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Starting points: Drop + THX’s AAA 789 Linear Amplifier

  • In this series of ‘Starting points’ posts, we’re looking at more affordable headphone amplifiers. We’ve already given the Pro-Ject Head Box S2 (US$149) and Schiit Asgard 3 (US$199) the once over. Today we step up our spend by another hundred bucks to take in the Drop + THX AAA 789 Linear Amplifier (US$299).

    Yep, that name is a mouthful, so let’s decode a bit. Drop, formerly known as Massdrop, started as a sort of group-buy facilitator for hobbyist equipment. Over time the company moved into collaborative efforts where the gear was commissioned specifically for them. This particular amplifier was made in conjunction with THX and features their Achromatic Audio Amplifier – AAA for short – which claims extreme transparency to the source material. The 789 appears to be the actual model number for this amplifier, and “linear amplifier” is the general descriptor. Whew. I’ll just refer to it as the 789 for simplicity’s sake.

    The 789 is part of the Drop Studio collection which means it should generally be available to purchase now, rather than being available on a group buy system with its associated delays. Like any other Drop product, it could sell out from time to time – particularly due to Covid-related supply-chain issues. But at the time of writing this amplifier is in stock and Drop’s intent is to keep it that way.

    Drop refers to the 789 as “the world’s most linear amplifier”. That sort of hyperbole is a bit polarizing in nature, but there’s no doubt this is, in fact, a very advanced design. I’m not going to rehash all the technical info available on their product page but I do have a quick clarification about the “balanced” nature of the design. The 789 gives us XLR inputs and a 4-pin XLR headphone out, but is it really balanced throughout? THX engineer Andrew Mason advises:

    “The signal path internally is fully differential throughout (per Putzeys), but is NOT truly balanced in a few sections. We preserve the full signal integrity but we avoid increasing the retail price for no measurable benefit.”

    Like many other headphone amps, the 789 might more accurately be called “pseudo-balanced”, but that doesn’t mean it isn’t worthwhile. Its 4-pin XLR headphone jack offers double the output of the single-ended for a maximum of 6 Watts into 32 ohms. And the 789’s XLR inputs take full advantage of a DAC’s balanced outputs, like those found on the DA Art Aquila II.

    The sound here is indeed strikingly clear. This is most noteworthy in the treble, which on a great recording can sound truly lifelike. But the 789’s sense of clarity permeates the rest of the frequency spectrum. Transient response is ultra-fast and controlled, which becomes particularly noteworthy on busy music: from piano virtuoso Hiromi Uehara to electro pioneer BT to the punishing complexity of Fleshgod Apocalypse. Factor in the 789’s inky black background and we get a jaw-dropping experience. If you want to hear each distinct note reproduced with extreme precision – and if your headphones can keep up – the 789 amplifier should be your first choice among this group of four starting points.

    “A wire with gain” is the term that comes to mind. When it comes to technical performance, the 789 doesn’t only leave our baseline Pro-Ject amplifier for dust, its performance approaches lofty designs such as the Pass Labs HPA-1 and HeadAmp GS-X mk2, both of which play in a completely different price class. Put simply – I’ve never heard an affordable amplifier do speed and accuracy as well as the 789.

    Zooming out, the overall presentation leans toward the intimate with exceptional imaging tied to a rather small soundstage; width – and particularly depth – are limited in reach. Despite each instrument being accurately placed, there’s not a great deal of breathing room. This is more of an issue with large-scale orchestral works and opera than it is for jazz and other recordings made in smaller spaces. Based upon my own listening habits, this is a long way from being a deal-breaker but it’s something to think about.

    The 789’s technical prowess with transparency places inordinately high demands on the rest of the chain. It will more readily expose flaws in any source component. The use of a US$1500 transport/DAC combo feels perhaps overly generous with the other reasonably-priced amplifiers covered in this series of posts, yet it seems almost mandatory for the 789 to really shine.

    Recording quality therefore also becomes an issue. After meandering through classics like Bitches Brew, Dark Side of the Moon, OK Computer and various Reference Recordings releases, marvelling at their clarity and speed, I then hit up the seedy underbelly of my collection. Bad Brains. Cannibal Ox. Pedro the Lion. King Crimson’s Earthbound. These are obviously not “audiophile” recordings and I can still enjoy them with most gear…but the THX 789 really tests my commitment. Every wart, every flaw, comes through as clear as day. This is most certainly not the amplifier to forgive any weaknesses in a recording.

    The Drop + THX AAA 789 has a lot going for it. The enclosure is quite attractive if perhaps a bit utilitarian. Functionality is excellent, with the robust connectivity plus three-stage gain selection that, at last (!), gives us more headroom with sensitive IEMs. It’s powerful enough to drive anything and seems to pair best with significantly more expensive headphones – a sure sign of this amplifier transcending the “budget” category. Listeners chasing enhanced bass impact, a creamy midrange or some other fun coloration might find the 789 somewhat arresting but those seeking the limits of brutal honesty will be handsomely rewarded.

    Further information: Drop

    Next up, the Feliks Audio Echo.


    Hardware notes

    For this review, I used the US$700 DA Art Aquila II, a DAC that gives us single-ended and fully balanced outputs along with a beautifully transparent sound signature that doesn’t strangle the headphone amplifier’s performance. The Aquila II, running in “pure DAC” mode (full-scale output, no volume control) was fed by a Cayin iDAP-6 transport (US$799). I switched out my usual reference Audio Art cables for the more affordable Better Cables Silver Serpent line, which starts at $99 for a set of interconnects. I also ditched my relatively expensive balanced power conditioner in favor of a simple Yulong Audio P18 ($329) which provides 4 x clean AC outputs – plenty for the simpler system being used. All in, perhaps still a bit more front-end than necessary, but at least I know the amplifiers aren’t being held back.

    As headphones go, I did not limit myself to budget or even midrange models. I find that using a high-end headphone with even modest amplification typically sounds far better than flipping things around and using a top-level amplifier to drive more affordable headphones. I made full use of my entire headphone collection to identify synergistic pairings as well as poor matches.

    John Grandberg

    Written by John Grandberg

    John Grandberg is a US-based audio journalist who has been immersed in the scene for over a decade. A recovering percussionist, he has a particular affinity for headphones and associated gear.

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