SMSL SU-9 DAC/Preamp Review – This is the Modern World

Writing for this blog yields us neither love nor money (and we certainly don’t need any more gear), so we cling desperately to our journalistic integrity and often refuse offers to review stuff unless we’re convinced there’s no quid pro quo. Ergo, fearless leader Jürgen put Apos Audio through a merciless inquisition and set of conditions before deigning to allow them to loan us their intriguing products, of which the $439.00 SMSL SU-9 DAC/Preamp is the first to arrive.

Unexpectedly unimposing and lightweight, the SMSL SU-9 nonetheless packs a ton of connectivity options into a paperback-book sized package, including balanced outs and Bluetooth. Supported codecs are off the hook—UAT, MQA, AptX and virtually every other acronym you can think of. A single front knob controls both volume (when using in variable mode) and the numerous sound-shaping menu options; I found it so intuitive that I didn’t use the included remote. Unlike many of its price peers, the SMSL SU-9 does not have an onboard headphone amp (perhaps the next generation will?). It does, however, function as a digital preamp.

The SMSL SU-9’s main gimmick is its user-selectable options for PCM and DSD filters and for “sound colors,” which are basically DSP modes intended to modify the timbral characteristics of the DAC. I found the PCM and DSD adjustments to have little audible effect, although they will surely please more obsessive technophiles. The sound colors are subtler than the  EQ modes contained in most DAPs or phones– I didn’t hear a ton of differentiation between the default “Standard” setting and the Tube settings, although the Crystal setting registers as a little edgier and more treble-emphasized, while the Rich mode seemed to impart  some added warmth and had the most unforced natural tonality.  (Note: for the most part I utilized the Rich mode on a variety of CD, FLAC and 328kB Spotify files; amps/preamps used included an old Proton D540, an Arcam FMJ A39 integrated, a Rotel RC1572 pre, an Acurus A150 and a Parasound HCA-1000a).

However tuned and paired, the SMSL SU-9 isn’t a paragon of neutrality—it is  a punchy, energetic source with a lean note texture. Midrange, in particular sounds somewhat boosted.  Tonality is a little bit warm/smooth, albeit without sacrificing much clarity. Instruments are very well-articulated—there’s no blurring between frequencies and attack is very fast, which makes the presentation sound clean and uncompressed.

The SMSL SU-9 stands out in two respects. First, because it imparts an aggressive presence across the frequency spectrum, it excels for low-volume listening—music doesn’t simply fade into background but retains drive and character even when turned down. Second, bass control is impeccable—low end is impactful but wholly without bloat. This is particular noticeable when paired with warmer, softer amps like my Arcam, which can obscure details on more complex materials.

The SMSL SU-9 wholly outguns its predecessor in my office system, the $250 Maverick TubeMagic D2, which has  a smooth, analog sound but is much less revealing. The SMSL SU-9 had much more oomph and presented more detail, as well a much quieter background. To some extent, this is attributable to the SMSL SU-9’s more advanced chip (the D2 seems capped at 96k), but even lower bitrate Spotify files sound crisper and more transparent on the SMSL SU-9.

The $550 Chord Mojo is a closer match—the Mojo sounded more transparent and truer to the source than the SMSL SU-9, but lacked the SU-9’s dynamics and slam. The Mojo seemed to have more air between instruments, which gives it the sense of a wider soundstage; however lower-quality files sounded less harsh and unrefined on the SMSL SU-9.  Overall, the Mojo had the crisper, more detailed presentation while the SMSL SU-9 was sweeter and silkier; your preference will likely depend upon equipment pairing and source material.

All that said, I was most impressed when using the SMSL SU-9 as a preamp and Bluetooth streamer; the SMSL SU-9 sounded much cleaner than my Arcam and less bright/glaring than the Rotel pre  it replaced in my home system.  Background on the SMSL SU-9  was dead quiet and volume control was commendably precise; subjectively at least, Bluetooth had more body and dynamic range than typical and sounded about as good as wifi on the same files. I rued how much money and real estate I could have saved if I had started out with this little box and some powered speakers instead of the mounds of equipment and stacks of discs I’ve accumulated.

Undoubtedly you could drop a couple of grand on a DAC with a higher level of resolution or timbral purity. But the SMSL SU-9 in certainly a considerable step-up from entry-level and registers as a lot of technology for the money.  I’m inclined to buy myself one for Christmas.

Disclaimer: Apos loaned me this unit for review; it was passed on to my colleagues before being returned to Apos.

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