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THX Ltd. started as a company with a directive to ensure that upstream quality in cinema audio made it all the way to the audience in the theater.
In the movie theater, you need great power in order to get the dynamic range needed for impactful music and action...with a very low noise floor and low amounts of distortion in order to hear crisp dialog and all the detail in the recording.
Patrick Flanagan at THX is one of those quiet guys who goes about his business with an engineer’s mind and a craftsman’s attention to detail. You may have met him at a Head-Fi meet in California as Jude Mansilla has been able to have him offer some free headphone or IEM measurements to the community on multiple occasions.
We met him at the 2016 SF Head-Fi Meet where he provided us with some measurements of IEMs we were working on:
THX provides development and certification services to ensure that a whole range of audio products meet objective performance and quality metrics from frequency response to low distortion, with the goal of accurate sound reproduction.
The Massdrop x THX Achromatic Audio Amplifier (THX AAA™) 789 represents the next chapter in THX contribution to the audio world, where THX provides underlying circuit technology in the gear itself.
The new design was born of necessity. THX needed amplifiers to power line arrays of speakers in their facility. Class A topology amplifiers run too hot and are inefficient to run for long periods of time. THX needed the cleanest signal possible, low noise, low distortion, cool temperature, and efficient power consumption. These requirements led THX and SVP of Audio R&D Laurie Fincham to revisit negative feedback designs, figure out how to implement feed-forward correction, and create the quietest, lowest distortion amplifiers.
THX Ltd. At-A-Glance:
I. Highest quality sound for the utmost in cinematic experience (George Lucas’ original vision)
II. Development and certifications for pro audio and audiophile gear (people like Patrick)
III. Technological intellectual property in pro and consumer gear (Laurie Fincham’s amplifier design as an example)
A Series of Fortunate Events
If we didn’t talk about Patrick, you might not know that THX is working every day behind the scenes to provide information to companies making audio gear…with and without the THX logo. And if we didn’t meet Patrick, this collaboration might not have happened.
Meeting Patrick at the event pictured above led to our visiting THX and seeing some of the measurement labs plus their demo room. (Fun stuff and just happens to be walking distance from our office in San Francisco!)
Visiting their headquarters led to an invitation for a sneak peek of the THX AAA feed-forward topology during the Rocky Mountain Audio Festival in Colorado 2016.
We immediately saw the potential of this amplifier technology when we learned about it’s goals. Hearing the prototype- clean, clear, and natural (not sterile)...we knew that our community would like it too.
THX understands Massdrop’s connection with the headphone audiophile community and our drive to create custom-tailored products. THX collaborated with us to develop and bring this linear amplifier technology to you in this particular package, with the flexibility for in-ear monitors to large headphones. Capable for use in professional audio applications or for the audiophile that demands the most transparent upstream gear possible. This amplifier delivers the upstream quality of your music to your own personal headphone theater- in the comfort of your home or on your desk at work.
Massdrop x THX AAA™ 789 Linear Amplifier At-A-Glance:
I. Lowest THD in class – world class transparency
II. Extremely low channel crosstalk
III. From low to high power – for your IEMs and your hard-to-drive headphones
IV. Flexibility – from single-ended input/output to fully balanced throughput
V. Form factor and usability - small, cool, efficient energy consumption
VI. High value – high power and best performance at a low price point
By the way, we’re lucky to have Andrew Mason as a member here on Massdrop. Andrew is the THX expert in analog & power engineering who helped implement the THX AAA technology into our final product. If you have some technical questions about the amplifier, Andrew may just be around to answer them!
"If you have some technical questions about the amplifier, Andrew may just be around to answer them! "
What tool did the team use to measure @143dB down?
We use the Audio Precision flagship APx555. It's the only audio analyzer on the market capable of measuring distortion this low as it maxes out around -148 to -152 dB.
We've developed some special methods over the years and regularly collaborate with AP to squeeze the most out of the instrument. AP is using one of THX's AAA prototypes to demonstrate their 555 performance at various audio shows.
Thank you for the response.
I'm surprised to hear that the APx555 can measure that far down... that's a thousand fold improvement in power sensitivity over the advertised spec, if I'm not mistaken.
