Review: Drop THX AAA 789 – Chica Style!


This review is not by any of the HFN Staff members but it is a guest article written by Hifi Chica. I’ve always wanted to have a female writer for but female audiophiles who like to write seem hard to find. When she asked me if I was interested in publishing a guest review, I did not hesitate. It’s important to know this is a guest review, so it doesn’t look like our regular reviews, neither does it contain all the info we usually cover. But this is a point of view of a lady and of how she sees and feels audiophile gear. Let’s discover that together in this article. Let us know in the comments section what you think of her first article and if you want to see more of her reviews.

Disclaimer: The Drop THX AAA 789 was bought Hifi Chica herself  directly from for around $400USD at that time. 

 About THX Ltd

About two years ago, I read about a freakishly praised headphone amplifier from no other than THX. THX, Lucasfilm THX, I was wondering? Well yeah. But while back in the day THX was more about movie theatre quality certifications (among other things), they’ve also ventured to making products themselves, but not in the traditional way. They’ve engineered a THX Achromatic Audio Amplifier (THX AAA™); basically an amplifier module that performs great, and they are selling this amplification module to other manufacturers.



Drop (ex Massdrop) THX AAA 789

The headphone amplifier reviewed here is the first commercial product utilizing the THX AAA technology. By now, there are already many others (by Benchmark, Monoprice, Fiio and SMSL). I won’t go into details about Drop, but the collaboration was a success as Drop wanted to create their own high end headphone audio products and THX was new and available. The timing was great – this amplifier was sold out for about a year – and after market prices are soaring. Now that other manufacturers are utilizing the same technology in their products that compete in the same price class, I would think that this amp’s crazy demand will die off. Nevertheless, that does not make the amplifier any worse; on the contrary, it is a great headphone amplifier, but not perfect by any means.


The packaging of the 789 matches its’ looks: clean and simple. You receive the amplifier wrapped in a black silkish looking cloth bag that says Massdrop (probably Drop today), and next to that a switching power supply that can handle 100–240 VAC (US plug; adapter needed for global use). The device has a 1- year manufacturer’s warranty.



Features, Looks & Build Quality

On the back, the 789 has left and right single ended input, single ended pass through and balanced input. This amp is not a pre-amplifier, so when using the single ended pass connectors, the volume pot of the unit won’t affect the volume level. On the front side, this amplifier’s layout is minimal. There’s the power switch, balanced output, quarter inch single ended output, 3,5mm single ended output, a gain switch with three levels, the volume pot and an input switch to choose between the an output or pass option. There’s also a tiny light that indicates whether the amplifier is on or not. It changes to red if there’s a problem or when the amplifier is not ready to function.

I think this amplifier is fairly big for a desktop device, but I understand it’s not easy to pack 6 watts of headphone amplification in a cute slim box. The 789’s looks are very minimal, which fits nicely with its matte black finish. On the other hand, it almost looks like a car stereo from the beginning of the 80s. But they’ve done pretty good considering it’s a “budget high end” device. The light indicator looks cool, since the hole drilled for the led is super small, almost like a needle hole. It makes the light nicely non-intrusive.

Build quality is fairly good. No, you don’t get the thickest metal in the casing, but it’s not as if it’s a tin casing either. The front panel doesn’t quite align with the case on the sides – a small thing, but it might bug some people. The feel of the volume knob is great and this is one thing that I really feel is important, so they did a great job there. The power and input buttons feel crappy though, you don’t get any feeling if the device is on or not.




So what does this amplifier sound like?

I’ve spent enough time around real music instruments to know, that every single box in a stereo setup creates an interpretation of the real thing. Having flawless measuring figures does not make a perfect amplifier. In my opinion, every design topology implementation is an interpretation of the real thing in the end. So you might as well find a sound signature you like. That said, the THX 789 measures extremely well according to some measuring orientated audio sites.

