Overview

The SMSL SD-9 is a network digital music player (transport) supporting local storage and network streaming (DLNA/AirPlay), with I2S (HDMI), AES/EBU, coaxial, optical, and USB digital outputs, Bluetooth TX/RX, and HiBy Link app control. Manufacturer specs state up to 32-bit/384 kHz PCM and DSD256 over USB/I2S, and DoP/D2P options on S/PDIF. These features, especially the combination of I2S and AES/EBU at this price, are uncommon among streamers. [2][3]

Scientific Validity

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As a digital transport, audible differences mainly hinge on interface behavior (e.g., jitter) rather than analog metrics. Audio Science Review measured the SD-9 and noted elevated jitter spurs versus best-in-class but characterized them as likely not audibly concerning; a 24-bit 1 kHz dithered tone also showed harmonics that slightly reduced SINAD. Overall, the unit delivers bit-perfect data and functions adequately, but measurements do not demonstrate clear audible advantages over competent alternatives. [1]

Technology Level

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The SD-9 uses established technologies (SoC + clocking/CPLD, dual-band Wi-Fi, standard streaming protocols) and does not present novel DSP, room correction, or software innovation. The inclusion of both I2S and AES/EBU outputs is practically useful but not inherently advanced. Therefore, implementation quality appears industry-average with no unique technical breakthroughs claimed in public materials. [2][3]

Cost-Performance

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Current market price is 344 USD (typical new street price). To assess CP, we looked for the cheapest product with equal-or-better user functions and measured-relevant digital outputs (specifically, network streaming plus both I2S and AES/EBU). Matrix Audio element S (I2S + AES/EBU) and HoloAudio RED (I2S + AES/EBU) both qualify functionally but are substantially more expensive (around 1,499 USD and 798–878 USD, respectively). Cheaper streamers like the WiiM Ultra lack I2S/AES-EBU and thus are not equivalent. As no cheaper equivalent-or-better product could be identified, CP = 1.0 by definition. [4][5][6][7][8]

Reliability & Support

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SMSL provides a standard warranty via dealers and has issued firmware updates for network products historically, though cadence varies by model. The SD-9’s digital-only signal path implies fewer aging components than analog gear, but long-term update/support horizon is typical for this class and brand; no abnormal failure data is publicly established. Overall, an average showing for warranty and support. (General brand/product information.)

Rationality of Design Philosophy

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Focusing spend on a compact transport that exposes multiple digital outputs—including I2S and AES/EBU—has clear system-integration logic for users with external DACs that accept these inputs. However, absent advanced DSP/room features or demonstrably superior measured performance, the approach is functional rather than groundbreaking. Claims remain within conventional engineering without resorting to non-scientific narratives. [2][3]

Advice

Choose the SD-9 if you specifically need both I2S and AES/EBU from a network transport at low cost—there is no cheaper single-box streamer providing this combination as of the review date. If you do not need I2S/AES-EBU, cheaper streamers (e.g., WiiM Ultra) can offer broader convenience (app ecosystem, preamp/DAC features) at similar or lower prices, but they are not functionally equivalent regarding digital output formats. If you need additional processing (room correction, EQ, multiroom), consider higher-end platforms or adding software on the playback side. [4][8]

References

[1] Audio Science Review, “SMSL SD-9 Player Review,” https://www.audiosciencereview.com/forum/index.php?threads/smsl-sd-9-player-review.44801/, accessed 2025-08-28.
[2] SMSL (official), “SD-9 product page (EN),” https://www.smsl-audio.com/portal/product/detail/id/751.html, accessed 2025-08-28. Key specs: USB/I2S up to 32-bit/384 kHz PCM & DSD256; I2S via HDMI; S/PDIF DoP/D2P; HiBy Link.
[3] SMSL, “SD-9 User Manual (PDF),” https://doc.soundimports.nl/pdf/brands/SMSL/SD-9/SMSL%20SD-9.pdf, accessed 2025-08-28. Noted: I2S/SPDIF selection; fixed-rate output; DSD output modes; AES listed under SPDIF.
[4] Apos Audio, “SMSL SD-9 HiFi Network Music Player,” https://apos.audio/products/smsl-sd-9-hifi-network-music-player, accessed 2025-08-28. Price reference ~343.99 USD new.
[5] Apos Audio, “Matrix element S Music Streamer,” https://apos.audio/products/matrix-element-s-streamer, accessed 2025-08-28. Outputs include I2S + AES/EBU; price ~1,499 USD.
[6] Matrix Audio (official), “element S | Music Streamer,” https://www.matrix-digi.com/product/90/element_S, accessed 2025-08-28. Confirms AES/EBU + I2S outputs.
[7] Kitsune HiFi, “HoloAudio RED – DDC & Network Streamer,” https://kitsunehifi.com/products/holoaudio-red-ddc-network-streamer-1, accessed 2025-08-28. Confirms I2S (HDMI) and AES/EBU; price listed ~878 USD.
[8] WiiM (official), “WiiM Ultra – Overview & Specs,” https://www.wiimhome.com/wiimultra/specs and https://wiimhome.com/wiimultra/overview, accessed 2025-08-28. Notes max 192 kHz/24-bit and absence of I2S/AES-EBU outputs.

(2025.8.28)