In my experience AP specs a "guaranteed minimum performance spec" that's super-conservative. Their instruments regularly blow it out of the water, especially the 555.
Hello and good day Andrew, could you elaborate and be a little more specific in how the measurements were taken? What FFT measurement bandwidth, bin width, window used, etc? Please be specific and technical; I'm an analog design engineer at a fabless semiconductor design facility that specializes in audio products. I'm quite interested in how these measurements were taken.
Hi Stevo. This is really about how to best configure the 555. I recommend we take this offline as it could get long. Connect with me on LinkedIn.
How can I connect with you on linkedin aswell?
I would also like to know if I were to use XLR inputs, could I use single ended output and/or RCA output? I know you answered the inverse question yesterday about single ended input with XLR headphone output.
Hi @Jimster480 . Yes! Using RCA or XLR-3 inputs will excite all 3 outputs to full power (3.5mm SE, 1/4" SE, XLR-4 balanced).
Just search my name and company on linkedin.
That is great news, but i was specifically asking about the XLR input with RCA output. So that I can stack this in-line with another amp or speakers.
My DX7 can only do RCA OR XLR output, otherwise it causes weird distortion noise and feedback (it warns against this in the manual). So Ideally I'd want to use my DX7->XLR output -> This Amp -> RCA Output -> O2/A30 Amp or my desktop speakers that I haven't gotten around to setting up xD
@Jimster480 unfortunately we need a relay network that selects the signal to be amplified based on the front panel "input" switch: either from RCAs, or XLR-3's. There's no connection between XLR-3 inputs and RCA inputs.
That's understandable, I'll just use rca then.
What 's up with the wal-wart ? Is it to save money ? Is it to save on size of enclosure, which I guess would go back to saving money and keeping cost down ? I really like the specs this amp has however the wal-wart and shipping time , I will wait on the thx-aaa amp thay monoprice has coming out.
Wall-wart power supply doesn't matter. But its actually a floor wart power supply lol. Either way its fine as other power supplies don't really have any sonic differences.
you can check the review of the D50 vs the DX7 or DX7s on audioscience review, the D50 got the best score despite having an external wall wart.
@lugnut Yep the external in-line power supply causes no sonic degradation vs an internal one, improves reliability, reduces retail cost, and speeds time-to-market. Plus there's additional merit to keeping the stray fields from the AC/DC away from the audio electronics.
The other product you refer to also has external AC/DC.
Some of the best sonic performing devices have external power supplies. This shouldn't even be a discussion.
are there published Blind tests?
Are the actual measurements posted on this discussion page not enough?
No, it's about how it sounds, not measures. Class D amps are a good example.
That all being said, I expect that this amp WILL sound very good. I'm just not waiting 8 months for the drop.
Measurements tell you everything you need to know about an amp. A well designed amp will not and should not color sound. All a blind test will tell you is if the reductions in distortion this claims to have is audible
Not all distortions are created equal.
Odd-order vs even-order.
Higher-order vs lower-order.
"The results of this study indicated that within the
constraints of this simple study that the perception of
linear distortion is dependent on the level and the
delay time of the linear distortion and the playback
level. The first two main effects were known as
indicated in the background discussion.. However,
while it may seem intuitively obvious, the significant
increase in the audibility of linear distortion has not
been shown before. Further, that this audibility of
linear distortion increase with both playback level
and with delay time is extremely important.
These results mean that a subjective impression
obtained where playback level was not controlled is
of questionable validity.
The combined effects of playback level and delay
have strong implications to the perceived perception
of nonlinear distortion. It is not possible to say,
without complicated objective tests, if what is being
perceived is a nonlinearity in the system or a
nonlinearity in the subjective perception as described
in this paper. This has profound implications to the
subjective evaluation of nonlinear distortion in audio
systems most particularly loudspeakers where the
delay factor can be quite strong.
