Overview

The SMSL SU-9 Pro is a compact balanced desktop DAC built around ESS’s ES9039MS Pro D/A converter. It adds third-generation XMOS XU-316 USB processing, up to eleven OPA1612A op-amps in the analog stage, and full high-res support (PCM up to 768kHz/32-bit, DSD512). Notably, both USB and S/PDIF inputs support MQA and MQA-CD decoding, and Bluetooth 5.0 includes LDAC/aptX HD. [1]

Scientific Validity

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Independent lab measurements are available and confirm transparency-level performance. L7Audiolab provides a full test suite (including dashboards, linearity, multitone) for SU-9 Pro; their notes also flag minor digital-domain artifacts around certain jitter/12k tests. Reference Audio Analyzer (RAA) hosts a professional report with interactive plots covering FR, crosstalk, spectra, and more. Together these third-party sources substantiate that the SU-9 Pro performs audibly transparent within modern DAC limits. [2][3]

Technology Level

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ES9039MS Pro is a current-generation ESS part; SMSL couples it with the XU-316 USB interface (true 32-bit path), their CK-03 clocking, and an expanded OPA1612A output stage. Feature coverage is complete for a desktop DAC in 2025: balanced/unbalanced outputs, USB/optical/coaxial with DoP/DSD, LDAC Bluetooth, and a remote UI. [1]

Cost-Performance

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Comparator (cheapest equal-or-better): SMSL DO200 MKII — 469 USD.
Reason: balanced/unbalanced outputs, MQA/MQA-CD on both USB and S/PDIF, LDAC Bluetooth, and equivalent transparency-class performance; adds extra I/O (I²S, AES/EBU). [4][5]

CP calculation (policy formula):
CP = min(1.0, 469 USD / 499 USD) = 0.94 → 0.9

This score is adopted as the Cost-Performance evaluation.

Reliability & Support

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Warranty and support remain limited compared to major brands. SMSL’s official shop references a one-year factory warranty and retailer-mediated service; third-party retailer pages in the U.S. likewise list one-year coverage. Community reports indicate mixed experiences with RMA handling and regional support availability. [6][7]

Rationality of Design Philosophy

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SMSL pursues measurable transparency via modern ESS silicon, clean USB implementation, disciplined clocking, and a straightforward analog stage. Features like MQA on both USB and S/PDIF and LDAC BT serve practical use cases; there is no reliance on unverifiable or occult claims. [1][2][3]

Advice

If you specifically need MQA on S/PDIF as well as USB in a compact, remote-operated desktop DAC, the SU-9 Pro fits well. If value is paramount and you can accommodate a slightly larger unit with more I/O, the DO200 MKII at 469 USD undercuts the SU-9 Pro while meeting or exceeding its functional set. [4][5]

References

[1] SMSL — “SU-9 Pro” official product page, accessed 2025-08-18.
https://www.smsl-audio.com/portal/product/detail/id/805.html

[2] L7Audiolab — “Measurements of SMSL SU9 Pro ESS9039Pro DAC,” 2022-10-16, accessed 2025-08-18.
https://www.l7audiolab.com/f/smsl-su9-pro/

[3] Reference Audio Analyzer — “Measurement’s report: SMSL SU-9 PRO (Minimum Fast),” accessed 2025-08-18.
https://reference-audio-analyzer.pro/en/report//dac/smsl-su-9-pro-minimal-fast.php

[4] SMSL — “DO200 MKⅡ” official product page (specs incl. MQA on USB & S/PDIF), accessed 2025-08-18.
https://www.smsl-audio.com/portal/product/detail/id/803.html

[5] Amazon — “SMSL DO200 MKII MQA Balanced DAC,” current price 469 USD, accessed 2025-08-18.
https://www.amazon.com/dp/B0BF56VBTH

[6] SMSL Shop — “Warranty & Returns,” accessed 2025-08-18.
https://smsl.shop/pages/warranty-returns

[7] Audio46 — “Manufacturer Warranty Info (S.M.S.L 1 year),” updated 2025-06-27, accessed 2025-08-18.
https://audio46.com/pages/warranty-info

(2025.8.18)