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Review and Measurements of SMSL SP200 THX HP Amp

amirm

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#1
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:

SMSL SP200 THX Headphone Amplifier Audio Review.jpg

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:
SMSL SP200 THX Headphone Amplifier Back Panel Audio Review.jpg

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.

Headphone Amplifier Audio Measurements
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.

SMSL SP200 THX Headphone Amplifier Audio Measurements.png


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:

Best headphone amplifiers THX Reviewed.png


Referencing the same 5.6 volt output, the signal to noise ratio of the SP200 is fantastic as well:
SMSL SP200 THX Headphone Amplifier SNR Audio Measurements.png


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:
Quietest Headphone Amplifier Reviewed.png


Here is the gain level in the two modes and very good output impedance:

SMSL SP200 THX Headphone Amplifier Gain Audio Measurements.png


These are for XLR inputs which is what I used for all the tests.

Here is intermodulation distortion relative to output power:
SMSL SP200 THX Headphone Amplifier Intermodulation Distortion Audio Measurements.png


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:
SMSL SP200 THX Headphone Amplifier Power at 300 Ohm Audio Measurements.png


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:
SMSL SP200 THX Headphone Amplifier Power at 33 Ohm Audio Measurements.png


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):
SMSL SP200 THX Headphone Amplifier Power at 50 Ohm Audio Measurements.png


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:
SMSL SP200 THX Headphone Amplifier Channel Imbalance Audio Measurements.png


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.

Headphone Listening Tests
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.

Conclusions
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 is my absolute pleasure to recommend the SMSL SP200. It makes THX headphone amplifiers more affordable and gets rid of clutter on your desk to boot.

NOTE: this is a new product. 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.

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VintageFlanker

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#2
Thanks again @amirm. Looks like value is growing exponentially in the headamp world.:)
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.
More important to me: this one will be available for purchase!!
 
Last edited:

amirm

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#3
Yes and doesn't need to be imported into China for customers there. Hopefully availability in Europe, etc. is also good.
 

audimus

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#4
The exterior with those toggle switches take me back a few decades when I was building gizmos out of Radio Shack parts and enclosures.
 

amirm

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#11

Veri

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#12
Wow wow wow. I don't care how it looks that is crazy value! Also don't care about balanced not doubling power, on the massdrop one that boosted power to ridiculous levels.

Single ended with such high power and vanishing low noise is perfectly fine as far as my headphones are concerned.
 

Hugo9000

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#15
Thanks for the review! I would hope the crooked case was deliberate for this test unit, so they can identify this particular unit in any photos on the internet haha! My OCD couldn't handle owning something like that, my eye would be drawn to it constantly. The look of it is definitely a regression for SMSL, who have been making plain and clean-looking gear lately other than this poor "ugly duckling" with its fine performance haha.

Perhaps it's like auto manufacturers that have used disguises on prototypes for years, keeping the final look hidden from prying eyes until the official launch? :D

https://www.forbes.com/sites/michaeldunne/2016/03/10/car-spies-auto-camouflage/

https://jalopnik.com/watch-how-bmw-disguises-a-prototype-car-for-pre-product-1825243005
 

amirm

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#16
I should say that the pictures have geometric distortion due to angle I shot them. In reality, the slanted look is very slight and of course symmetrical on both ends. Here is SMSL's own picture:

 

Thomas savage

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#17
I should say that the pictures have geometric distortion due to angle I shot them. In reality, the slanted look is very slight and of course symmetrical on both ends. Here is SMSL's own picture:

How dose your measurements match up with theirs ?
 
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