Time delayed resonances, nearby cabinet reflections
and edge diffraction, waves in horns; all have delay
times on the same order as this study. A loudspeaker
that is evaluated at 70–80 dB (SPL) may have a very
different perception at 90-100 dB even if it is
A THD distortion curve will not reveal this effect,
nor will a frequency response graph. A careful look
at the impulse response might yield the best insight,
however this has not been quantified. Methods for
measuring the nonlinear effects of our subjective
perception are currently under investigation.
Another point is that the usefulness of a loudspeaker
for audio playback can have a sound power output
limit that is independent of its electrical power
handling or its nonlinear distortion characteristics.
Loudspeaker evaluations that take place at a fixed
level, are seriously inadequate at revealing the true
quality of these systems."
-Lee and Geddes; Audibility of Distortion; AES 121st Convention, San Francisco, CA, USA, 2006 October 5–8
And that is what we need to find out. If it's not audible what's the point of buying it over lowered cost equivalent. If people want to buy specs I have some 99.999% red paint, ordinary paint is only 99.996% red.
Was this developed before or after Razer bought THX?
I think before. The first news I saw on the THX AAA was 2015, iirc.
I had a $1400 Pathos Aurium that had one, had a lot of trouble with it. First everyone said it was the tubes, was not.
Ended up buy a aftermarket $$$ power supply it did fix the problem. It just was not with my amp either.
So before you say "well just because that company put out some bad ones, there not all bad".
That may well be true , however I will never buy a amp again the the external power supply. Also as far as " this shouldn't even be a discussion" Why should I not be able to voice my concerns about a subject that caused me problems.
"That may well be true , however I will never buy a amp again the the external power supply"
Where's the discussion? Sounds like a foregone conclusion.
I do think I added more to the discussion with my comments vs the person that said " This shouldn't even be a discussion ".
You shared an experience and a general complaint. The person that spoke of this conversation said:
" Wall-wart power supply doesn't matter. But its actually a floor wart power supply lol. Either way its fine as other power supplies don't really have any sonic differences.
you can check the review of the D50 vs the DX7 or DX7s on audioscience review, the D50 got the best score despite having an external wall wart. "
...before making the comment. I agree, discussion should always be allowed. But responding to hyperbolic commentary with hyperbolic commentary isn't really going to advance our conversation on the product or its design. There are, I'm sure, flawed wall-warts in the market place. But the question is, by analogy, whether or not you judge the Ford Mustang by the Ford Pinto, just because they're both Fords.
My issue with some wall-wort designs is based on the fact that it's a pain in the neck to use on a power strip. Floor-wart isn't as bad for me; at least there's room on the strip for more connectors. But then the length of the cable has to be sufficient for me to find somewhere to put the floor wart without just leaving it hanging off a wall or desk or something.
The RCA outs labeled "SE PASS".. are those at a fixed level, ie, useable for powered monitors + passive volume control?
same question, never got answered.
"They" are too cool to bother. None of my questions were answered either. In fairness - the amp is selling well so why would "they" bother?
Simple passthrough of DAC signal- so whatever your DAC outputs (2V?) that is just "passed" through.
Many people in headphone audiophile community like to have both a solid state and a tube amp of some kind to switch back and forth.
OK thanks CT. And to clarify.. is the SE PASS pass-through at a fixed and constant level, or is the SE PASS level controllable?
It is not fixed and also not controllable by the amp.
Volume control will not have any impact and there is no gain or attenuation placed on the signal.
Signal goes in the RCA inputs goes out the SE PASS as if there was a revolving door.
Whatever comes out of your DAC or other source will simply come out of the SE PASS RCA jacks.
This is just to give you ability to chain a source "to and through" the THX amp...
Hi, what is the use of the "auto off/bypass" switch please?
If you would like to save power and the unit is not used for a period of time, it will automatically sleep.
Thanks. Will the unit then turn back on with an input signal?
Hi @pospos . To turn back on requires pushing the Power button. We decided to not have "auto-on" feature since to do so without impacting fidelity, it would have required more relays and circuitry, driving the cost too high.
Of course if you prefer, set the switch to "bypass" mode and the amp will remain on forever.
Hi Andrew, do you have a measurement of left-right attenuation vs rotation? Purely objective question :)
ok, lot of questions. haha.
