Overview

SU-9 Ultra is a balanced desktop DAC built around AKM’s AK4191 + AK4499EX with XMOS XU-316. It offers USB/optical/coaxial inputs, balanced XLR and single-ended RCA outputs, LDAC-capable Bluetooth, and MQA/MQA-CD decoding over both USB and S/PDIF. It supports PCM up to 32-bit/768kHz and DSD512, positioning it among today’s transparent DACs in practical use [1][6].

Scientific Validity

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The published numbers—THD+N 0.00006% (-124dB), SNR 132dB (XLR), XLR 5Vrms / RCA 2.5Vrms—are comfortably below audibility thresholds, i.e., in the “transparent” region. As of this writing, no comprehensive third-party lab suite for SU-9 Ultra was located, so this is a provisional assessment based on manufacturer specifications and established engineering context; we will incorporate independent data when available [1][6].

Technology Level

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The architecture (AK4499EX+AK4191 with separated digital/analog domains, XU-316 true 32-bit USB, CK-03 clocking, discrete linear regulation) reflects competent, modern implementation. While proprietary disclosures are limited, the integration is coherent and technically sound [1].

Cost-Performance

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Reviewed unit price (denominator): 499 USD [4].
Cheapest equivalent-or-better comparator: Topping E70V (E70 Velvet) with LDAC Bluetooth, balanced XLR/RCA, PCM768/DSD512; third-party measurements show transparent-class performance (≈121dB SINAD) [2]. Current new price observed at 349 USD (Amazon) [3].

Computation: 349 USD ÷ 499 USD = 0.70 → rounded to 0.7.
Equivalence note: LDAC BT, balanced outputs, PCM768/DSD512, and transparent-region THD+N/SINAD qualify it as equal-or-better from the user’s perspective [2][3].

Reliability & Support

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Manufacturer warranty is commonly 1 year globally (EU regions may see 2 years; some retailers advertise extended coverage). SMSL maintains download/support portals for drivers/firmware. Net: average to slightly positive outlook on reliability/support [5][7][4].

Rationality of Design Philosophy

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Resources are directed toward measurable transparency and user-facing functionality (LDAC BT, MQA, balanced outputs) without conspicuous non-scientific claims. It’s a pragmatic, measurement-aligned design approach rather than a marketing-driven one [1].

Advice

If you need a transparent desktop DAC with flexible inputs (USB, TV/coax, optical) and balanced outputs, SU-9 Ultra is a safe pick. XLR 5Vrms plays nicely with active speakers or external preamps, and XU-316 ensures robust USB behavior. If MQA isn’t critical and budget matters, note that E70V achieves a comparable transparent endpoint at a lower price today [2][3][4].

References

[1] SMSL, “SU-9 ULTRA,” https://www.smsl-audio.com/portal/product/detail/id/894.html (accessed 2025-08-28). Key specs: AK4191+AK4499EX, PCM 768k/DSD512, MQA/MQA-CD, LDAC/aptX HD/AAC/SBC, CK-03, XLR 5Vrms/RCA 2.5Vrms.
[2] L7Audiolab, “Measurements of Topping E70 VELVET DAC,” https://www.l7audiolab.com/f/topping-e70-v/ (published 2022-12-11; accessed 2025-08-28) [ZH].
[3] Amazon, “TOPPING E70 VELVET (New price 349 USD page),” https://www.amazon.com/dp/B0DNJKZYH2 (accessed 2025-08-28).
[4] ShenzhenAudio, “S.M.S.L SU9 ULTRA… (499.99 USD),” https://shenzhenaudio.com/products/s-m-s-l-su9-ultra-ak4191-ak4499ex-digital-to-analog-convertor-dac (accessed 2025-08-28).
[5] Bloom Audio, “Manufacturer Warranty Information (SMSL 1 year),” https://bloomaudio.com/pages/manufacturer-warranty-information (accessed 2025-08-28).
[6] Apos Audio, “SMSL SU-9 Ultra MQA High-Performance DAC (specs),” https://apos.audio/products/smsl-su9-ultra-dac (accessed 2025-08-28).
[7] SMSL, “Support (Manual/Driver/Firmware),” https://www.smsl-audio.com/portal/product/support (accessed 2025-08-28).

(2025.8.28)