Massdrop THX AAA-789

About the Massdrop THX AAA-789

The Massdrop THX AAA-789 is a linear bipolar headphone amplifier developed in collaboration with THX Ltd., featuring their proprietary THX Achromatic Audio Amplifier (AAA) technology and feed-forward error correction. Announced in 2018, it is designed for audiophiles seeking an ultra-clean, transparent amplification with minimal distortion, often described as a 'wire with gain.' It delivers 6 watts per channel into 32 ohms with a record-low total harmonic distortion (THD) of -140 dB at 300 ohms and 100 mW output, making it four times more powerful than comparable amplifiers like the Objective 2, but with far less distortion. The amplifier supports a wide range of headphones, including high-impedance and high-sensitivity models, and features multiple gain levels to optimize listening for headphones or earphones. Its internal design uses Texas Instruments op-amps (OPA 1602A and OPA 564) without any proprietary THX modules, ensuring a transparent and replicable design. The chassis is made from high-grade CNC-milled aluminum with a black bead-blasted finish, measuring 210 x 230 x 57 mm and weighing approximately 1.52 kg. Inputs include stereo XLR and RCA, with outputs for 1/4 inch TRS, 3.5 mm TRS, and 4-pin XLR balanced headphone connections. The amplifier is praised for its ultra-low noise floor, high signal-to-noise ratio (136 dB), and extremely flat frequency response from 20 Hz to 50 kHz. It is not fully balanced internally but maintains a fully differential signal path to preserve signal integrity without added cost. The unit includes an audio signal detector for auto power on/off and offers a smooth, precise volume control. The This amplifier is no longer considered cutting-edge but remains a highly recommended value in the sub- headphone amplifier market.