in-line attenuator designed to lower an audio signal before it reaches a microphone or line-level input. It provides selectable 15 dB, 20 dB, or 25 dB attenuation to help prevent input overload when a source signal is too strong. This compact XLR barrel accessory is intended for professional audio signal management rather than amplification.

It is useful for engineers, performers, content creators, and installers working with high-output microphones or strong line-level sources. In high sound pressure level situations, reducing signal level ahead of a preamp can help preserve usable gain range. The A15AS is also suitable for reducing a mixer output feeding an input with limited headroom.

The A15AS maintains a balanced signal path and has a specified frequency response of 20 Hz to 20 kHz within ±0.5 dB. Its bridging design is intended to minimize loading-related distortion and reduction in clipping level. The result is straightforward level control without changing the fundamental role of the connected microphone or source.

A three-position attenuation switch lets users select the amount of reduction needed for the application. The 15 dB, 20 dB, and 25 dB settings support practical matching between high-output sources and lower-level inputs. It accepts low-impedance microphones, including phantom-powered condenser microphones.

The A15AS installs directly in an XLR signal path, with a female XLR input and male XLR output. It passes phantom power, allowing compatible condenser microphones to remain powered through the attenuator. It can be placed between a microphone and its power supply or between other balanced audio components where moderate attenuation is needed.

Key Features

• Selectable Attenuation: Choose 15 dB, 20 dB, or 25 dB signal reduction.
• Balanced-Line Operation: Supports balanced microphone and line-level signal paths.
• Phantom-Power Pass-Through: Works with compatible phantom-powered condenser microphones.
• Broad Frequency Response: Covers 20 Hz to 20 kHz within ±0.5 dB.
• XLR Connectivity: Female XLR input and male XLR output simplify inline placement.
• Magnetically Shielded Housing: Steel enclosure helps protect the attenuator from magnetic interference.

Design & Installation

The A15AS uses a steel housing with a gray enamel finish and full magnetic shielding. Its cylindrical body measures 19 mm in diameter and 114 mm long, making it suitable for placement in an existing XLR run. The enclosure is designed as a durable inline audio accessory rather than a rackmount or panel-mounted device.

Connect the female XLR side to the microphone or source and the male XLR side to the cable or destination input. Select 15 dB, 20 dB, or 25 dB based on the amount of overload reduction required, then set downstream gain normally. The A15AS is not suitable for condenser microphones using the A-B powering system, and simplex-powered systems should account for its 215-ohm equivalent series resistance.