The power, distortion, etc specs say they are tested with 0db of gain, but the balanced output is not capable of even selecting that gain, its lowest is +6db gain. So are the specs listed under the balanced output measured at +6 or +0db?
Also, are the gains different for SE and Balanced simply because of how the balanced signal works? Or are they running through seperate circuits with different gains?
What is the voltage swing of the amp? I like seeing the power specs, but it is nice to know what the voltage is so I can judge how much current it also has behind that signal to be pulled when needed
Lastly, since testing was done with 300ohm load, does that mean this amp is "best suited" for that load?
I see you mentioned 12 ohm load as a minimum is fine, is that the amps actual recommended safe minimum?
Specs are listed for unbal output and bal output both at min gain setting. I.e. 0 dB and +6dB respectively.
Bal out gain is always 6dB higher to avoid necessity for a bunch of additional relays inside to swap gains around i.e. we wanted 3 configurations, not 6, with minimal gain/attenuation stages in the signal path.
You can compute the voltage swing vs load by using P=V^2/R. Peak current limit is around 0.8-0.9 Apk.
This amp is best suited for all headphones because: 1) Insane SNR, high Iout, and low Zout means excellent for IEMs. 2) Large Vswing means excellent for high impedance headphones. 3) High Iout, large Vswing, and low Zout means excellent for planar magnetics.
Hi SpeakFriend. Not yet. I'll add that to the backlog.
The specs are really fantastic, but I am suspicious about whether these are measurements of the underlying topology, or measurements of this specific Massdrop implementation . The single voltage DC-in implies the use of a rail splitter, and those kinds of measurements are pretty unheard-of with such a power supply implementation.
I'd love to hear your comments about that, and apologies if my assumptions are off.
We have two units out for independent measurement and verification.
Not just modules but the graphs from THX are measured from our amp samples.
Jude at Head-Fi.org has a sample and we hope for measurements from his APx555 soon.
The other is with Marv at SuperBestAudioFriends.com. I believe AtomicBob may be able to measure soon.
The specs are for the entire Massdrop 789 product. The AAA core amplifier on its own performs even better, but it's nice to have all the little features like selectable gain, volume control, ESD protection, DC protection, etc. etc.
And yes, we're using a THX-designed linear rail splitter to permit unipolar SMPS. Due to its feed forward error correction, AAA has nice side benefit of incredibly high PSRR to reject the small amount of ripple that escapes the splitter.
SE PASS RCAs are literally pass-through wires from one RCA pair to the other pair.
if the power is off, the se pass will not work, is that correct?
so if I line up other amps with 789, I have to keep it on and then pass throw the signal?
@baiyy1986 the 789 pass works regardless of power on or off. RCA input and RCA pass are always connected to each other. But critically, the input relay isolates the RCAs from the AMP and ESD clamp networks when power is off. So there's nothing in-circuit to clamp your RCA signals.
Are SE inputs converted to fully balanced output, or is only the hot or cold pin on the XLR output active?
Will Massdrop be releasing a speaker amplifier version of the THX AAA?
Full conversion to balanced output.
Looks really good. One thing that would make it even better for my purposes is a 2.5mm TRRS balanced headphone jack. While I could convert the XLR to a 2.5mm TRRS balanced with an adapter, it would be more elegant and handy to have a 2.5mm TRRS jack right on the amplifier. (The reason why I prefer the 2.5mm TRRS connector is because that is what my Onkyo DP-S1 Rubato portable DAP uses for it's balanced headphone jack, and it is a common jack on portable players from other companies as well such as Astell&Kern, Pioneer, etc. and at this point I've invested only in balanced headphone cables that terminate in 2.5mm TRRS.)
You could build/buy an adapter.
There isn't a standardized layout for balanced TRRS plugs. Some are R-,R+,L+,L-, (Fiio, Onkyo, A&K) some are L+,R+,L-R- (HiFiMan, others?).
I'm a little slow but we have reasonable 2.5mm TRRS to 4-pin adapters coming and they look nice...
"I'm a little slow, but..." Whoever gave CEE_TEE a thumbs-up for this ought to get a slap upside the head.
