Massdrop x THX AAA 789 Headphone Amp, A Review

Ruben Orduz
4 min readNov 17, 2018
THX AAA 789 + AudioQuest NightOwl

Back in early July Massdrop announced a collaboration work with THX to produce one of their famed AAA 789-class amplifiers for headphones. The technical specs looked fantastic on paper and the THX folks were very active answering questions during the “drop”. Looking to upgrade my solid state amp (I already have a wonderful tube amp), I decided to join the drop. The bad of all of this was that the unit wasn’t schedule to ship until Feb 15th, 2019! As luck would have it, their production went way ahead of schedule and couple of weeks ago I received notice from Massdrop that the amp was about to ship. I received the unit early this week and began the burn-in process. After almost 50 hours of burn-in I had a few hours of critical listening. Below are my thoughts:

Unboxing: Massdrop and THX went with sensible, no-nonsense packaging. Nicely padded box, easy access to the amp, power adapter, and accessories. Super utilitarian, no frills.

Aesthetics: Minimal and functional. All back anodized metal. 4 unobtrusive nobs (from left to right: power, gain setting, volume and input selector) and 3 understated jacks (left to right: 4-pin XLR balanced, single-ended 1/4'’, single-ended 1/8'’). All well marked and easy to navigate. All in the right place, no gaudy colors or logos.

Build Quality: it’s a good build, but not great. There’s some vacillation with the power and input select switches. It’s minor, to be sure, but for a unit costing north of $300, I expect excellent build quality and care for details. Aside from that everything else seemed in place and securely so.

Specs: way too many to list. For complete list click here. But here are some worth highlighting:

Output power: 3000 mW, 16 ohms, <1% THD (watts per channel)

Output power: 1800 mW, 32 ohms, <1% THD (watts per channel)

Output power: 200 mW, 300 ohms, <1% THD (watts per channel)

Output power: 100 mW, 600 ohms, <1% THD (watts per channel)

THD: -143 dB, 300 ohms, 1 mW: 0.000007%

THD: -135 dB, 300 ohms, 100 mW: 0.000018%

THD: -135 dB, 32 ohms, 1 mW: 0.000018%

THD: -133 dB, 32 ohms, 100 mW: 0.000022%

Ruben Orduz

Software, hi-fi audio, data, and all things AI/ML.