This is a review and detailed measurements of the brand new SMSL SU-9 Balanced USB DAC. It was kindly sent to me by one of their distributors, Shenzhenaudio. The SU-9 will be released September 30th and will cost US $439.99.

The SU-9 has a simpler but in my opinion more elegant look than previous SMSL DACs:

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The display is now larger and courtesy of its fine resolution, nice to look at. The rotary control lets you navigate the menus by pressing and rotating. Alas, I could not figure out how to get out of the menus and had to wait for it to time out. Perhaps there is a way but not having read the manual, I did not know how.  There is a remote of course which would make this simpler.

Back panel is what you expect in this class DAC plus addition of Bluetooth:

Power supply is included of course eliminating the external bricks that come with lower cost DACs. And of course balanced XLR output which I highly encourage for computer connected DACs.

DAC Audio Measurements

As usual, we start with our dashboard view:

Wow! Another DAC nearly maxing out the distortion+noise meter in my analyzer! The SINAD of 120 dB puts the SU-9 way up there in rankings:

Zooming in:

Note that the SU-9 is capable of output above 4 volts which is nice. To show the performance at other output levels, I ran a sweep:

Since the SINAD measurement is noise limited (distortion alone is at 130 dB SINAD), having the output higher helps improve it as you see it in the above graph.

IMD distortion versus level shows excellent performance:

Our old friend the "ESS IMD Hump" is still there but 90% suppressed.

Linearity which is a measure of accuracy is perfect:

Jitter over USB is non-existent:

There is a digital PLL that helps reduce jitter but since there is none with USB input, it makes no difference. It however helps with Toslink jitter:

There may be a latency penalty though so if you are using Toslink for TV sound input, you may need to play with that. Fortunately the jitter that was there with default setting was not an audible concern anyway (at -120 dB and heavily masked by the signal itself).

Lots of filters are provided for any taste (imagined or otherwise):

I like that there is a proper brickwall filter. I used that for the following test:

There is some frequency dependency here. I ran an FFT (not shown) and it showed that to be "imaging" components that were changing way up in frequency so not an audible issue.

Finally, multitone test showed how low the distortion is in SU-9 DAC:

EDIT: forgot to include the dynamic range in the original review:

And output impedance versus frequency:
RCA:

XLR:

Be sure your amplifier has an input impedance above 3.7k Ohm (10 to 1 ratio) for XLR output and half and 1.3 k for RCA.

Conclusions
Looks like we started a trend to achieve perfection in desktop DACs and the SMSL SU-9 is yet another example of that. We have another great "instrument grade" DAC on our hands providing absolute transparency to the source beyond any threshold of human hearing. If you are hearing issues I suggest you either have your hearing examined, or learn to do a proper controlled test. Either way, what you hear is what is on your recording. Guaranteed!

It is my pleasure to highly recommend the SMSL SU-9. Great job.