This is a review and detailed measurements of the SMSL SP200 THX technology headphone amplifier. It was recently announced and company was kind enough to send me a sample. SMSL tells me the retail cost will be US $289.99. This would place it in the middle of the pack of our reference quality headphone amplifiers. The JDS Labs Atom costs US 99. The recently announced and reviewed Monoprice Monolith THX costs US $400. And the one that started it all, Drop THX AAA 789 also costs US $400.The SP200 came in a generic box which tells me final packaging is not yet available. From the outside, it is larger than JSD Labs Atom but smaller than the other two:Yes, the box is not quite rectangular. I am hoping this is a quirk of this sample and not representative of the final packaging.The connectors look high quality and switches have a solid feel that the two more expensive units do not have. There are only two gain settings, rather than three that they sport however.Volume control is smooth but feels a little less nice. Certainly a big step up from JDS Atom but its small size and slippery feel makes it a bit hard to turn. May want to get an aftermarket one with better feel if that bothers you.The main story believe it or not, is in the back:Do you see it? This is the first reference quality headphone amplifier with an included AC power supply! No external dongle to worry about.The included power supply also gives the unit quite a bit of heft making it feel quite solid.My favorite, XLR inputs are included which can be of a great help in avoiding ground loops with your PC and DAC.No pass-through though connectors but you can use the front panel for that purpose if you wanted.Speaking of the front panel, I forgot to highlight inclusion of both XLR and 1/4 inch jack. As testing will show, these are connected to the same output so no increased power from XLR connector. Use it for convenience.I am told the SP200 will be available for sale on October 25th, 2019.For consistency with previous measurements, I fed the SP200 4 volts and measured at 5.6 volt. Performance is almost the same if I had used unity gain with 4 volt of output.Yes, we have another winner on our hands! Distortion products are at or below whopping -130 dB. That makes them completely inaudible in all circumstances since best case dynamic range of our hearing is around 115 dB. You have quite a bit margin here to not degrade the performance of your DAC.So SINAD which is signal over noise and distortion is really determined by noise level. Here, my analyze is contributing some to it so actual performance is even a bit better. As it is, the SP200 easily classifies as reference quality headphone amplifier:Referencing the same 5.6 volt output, the signal to noise ratio of the SP200 is fantastic as well:However, its baseline noise must be higher as it doesn't do as well when the output is hugely reduced to just 50 millivolt to represent driving sensitive IEMs:Here is the gain level in the two modes and very good output impedance:These are for XLR inputs which is what I used for all the tests.Here is intermodulation distortion relative to output power:In low gain, performance is neck and neck with Drop's THX 789. It actually produces the same power as that unit despite use of low gain.Switching to high gain (blue) gives us even more power but comes at the cost of higher noise. Note that this test uses the volume control at maximum which you would not normally use. So the real life performance of high gain will be better than is shown.Here are the most important tests of any headphone amplifier: power into various loads starting with 300 ohm representing high-impedance "voltage hungry" headphones:We see the same thing as in IMD test. We have tons of power on top even in low gain to tune of 200 milliwatts. My threshold here is 100 milliwatt and the SP200 doubles that which is excellent. High gain increases that to 326 milliwatt.Going to the other extreme with 33 ohm load for "current hungry" headphones, we get similar results:As a side note, when I designed this test, I did not think to turn on the low-distortion mode of my audio analyzer thinking it was not needed. It actually is here! When I turned that on (not shown) distortion at the bottom right was even lower. For consistency, I am leaving it the same but you should note that with this setting, the distortion of my analyzer is the limit, not these headphone amplifiers!Next, I compared the low and high gain using 1/4 inch headphone jack and XLR at 50 ohm (using different fixtures):As noted, we don't get more power using XLR output. That is fine with me. There is no benefit to "balanced output" anyway on headphones. And we have tons of power here, albeit less than what the Drop THX AAA 789 can produce.Channel imbalance was good giving use a lot of attenuation before the matching goes crazy:Being analog in nature, there are some variations along the way. And will likely be some unit to unit variation. If you want precise matching to the end for sensitive IEMs, you should get a DAC+headphone amp.My torture test for headphone amplifiers is the closed back Drop Mrspeakers Ether CX which drop.com was kind enough to send me for testing. It has a low impedance of just 25 ohm making it very current hungry. With the SP200 I had to go to high gain to have all the headroom I wanted. Near painful levels were achieved at 12:00 to 2:00pm on the volume dial, being fed unbalanced from my Topping DX3 Pro line outs.Next I switched to Sennheiser HD650. Performance here in one word was superb. I am actually listening to it right now even though testing is finished! Crazy bass dynamics are available in high gain past 12:00 pm. Even in low gain you get very good volume.THX seems to have revolutionized the mid to high-priced headphone amplifier market. It provides a winning combination of vanishingly low distortion and tons of power. Only JDS Labs has been able to keep up with it with Atom. We used to have one choice in THX amp which was drop.com and its notoriously poor availability. Now we are at the cusp of having two more options in the form of Monolith and SMSL SP200.Great to see a new price point also in THX amps. You can add a $100 DAC to SP200 and still be cheaper than the other THX offerings.Needless to say,It makes THX headphone amplifiers more affordable and gets rid of clutter on your desk to boot.As with any new product, there may be delays in production, early teasing issues, etc. I can only vouch for the audio performance of the SP200. You need to do your own due diligence for other factor before purchasing.------------As always, questions, comments, recommendations, etc. are welcome.Realizing that he only gets used for superb products, the "hit it out of the park" pink panther is cornering the market and demanding a pay raise! So pleasehim before he quits and goes to my competitor using : https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/