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Drop + THX AAA™ ONE Linear Amplifier

Drop + THX AAA™ ONE Linear Amplifier

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Product Description
We teamed up with THX to build a leaner version of our beloved 789 amplifier. With THX AAA technology, three gain stages, and a new preamp output, the Drop + THX AAA ONE has all the essentials, and nothing extra.

Customer Reviews

(144 reviews)
95% would recommend to a friend
Mar 8, 2021
Drop was kind enough to send me the THX AAA One amp for review, so I've put together an article and video that I'll link below. The following is an excerpt from the full review, but big thanks to Drop for sending it in for evaluation.
"As the name suggests, the THX AAA One Linear Amplifier has a linear, reference style sound - one that’s reminiscent of its bigger brother the THX 789. It’s extremely clean sounding with a totally dead background, regardless of the headphones being used. One point of difference between the One and other lower end amps is that while they can often get loud enough, they don’t do anywhere near as well for the sense of space, image separation and distribution, with more of a focus on center image.  Comparing the One with certain budget DAC/Amp combos meant more for portable use like the Khadas Tone2 Pro (also around $200) was a night and day difference for overall sense of lateral definition, with the One handily beating the Tone2 Pro. Of course, this is maybe an unfair comparison given that the One has a much larger footprint and isn’t meant for portable use - but it still does reveal the benefits of a full sized desktop amplifier like the One over these other smaller devices. So, the One’s focus is on accurate soundstage and space, while remaining analytic and articulate - again, other amps do this as well, but not all. Comparing it directly with the Schiit Audio Magni 3 Heresy and the Topping L30, the One again seemed to do a better job of filling in the lateral space for front left and front right. I feel as though it’s not actually enhancing the soundstage, but rather giving sounds that fall left and right of center better definition and presence, contributing to an enhanced sense of ‘fullness’. Additionally, I find the One to be more analytic than what I’m used to at this price - nothing gets smoothed over and you get all the information. Once again, this sounds like a reference class amplifier, and in my mind that’s a very good thing. Who It’s For As mentioned, the THX AAA One is extremely versatile, as it can power medium hard to drive headphones, and highly sensitive IEMs without noise floor issues whatsoever. For that reason, the One is for those who have varying power requirements for different headphones - or those who own both over-ear headphones and IEMs, and want the convenience of not having to use different devices for both applications.  Moreover, the One is also for those who frequently forget to turn off their equipment when done using it. I say this because the One doesn’t get warm, making it fit nicely in a stack. There’s also an additional feature/quirk with the One that it seems to power down or go into sleep mode without having to toggle the power switch. When you start to play music again, there’s a small click and then it powers itself on again after half a second.  Lastly, the One is for anyone looking for that transparent, analytic presentation that gives you all the information, similar to what you get with the THX 789." Read the rest of the article here: Watch the video review here:

Recommends this product? Yes
Mar 10, 2021
Thanks for the review , I have a L30 and getting a 789 in a few days , so I will skip this for now , hope you do shootout vudeo between such like under 200$ amps. Love your videos and big fan 😁
Mar 10, 2021
I think I just heard a mic drop...yep...that’s why it was...a mic drop.
Jul 17, 2021
checkVerified Buyer
Replaced my Asgard
I bought this amp on a hunch & am pleased that I did. I'm currently running a Gustard X16 with Audeze LCD2CB headphones and have owned way too much other gear to list. The short.. I think these THX amps are as clean as the $1K Bakoon amp I bought on Drop a decade ago with stronger dynamics(although auditory memory is fickle and I've changed a lot of gear since then so YMMV.) I'd also take this over the Schiit Heresy I owned last year; I'm not confident I could tell them apart but the build quality is nicer here. I don't like having an amp light enough that I can rip it off my shelf. Longer story is that I was running an Asgard 3 when I took delivery of the ONE, here are my impressions: Pros for the Drop AAA One Linear
  • Replacing the A3 with the Drop shows a more studio clear(cold?) atmosphere where the A3 engulfs you in warm backdrop, I struggle to describe this trait as it's almost secondary to the music but extremely important to me. This is the main reason I'm making the change over. IME the whole system needs to be capable of this crispier/colder atmosphere or it just ends up sounding warm. Every R2R or AKM velvet DAC I've owned has made previous clean amps sound more like the A3 in this regard.*
  • The A3 sounds notably rolled off up top(and further recesses the Audeze uppermids) in comparison. The overall dark sound of my system combined with the above has been killing my enjoyment of music as of late. I doesn't sound right for modern recordings(metal music.) In spite of the fact I prefer my music a touch softer/forgiving my enjoyment of such is dependent on a brighter shimmery treble; using EQ to drive the treble higher on the A3 just makes it loud without any hint of the sunlit sound I'm shooting for.
  • The Drop amp is faster or maintains superior resolution of complex passages however I do think the A3 in low-gain is sometimes faster in the bass, the THX amp is doing something I can't quite put words too where the bass can't always keep up with the upper ranges. The A3 is coherent across the range.
  • The Drop can do hard cracks with kickdrums whereas the A3 slams. Both are on equal footing in macrodynamics trading blows with different tracks. My attention is more often called to the Drop's dynamics in general.
Pros for the Asgard 3
  • The Asgard takes its share of wins as well having a more interesting timbre & the slightest extension to note decay rendering the sound more correct or live sounding.
  • The A3 is the thicker more wall-of-sound style amp, despite my specific preferences I acknowledge this may make it the better rock/metal amp in general. The Drop is thinner in tonal weight and this can take away the powerful feel of heavy music. This also gives the A3 more forward momentum(even more so in high-gain which further thickens the sound.)
  • The Drop is guilty of over-separating notes which is likely just a side-effect of its great speed rather than a unique trait, I may just be repeating what I wrote in the previous section but the Drop renders tremolo picked guitars more a string of quickly picked notes while not offering kickdrums the same instead blending them more together. The A3 is more continuous with its rendition which makes it an easier listen.
  • While both amps have provided satisfying all day listening in my system I did hear sibilance once from the One. It may be more prone to harshness(I have a high tolerance for brightness so this may crop up more with others.)
These amps are close competitors and equally matched to my ears. The choice will come down to preference.
Recommends this product? Yes
I've been using the Drop + THX AAA One (we got a better short name for that? the One?) for about a month now. I'll be honest, my thoughts on amps are usually pretty brief, but Drop sent this for review so I'll do my best to be articulate. I'll also be live streaming a review on my Super* Review YouTube channel soon (, so smash that like button, etc., etc. Review is now live. Watch it on YouTube. While I generally hold that if you want to improve your sound, you'll get more by changing your headphones and your music, once you've got those settled it's worth optimizing your amp situation. In my experience... most amps sound about the same. There are certainly a lot of things an amp can do wrong: Severe coloration, audible noise floor, high output impedance, etc. But most decent amps get those things right and achieve what I'll call "sufficiency," at which point I'm personally going to prioritize things other than pure sound quality, like output power, functionality, price, aesthetics, and knob feel.

Does the One achieve sufficiency? You bet. It's a good-sounding solid-state amp. Twist my arm for more detail and I might start saying things like "it's very neutral -- clean, with a starkly black background and sharp definition." Which tells you not much, except that this does seem to be an amp catered toward the objectivist measure-minded folks. I'm thankful for the work the measurers do, but mostly for calming that nagging doubt we audiophiles often give too much sway. I haven't measured the One, but I expect it'll be similar to the 789 -- inaudible THD, strong SINAD, or whatever numbers are supposed to assuage our doubts. I did some head-to-head comparing with a couple of other amps I have. One is the Schiit Vali 2 (which is not for objectivists) and the other is the JDS Atom (which is). I never loved the Atom, but not because it doesn't achieve the aforementioned sufficiency. It measures objectively well, and sounds about as good as I should want from an amp. But it's in a cheap-feeling plastic box with plastic knobs, and if I told you that those things make it sound worse to me, I'd only be half kidding. The Schiit Vali, on the other hand, I do love. It's metal, looks like it was handmade in a garage, its tube glows, and it gets hot. Do those things make it sound better? Not literally. But they do make the experience of amping my headphones more satisfying. The One is also a metal box. I like that. It's got a significantly larger footprint than the Vali or the Atom, and I don't mind that. It's heavy enough that it doesn't move around during most use, though not heavy enough to keep it from sliding backward when plugging in a chunky quarter-inch headphone cable. All of the buttons and knobs on the front appear to be metal. The gain switch clicks positively, and the volume has decent knob feel, about the same level of mild-scratchiness in the Vali knob, and about the same 300-degrees of rotation. The One doesn't seem to get hot, even when left on throughout the day. My only strong complaint in this silly-but-real category of things that determine "how I feel about this box" is that I wish there was a matching DAC. Drop sells some DACs that ostensibly will pair perfectly well with the One, but are aesthetically inconsistent. The Schiit stuff sure stacks pretty. OK, if you're not convinced by that, I'll make some substantive claims about the sound. I have a hard time hearing a difference between the Atom and the One, but I do get a hint of blacker background and sharper transients on the One. Could be placebo, but I did my best to fool myself with blind A-B and I could just barely make out the difference. I wouldn't make my purchase decision based on this difference, it's so minute. The Vali, however, is a more obvious difference. In comparison to the One, the Vali is a bit relaxed in the lower treble, and has a character that seems to somewhat expand the staging. Or perhaps more elaborately put, the Vali seems to fill the space between instruments with air, where the One sounds more like the space is compressed via vacuum. Probably, I am descrbing the effect of THD, which is audibly-high on the Vali. Which should be objectively worse, but I think the difference is more a choice of taste. And in this comparison, I think the sound difference is worth considering in a purchase decision. So like I said, the One is a "very neutral" option. Is that boring? Only if your music is. Some other points worth making in a review of the One:
  • On low gain, I detect absolutely zero hiss with my most sensitive IEMs. (On high gain with the volume cranked, I can start to hear some hiss.)
  • One oddity: With the volume knob turned to zero, I can still hear music playing faintly in my headphones. Not enough to bother me, it's barely audible... but odd.
  • No obvious channel imbalances with the volume knob at its lowest settings -- that's good. (This is a somewhat common problem with other amps, and can bother sensitive IEMs.)
  • The One has pre-output on the back. Output is switched via a button on the front, and the pre-out volume level is affected by the gain switch and volume knobs.
  • There's an auto-sleep (and auto-wake) function built into the One. It's a nice feature, makes it easy to leave the amp switched on.
  • The amp takes approximately two seconds to "warm up" when powered on (or awakened from sleep). Much faster than my Vali, but it's not instant.