So is it “a wire with a gain”? In some ways, you can call it that way. The background is dead silent with over-ear headphones (but not with super sensitive IEMs like the Campfire Andromeda Gold). There is a preciseness and cleanliness to the sound. Bass beats can seem almost edgy and have good impact with no bloatiness or fuzziness. It to me feels like it’s easy to separate instruments with these sound qualities. I think this works out extremely well with electronic music.

I’ve listened to many tube headphone amplifiers and I’ve definitely felt that there’s a sense of space in the sound. It’s probably harmonic distortion and warmth from the tubes, but it works for me. That sense of space is missing with the THX 789 however. Moreover, so is any other type of coloration. It’s a neutral sounding amp.




The Drop THX AAA 789 gives six watts to 16 and 32 ohm load headphones through the balanced output and that is very noticeable. The figures go down to 800 milliwatts at 300 ohms and 400 milliwatts at 600 ohms. The single ended output gives three watts to 16 ohms, 1,8 watts to 32 ohms, 200 milliwatts to 300 ohms, and 100 milliwatts to 600 ohms.

I have used the MrSpeakers Ether CX headphones with a 4-pin xlr to 3.5mm adapter. I tried switching from the balanced xlr-output to the 3.5mm single ended one , and yeah, there was a clear difference in sound quality. The Ether CXs are a power hungry headphone (23 ohms) and the difference was easily noticeable. With the single ended output playing Tipper’s Cuckoo, the bass notes didn’t have as much impact and definition.

Same case with the Audeze LCD-2.2 (pre fazor), they’re not easy to drive (around 60 ohm) either, but the amp has no qualms with them. I highly doubt this amplifier is able to drive Hifiman He-6’s to everyone’s volume needs, but that remains to be proved.


The Drop (former Massdrop) THX 789 is a wonderful headphone amplifier. Displaying a clean and precise sound signature with a black background and plenty of punch is not an easy achievement, but… at some point I know I’ll start to look for some type of coloration… Call it a flavor to the sound. But at the moment, I’m liking this flavor of preciseness.

4.2/5 - (100 votes)


  • Reply November 11, 2019


    Very well written article, Jana. If this is Jana D. I’ve read several other articles written
    by her for Stereophile, and she’s a very talented writer and photographer!

    Would love to see her contribute further articles to Headfonia in the future.


  • Reply November 11, 2019


    Very clearly and well written review. Very easy to read! Who needs four pages to deliver the bottomline, right?

    But, I’d like suggest a few tips to make your next professional review even better.

    – Headphone compability: It would be great to include at least dynamic, planar (both of what you used are planar) and IEM in order to cover more grounds. Also, including something like HD650 is always a good reference. I liked that you included LCD-2, which is another staple item among headphone lovers. But, I’d had love to read more about the experience in using it with the amp.

    – Source: Seasoned readers can benefit knowing from knowing what kind of music and DAC were used for the review. Even better, describing your musical experience can be helpful and make your review more illustrative.

    – Comparison: This is most important. Without a proper comparison to other headphone amps, it’s hard to defend the obejctivity of your review. A subjective review is good, but we can find plenty of those in Objectivity is what sets apart a professional from the pack. This is also where you demonstrate the experti in the product you are reviewing and gain the authroity. For ex, if you only have experiences with a few headphone amps, you shouldn’t be writing a professional review. But, by throwing out your experiences with the other good options readers are considering, you provide the utlity and gain the trust.

    – Details: I’m nitpicking, but it would be great to read what a clear difference you heard from phrase like “yeah, there was a clear difference in sound quality”

    Please don’t hate me for playing the devil’s advocate. But, I wish these comments will be helpful in your professional reviewer journey.

  • Reply November 11, 2019

    Esten Ray

    Great article I was thinking about buying theTHX headphone amp but this article sold me. I will try ordering one today. Very much appreciated the straightforward review and detailed description of this amp. Please keep it up. Thanks, sincerely Esten Ray.

  • Reply November 18, 2019


    Sometimes i prefer shorter, but more concise review with less info dumping. This is a quick read that goes to the point at page 1.great.

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