Is this the best headamp you've ever offered here?
Best is relative. To be more correct it would be the most linear amp.
If you extend this drop through 4/1, I can join it.
Do you have the reverse coming? I’m in a real need of a 4 pin to 2.5mm trrs converter
Andrew we need another drop, Monoprice's Dual THX788 Headphone Amp is delayed Oct and its been pushed out further twice :-(
Andrew whats the difference between 788 vs 789? Does have dual balanced 788's have greater quality, performance than what appears to be one 789 in this Massdrop version?
Please redrop! Was going to buy one and it has been on drop for days... just went off...
According to customer service, the drop apparently had a limit of 370 that I did not see a counter on, nor did I observe documentation of this limit listed for that matter. I need one of these for Christmas, how else can I get one or can you release more, asap, like today!?
Please keep an eye out in a couple of weeks...hope to have another soon!
Holidays... ruined, thanks Massdrop!
Holidays...enjoyed? Hopefully! :)
i also need to place another order. hopefully sooner then later
@CEE_TEE There is a large hole in the market right now for the perfect dac to match with this amp. I hope you realise that!
SOTA performance (SNR and distortion) with minimal functionality in a matching case and matching price is all you have to do.... :)
Oh Santa Massdrop when will you drop again?
They said Tuesday or Wednesday, I guess its Wednesday...
I received notice that the units arrived in the warehouse today.
Usually takes a few days to be checked in and ready to ship/sell.
With the holidays, we are hoping this is still the case and these will be up for sale next week.
Tracking these closely for you!
Woo! Yay, my wallet is ready!
Did you just do a mini drop? Or is one coming soon? If so how soon? I don’t want to miss out
No drop yet... I'm still waiting... it looks like next week now...
Interesting question. I'll be in the same boat.
And it’s on its way to me
Can I get free expedited shipping?
It is coming to my house now
@CEE_TEE Is there a product in the works which combines this and the SDAC into one unit ?
Not at the moment- we're getting the Balanced SDAC up and running first.
With all of the inputs and outputs on the Balanced SDAC in such a compact size, we think the community will be impressed and able to enjoy the SDAC-B in many combinations.
Especially with the Massdrop x THX AAA 789!
I know Massdrop loves the SDAC they helped create (probably cause its your only DAC right now?), but it really doesnt have the truly impressive SINAD specs to go with this THX amp. The SDAC really only measures just a bit better than a basic JDS Labs ODAC. Couldnt you get a project going with the specific goal of making a balanced DAC that sounds just as exceptional as this amp and has the THD%+N specs to match with this? Currently the closest thing (and it does come very close) to match with this THX amp in a similar price range would be this DAC:
That was my reaction as well, the THX 789 deserves a better than a good budget DAC. I'm using a Mimby with it ATM and would be interested in an upgrade later this year (it has to be later this year since buying the Elex and THX in the last month). Possibly the best match from MD would be the the Airist R-2R both in quality, price, and the added advantage of perfect stacking. My guess would be that this DAC is likely to drop again in the next few months, unless there is some problem with the IP issue, which probably also held sales down when it dropped earlier this year. I know the R-2R is not balanced (at least not yet) but it appears that a balanced DAC does not add that much to the THX given its topology. Another interesting possible upgrade would be the Topping D70, a fully balanced DAC with a ton of features that is expected to be released sometime in the next few months at $600.
Yeah, I was thinking the Airist was about the only MD product that seemed to match with this. Hmmm, good find on that D70... I've used the DX7 and an iFi micro-iDSD (both the original and black), all good but think I like the iFi a bit better.
When would the next drop be if any? :D
Also waiting for the next drop... ^^
No clue as to why it is taking so damm long.
@CEE_TEE you have to bring this back please. This drop wasn’t clear on limited stocks.
Poor us west coast people, 6am is not fair!
I saw this at 11pm(Singapore time), when the drop was available. Unfortunately I was in bed and thought I’ll book it the next morning when I wake up. If I knew it was limited, would have sprung into action.
Its kind of unfair.
I hope I’d be able to get one the next time.
next time could be months. I couldn't take it any more and ordered a JDS labs atom to tide me over.