  • Oh, power output -- there's plenty! I primarily tested with Sennheiser HD 600 and Hifiman Sundara. They're not the most power-hungry, and indeed they're powered easily by the One. I don't have a 789 to test, but on paper the One is actually MORE powerful compared to the 789's single-ended output. And as a basic single-ended kinda guy, that's better for me.
Recommends this product? Yes
Jun 4, 2021
mrsalleeSpeaking of things that an amp can do wrong...If the 1kΩ (1000 ohms???) INPUT impedance isn't a misprint, & I suspect it's the truth, OF COURSE this amp will sound "clean" to the point of "sterile". AND have "a touch" of "glare" and/or hardness to the sound quality! What does it matter if an amp has .000000000000% distortion on its own, only to throw the source components feeding it into an apoplectic fit of 99% distortion due to SLEW LIMITING since other line level output stages of DAC's, phono preamps, streamers, etc. ARE NOT DESIGNED TO WORK PROPERLY WHEN TERMINATED BY A SHORT CIRCUIT!!! And I'm supposed to believe that some other Poster's el-cheapo vintage Japanese integrated amp's (the Sansui AU-6600) pre and/or line outs can properly cope with feeding an input impedance FIFTY TIMES lower than what it was designed for??? That it sounded "good" to either of you??? For one thing, was there even ANY bass? The 1000Ω input impedance of "The One" is barely twice the impedance of some Pro high impedance phones; why not/may as well just get an RCA to phone jack adapter & just connect your phones directly to your music source! Save $195 or so, & eliminate the 0.00000001% distortion of this BADLY DESIGNED PRODUCT in the process! :) Yeah, I know why they made the input impedance so retardedly & inappropriately low... Because TIN EARS obsessed by S/N Ratio numbers can claim the circuit is quieter when you short-circuit the input as opposed to when the volume control resistance is actually something realistic like 47,000Ω or higher... OF COURSE your amp is alot quieter when you turn the volume right down to near 7 o'clock instead of say, 10 o'clock which would be a typical listening setting! Poor THX, instead of claiming their IMAGINARY "140db S/N Ratio" (Duck! Incoming flying pigs!) they would have to settle with claiming a mere 125db S/N Ratio instead! WHAH! If this stupid amp was actually designed to be listened to & sound good, as opposed to merely winning the specsmanship space race to be the world's quietest $200 door-stop, I'd seriously consider buying it. I also don't understand a Pre Out feature for something with only one set of input jacks. Not that I own a 20% distortion pair of powered computer speakers that would audibly benefit from being driven by a 0.0000000001234% Headphone Amp.... They took the balanced XLR headphone output jacks for THAT??? OK, not that someone with a $6000 pair of Abyss cans would EVER want to listen through a cheap piece of AUDIO DEATH with them, "nice knobs" & "metal box" aside! More importantly, was the preamp out REALLY a better idea than including another headphone jack, like say, a 3.5mm one??? Or even having more than just one headphone jack??? And if you're going to have a preamp out, you REALLY ought to have at least 3 sets of input jacks, & a 3-position rotary switch to select between them! What sort of "Purist" is served here??? Somebody who spends $200 to NOT listen to headphones, but wants a cheap gizmo to test the limits of his Audio Precision System One or SYS-2722? C'mon Dropheads! You aren't fooling me! This was a joke at $350 paid in advance with delivery 6 months later, when the first of these AAA-789's practical jokes were first offered to us. And I'm still not getting the joke...
Jun 8, 2021
NottagorillaThank you for your feedback!) But what alternative do you see for the same $ 200?
Oct 5, 2021
checkVerified Buyer
Best Budget SE Amplifier currently available
I am so impressed with the THX AAA One Linear amplifier. The sound is detailed, clear and controlled all the while presenting in a pleasing manner. The amplifier walks the balance beam between work and pleasure; meaning it doesn't veer into being overly analytical or to warm and lush. It reveals all the nuances of any DAC it is paired with. There is plenty of power for the majority of gear available. The THX AAA One Linear has two little gripes from me; first is that it lacks just a touch of air and space; second is that it rounds edges of notes and details; both of these little gripes means that the amplifier lacks just a touch of naturalism. The Geshelli Labs Archel 2 Pro isn't able to present on the same level nor does it have the power. The only standalone amp that I have had in house either for review or I own that beats the THX AAA One Linear is the the HeadAmp GS-X Mini which is my reference amp for all reviews. I would take this over any of the SMSL or Topping amps that I have heard and reviewed. In fact, even though it doesn't have balanced input or output, I would take it over the Topping A90. Gear used: Mytek Liberty DAC Schiit Audio BiFrost 2 Matrix Element X Hifiman Sundara Kennerton Gjallarhorn Hifiman Ananda MrSpeakers Ether C Audeze LCD-X Rosson Audio Design RAD-0 Sennheiser HD600 Sennheiser HD660s Geshelli Labs Archel 2 Pro In my opinion, the THX AAA One Linear amplifier is all that one would need for a budget setup. I highly recommend the DROP + THX AAA One Linear Amplifier to anyone.
