This is a review and detailed measurements of the SMSL M500 MKIII balanced DAC and stereo headphone amplifier. It was sent to me by the company and costs US $530.

While the formfactor remains the same as previous generations, the display is upgraded to have high contrast and attractive color. Great that volume level if emphasized. The processor behind the display is also very performant with great volume control display rate and acceleration support. Navigation is simple using the included remote:

A couple of minor complaints though: the USB connector is too close tot he upside down XLR jack which made it impossible to push its pin in with the USB cable attached to right channel. Also, I like to see red for right channel on RCA connector. Otherwise, included power supply is much appreciated.

SMSL M500 MKIII Measurements
As usual we start with our dashboard using XLR out:

Most superb results! SINAD (sum of noise and distortion) is essentially tied with the best tested so far:

Distortion is exceptionally low with second harmonic at -140 dB! Just great.
Performance is nearly as good with RCA out:

Dynamic range is naturally excellent:

Intermodulation distortion+noise is superbly low:

Linearity is perfect:

Noise level with jitter is so low that the test signal's 250 Hz and multiples of 24-bit rightmost bit is clearly visible:

There is a tiny bit of low frequency random jitter that widens the "skirt" around our main tone. It is inconsequential from audibility point of view but seems like the USB clock could be a hair better in that regard. When using Toslink/Coax, that little issue goes away:

Multitone performance is superb:

Usual extensive choices of reconstruction filters are provided:

The default fast linear seems to be the best bet:

You get flat and extended response beyond 20 kHz.

This brings us to THD+N vs frequency which with default filter produced superb results:

SMSL M500 MKIII Headphone Output Measurements
Let's start with how much power we have into 300 ohm:

I like to see 100 milliwatts minimum and the MKIII clears that hurdle easily. It does that while looking really good with very low noise and distortion. Jumping to the other end of the spectrum with 32 ohm we see:

This is plenty good for the class with 1 watt per channel. No, it is not as powerful as dedicated amps in both measurements but should be good enough for vast majority of headphones out there.

Sweeping the load from 12 to 600 ohm shows stability and range of voltages you can use to compute the power:

There are only two gain levels: low and high. Without an ultra low (negative) gain, SNR at 50 millivolts is very good but not class leading:

SMSL M500 MKIII Listening Tests
I started testing with Dan Clark Expanse headphone which is difficult to drive with low impedance. Fidelity was to die for with superb detail and good enough of power. Mind you, this was in high gain and max volume. Switching to Sennheiser HD650 naturally provided much higher output with comfortable (loud) listening level of -7 dB. At 0 dB volume, you could get that sensation of subwoofer in your head with sold bass rattling my head for the one second I had it at that volume. Sound quality was once again exceptional (within the bounds of the HD650 response).

Conclusions
The Mark III revision of M500 improves on both looks and performance of this balanced DAC. In that subsystem, everything you could ask for is provided as far as performance. The headphone amplifier matches that overall but is a step down from total power point of view compared to what you can get. For most applications involving headphone use though, you should still be all set.

It is my pleasure to recommend SMSL M500 MKIII.