If this drop was for preorder and these 500 units take 2-3 months to be manufactured, it means we ll have to wait till May for the next preorder-drop and we are lucky if we get our unit by the end of the year..
I didnt know that the manufacturing process takes so much time...
Hopefully something else appears meanwhile coz i m fed up waiting for this.
I 'd go for the Jds Atom also but it s not balanced
Any chance on the balanced dac being able to do MQA?
Andrew, what do you mean? Even if you are only using RCA inputs, if you hook up balanced headphones you will get the power benefits but not the "extra" balanced clarity?
Yes regardless of RCA or XLR input, all amp output are driven to full power (including the balanced output).
The "extra balanced clarity" people talk about might be due to reduced crosstalk, reduced hum, or high voltage swing inherent to bal-in/bal-out systems. With RCA in / bal out to the 789, you still retain the crosstalk reduction and high voltage swing.
Thanks! Two questions. Where can I find the online manual for the AAA 789? Why a preamp was not included? It would be especially useful, as most of us run powered monitor speakers where we could control with the volume knob. of the AAA 789. Now, we have to connect the speakers to the DAC, hoping its volume implementation is not cumbersome or use an external passive knob to control volume, since RCA outs are full power line level. It just seems like a big miss on this end...
There are a few reasons for not including a pre-amp out function on this amp. Would require additional switching on front panel or an auto-switching feature. Would require more outputs on the back panel and close to the power input circuitry which can get tricky with noise. We wanted to make the amp as flexible as possible for all headphone/IEM/driver tech/impedance listening use cases while also friendly to newer users: passthrough of the DAC will be at fixed line level and not blow out someone's new active monitors, easier to use/connect, lower cost of entry...but we hear you on pre-amp usefulness. Will bake it in where possible. Thanks for the input! Er, output. :)
We are definitely working on it, AndrewSim...thank you!
Thanks for Awesome product.
Was hunting last 5 months. Finally got it (even ordered two).
So, the next small request is to make a good balanced DAC in the same form factor, so a lot of people who bought AAA 786, Cavali and Liquid Carbon will buy it to match the stack setup. This market gap is still open and will be on high demand if you will make it as good as AAA-789.
Honestly I wouldn't care if it was just a Grace sdac in that shell at this point.
RME Adi-2 Dac appears to stack nicely with it, but short depth wise. That's my plan, but this is a really good idea and Massdrop would be foolish not to.
I've bought the RME Adi-2 Dac, but why?
They have already dropped one dac in the same shell, and they have dropped hints of another additional one fairly recently.
Why not brother! I have one and love it, couldn't resist getting a thx 789 for the price also. Is it May yet?
May is taking a long time!
I see mentions of May. Do we have reason to think that's when next drop will be?
May is when the last drop is scheduled to ship. May 17th from memory. I pounced on that $h1T as soon as I got the notification email. No one knows when the drop will be live again though. The Thx AAA789 seems to be quite the rare Pokémon. Sign up for notification and good luck!
Thanks . I didn't have enough $ so i didn't purchase immediately. Now i've had $350 sitting in PayPal account, waiting to pounce.
Are there any reasons or any future plans to release a second generation of the THX 789 AAA Amplifier ?
We're making more of the 789 as-is at the moment, but what would you like to see in another version?
I'd like some obvious indicators on the knobs. I don't have great lighting in my room, and I basically have to return the knob to 0 before listening to figure out what the volume should be when I switch headphones.
Maybe a second 1/4" jack to run a second pair of headphones, like Lake People often include. I want to side-by-side t50 mods but can't
Wonderful as it is now, maybe an indicators on the knobs so low-light isn't a guesswork?
The only other thing would be, seeing as how efficient the unit is from a heat perspective. Perhaps a design with an internal power supply? Or perhaps not incase it goes bust down the line, I suppose replacing a power cord with a brick is a far better solution as you currently have going.
Just please.. for the sake of everyone's sanity, could you comment on availability or anything pertaining to future timelines?
I believe the power supply is external for a reason, like interference..
My request would be a built in balanced dac.