Recommends this product? Yes
Feb 20, 2023
I've not heard or used the HE6. I doubt it would have enough to drive them to their potential but I've not had the pleasure to try that pairing.
Feb 21, 2023
dbsylviaThanks dbsylvia, appreciate the honesty. I ended up with the Monolith by monoprice THXAAA balanced featuring 887 tech. Monoprice has it on sale for $249...Hope it's enough. 😉
Mar 19, 2021
checkVerified Buyer
Linear asf
If you are looking for linear and single-ended, this is the best option on the market. I have had a great experience with this amp so far. The gain knob and volume knob both feel very premium. The 1/4 in. jack I can tell is sturdy. The pre-amp out is great for powered speakers. Allows for a seamless transition from headphones to speakers when you have these at a desk. Perfect amp for my use case. There's not a single feature of the amp I don't use but there's also not a single feature I wish would be added to this amp. It's absolutely everything I need and nothing more.
Recommends this product? Yes
Dec 30, 2021
checkVerified Buyer
Exactly what I was looking for
This is my first amp, and will probably be my last, with this little amp living up to its name - the ONE. I bought it to see how much of a difference an amp would make with my 58X, and to give me something to drive higher end headphones if I ever want to upgrade. The ONE does help open up the 58X and bring out some elements of the music that are not as well presented with just onboard audio. I was originally running straight out of my MacBook, but recently purchased a Schiit Modi 3. The ONE pairs excellently with the Modi, and the stack should comfortably handle any headphones I am ever realistically likely to purchase. Others have found that middle gain is not loud enough, but I am pleased with the volume. I'm not a very loud listener, usually, and about 1 o'clock on the medium gain setting is sufficient for my normal listening with the 58X, whereas I needed to pump the onboard volume to 80-90 percent of max when running straight out of my laptop. Build quality is excellent, and the ONE has a clean, smart look that I like a lot. The gain selector has a satisfying click, and the volume knob also has a quality feel and resistance level. I don't currently use the preamp output, but I love that feature and plan to add speakers to my setup down the line. The switch will make it easy to just plug and play. Overall, a great product, especially at the sale price. At 200, it's a fair price, but I'm not sure it's worth the difference over something like a Magni Heresy, according to the general opinion of the audiophile internet. On sale, I think it's a great deal.
Recommends this product? Yes
Jan 9, 2022
Thanks for the advice! I've been eyeing Sundara and Elex for a bit. The ONE appealed to me since it will support an upgrade like that nicely. Hoping to try one or both soon and get more out of the amp.
Jan 16, 2022
TedPThe ONE only sounds as good as the equipment that you use it with. I give a lot more info on how to get the best sound in my review here: You can't go wrong with the Sundaras. They're awesome. But, the Anandas are the ones to ultimately aim for if you have the funds.
Jun 8, 2021
checkVerified Buyer
The One very considerate
I have acknowledged that Drop + THX AAA One is not the cheapest, smallest, nor most powerful choice out there. However I really appreciate its additional features those are not found in others. It offers preamp function with a separate switching button that allows switching modes without unplugging headphone jack. And its 0.25x low gain offering is also a virtue for my specific audio circumstance. I also like its size, metal case, overall slick black look, small and light power adapter, and even the power button located front (not like Schiit's toggles behind). I'm just very happy with my first and only THX amp. I also own and listen with JDS, ifi Zen, Asgard 3, A50s, and some others, then if I have to get rid of all and can keep only one headphone/preamp, Drop + THX AAA One is the strongest candidate so far.

