Spec Sheet
AT831b Cardioid Condenser
Lavalier Microphone
Broadcast & Production
Features
• Clip-on lavalier mic provides crisp, full-sounding voice pickup
• Also excels as an instrument mic, especially for pickup of acoustic guitar with
included AT8444 instrument adapter
• Excellent gain before feedback and suppression of background noise
• Cardioid polar pattern reduces pickup of sounds from the sides and rear,
improving isolation of desired sound source
• Oers the convenience of battery or phantom power operation
• Rugged design and construction for reliable performance
• UniSteep® filter provides a steep low-frequency attenuation to improve sound
pickup without aecting voice quality
Description
The AT831b is a miniature clip-on/lavalier condenser microphone with a cardioid
polar pattern. It is designed for quality sound reinforcement, professional recording,
television and other demanding sound pickup applications.
The microphone is intended to be worn on the clothing or used as an instrument
mic for excellent yet unobtrusive sound pickup. The wide-range capability of the
microphone ensures clean, accurate reproduction with high intelligibility for speakers
and presenters as well as for instrument pickup. Its small size makes it ideal for use in
applications where minimum visibility is required.
The microphone requires 11V to 52V phantom power or a 1.5V AA battery for
operation. A battery need not be in place for phantom power operation.
The microphone’s cardioid polar pattern provides a 120° angle of acceptance.
The microphone includes a 1.8 m (6') permanently attached miniature cable. Its free
end connects to the provided AT8531 power module via a TA3F-type connector. The
output of the power module is a 3-pin XLRM-type connector.
A 3-position switch in the power module permits choice of o, on/flat response or on/
low-roll-o (via integral 80 Hz high-pass UniSteep® filter). The roll-o position reduces
the pickup of low-frequency ambient noise.
The microphone comes equipped with a power module, a clothing clip, an instrument
adapter, a windscreen, a battery and a protective carrying case.
Operation and Maintenance
The AT831b requires 11V to 52V phantom power or a 1.5V AA battery for operation. A
battery need not be in place for phantom power operation.
To install the battery, remove the cap from the top of the power module. Insert a
fresh 1.5V AA battery (“+” end toward the cap release button), then reassemble the
power module. For longest battery life, the switch should remain o except when the
microphone is in use. Alkaline batteries are recommended for longest life. Remove
the battery during long-term storage.
Output is low impedance (Lo-Z) balanced. The signal appears across Pins 2 and 3;
Pin 1 is ground (shield). Output phase is “Pin 2 hot”—positive acoustic pressure
produces positive voltage at Pin 2.
To avoid phase cancellation and poor sound, all mic cables must be wired
consistently: Pin 1-to-Pin 1, etc.
A 3-position switch in the power module permits choice of o, on/flat response, or
on/low-roll-o (via integral 80 Hz high-pass UniSteep® filter). The roll-o position
reduces the microphone’s sensitivity to popping in close vocal use. It also reduces the
pickup of low-frequency ambient noise (such as trac, air-handling systems, etc.),
room reverberation and mechanically coupled vibrations. To engage the UniSteep®
filter, slide the switch toward the “bent” line. To turn the microphone on without
engaging the UniSteep® filter, slide the switch toward the flat line.
For use as a lavalier, attach the microphone about six inches below the chin.
Anticipate movements that may cause the microphone to rub against or be covered
by clothing, and position the microphone to avoid it.
Avoid leaving the microphone in the open sun or in areas where temperatures exceed
110° F (43° C) for extended periods. Extremely high humidity should also be avoided.
Architect’s and Engineer’s Specifications
The microphone shall be a fixed-charge condenser. It shall have a cardioid polar
pattern with a uniform 120° angle of acceptance and a frequency response of 40 Hz
to 16,000 Hz. The microphone shall operate from an external 11V to 52V DC phantom
power source or, alternatively, from a 1.5V AA/UM3 battery. It shall be capable
of handling sound input levels up to 135 dB (phantom) or 121 dB (battery) with a
dynamic range of 106 dB (phantom) or 92 dB (battery). Nominal open-circuit output
voltage shall be 6.3 mV (phantom) or 5.0 mV (battery) at 1 V, 1 Pascal. Output shall be
low impedance balanced (200 ohms – phantom, 270 ohms – battery).
The microphone shall have a 1.8 m (6') permanently attached miniature cable
terminating in a TA3F-type output connector. The output connector shall connect
to a TB3M-type jack on the included power module. The power module shall house
the battery, and shall contain a switch that permits choice of o, on/flat response
or on/low-roll-o (80 Hz). The output of the power module shall be a 3-pin XLRM-
type connector.
The microphone shall be 25.0 mm (0.98") long and have a diameter of 10.2 mm
(0.40"). Weight shall be 2.8 grams (0.1 oz). The microphone shall include a power
module, a clothing clip, an instrument adapter, a windscreen, a battery and a
protective carrying case. Finish shall be low-reflectance black.
The Audio-Technica AT831b is specified.