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Audio-Technica ATM31a

Cardioid Condenser Microphone

The ATM31a is a cardioid condenser mic with an electret capsule. It was presented as an all-purpose studio or field microphone, and could be powered via phantom power or an AA/UM3 battery.

Note that the specs change if you run the mic from a battery rather than phantom power. Using a battery:

• Impedance changes from 200 ohms to 270 ohms
• Dynamic range drops from 113 dB to 99 dB
• Sensitivity changes from -44dB (6.3 mV) to -45dB (5.6 mV)

The ATM31a is a revision to the original ATM31 (circa 1981). The newer model has a wider frequency response, higher sensitivity, and can be used with phantom power (meaning, the battery is not required). The published polar and frequency-response graphs are different, but Audio-Technica has not described the changes made to the mic’s components.

The Audio-Technica ATM31a is also known as: ATM31, ATM-31, ATM-31a.

The mic was released in 1981.

Specifications

Frequency Response - CardioidClick Graph to Compare!

Pickup Patterns	Pads & Filters
Cardioid (6.3 mV/Pa; 30 - 20,000 Hz)

Capsule Dimensions	Impedance	SPL/Noise
Diameter n/a	200 Ohms (Low)	Max SPL: 137 dB Self-noise: 14.0 dB(A)

Weight	Length	Max Diameter	Interface(s)
200g (7.05oz)	193mm (7.60'')	50mm (1.97'')	3-pin XLR male (1)

Power Specifications
Requires phantom power Has battery compartment (1.5V AA/UM3) Phantom voltage: 9-52V DCv

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