Recommends this product? Yes
Mar 26, 2021
checkVerified Buyer
Better bass than my fireflies.

Mar 21, 2021
checkVerified Buyer
Well made, looks good and sounds great for the price
I finally had some time to hook up the THX AAA ONE amp to my setup. Here is a short review. My first impression is that this box looks like a little jewel. It's classy and it feels very solid - straight out of the box. It's beautifully made. It has just the right weight to it to make it feel like a robust piece of audio gear - how can I say?... it just looks right to me. The knobs are a little smaller than I expected. They are longer than they are wide. But after a few hours of listening and playing with the ONE, I'm already getting used to the size and the simplicity of the front panel's layout. The amp has been running for more than 3 hours and the case is still very cold. You'll have no worries if you plan on putting your DAC on top of it. My gear Just to give you an idea of the possibilities of having this headphone amplifier in your setup, I have the ONE's Input hooked to the RCA Line Output of a vintage Sansui AU-6600. With its multiple inputs, it's very practicle in my setup. Whether they are a DAC, a turntable or a receiver, I can select whicheverby the simple turn of a knob and choose to listen to my source on either headphones or two pairs of speakers. A pair of YAMAHA MSP5 are hooked to the ONE's PRE OUT which does a good job if I need to listen headphone free without having to power ON the AU-6600. THX AAA ONE +... Vinyl? So far, I tested the ONE with a few vinyl records and I can say it sounds absolutely superb. As my source, I have the latest Technics SL-1200 MK7 hooked to the AU-6600's phono stage. Although I have not tried the Technics' internal phono stage, I'm sure any turntable equiped with a Line OUT hooked to the ONE would do the job just as well. For this setup, I find the ONE to be a very good match. I can also use it with the AU-6600 turned OFF since it has a bypass Line Out circuit. Streaming As I'm writing this, I'm listening to a few high-res files from the Neil Young Archives and I'm quite impressed by the very detailed, open and clear sound. Everything sounds just right to my ears (audio is so subjective). And, I'm only using the FX-Audio DAC X6 as my DAC. Headphones I tested the ONE with a pair of HD-58x (150 Ω), my trusty Sennheiser HD-560 Ovation II (300 Ω) and a pair of Grado SR-125e (32 Ω) to test the SE OUT. To my ears, the Grados are the best match for this amp. They are the only ones out of the three headphones that I can set to position II on the gain selector. Otherwise, position II doesn't seem to have enough power to decently drive 150 Ω + headphones. But switch that knob to position III and everything just sounds great again. Conclusion I think DROP and THX did a great job with this ONE. I'm giving this amp a 4 ½ stars and not 5 stars for the only reason that I would've liked it to have an extra fixed level Line Out. Other than that it's just perfect for me. It's very well made and sounds great for the price I paid.

Recommends this product? Yes
Mar 12, 2021
checkVerified Buyer
This drives my Focals much more dynamicly than my mytek brooklyn. I was immediately impressed by the bass and the overall sound. Great piece of kit.

Recommends this product? Yes
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