Overview

The SMSL D300 is a desktop DAC built around ROHM’s BD34301EKV. It supports PCM up to 768kHz, DSD512, balanced XLR and RCA outputs, and Bluetooth 5.0 with LDAC reception [1]. Multiple retailers list the D300 as discontinued/sold out, which limits new-unit availability despite ongoing documentation on the official site [3][4][1].

Scientific Validity

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Independent measurements show the D300 achieves transparent performance for human hearing: SINAD around 114?116dB via balanced outputs, with excellent linearity and low jitter in third-party testing [2]. Manufacturer specifications state THD+N as low as ?116dB and dynamic range circa 127dB (XLR), aligning with transparency thresholds for DACs [1]. Together these indicate the D300 reproduces the master signal transparently under normal use.

Technology Level

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The design integrates established building blocks (XMOS XU-208 USB interface, CK-03 clocking, standard balanced output stage) around ROHM’s BD34301EKV [1]. There is no evidence of notable in-house DSP, patented techniques, or advanced software integration. Given contemporary designs have moved to newer USB controllers (e.g., XU-316) and similar or better performance is common, the D300’s technical originality and recency are modest.

Cost-Performance

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Current representative price for the D300 is 399 USD (denominator). The TOPPING E70 offers equivalent or better user-visible functions (balanced XLR, Bluetooth with LDAC) and superior measured performance (ASR measured ~123dB SINAD) [2][5][6]. Its current market price is 279 USD [5].
Calculation: 279 USD ÷ 399 USD = 0.699 → CP = 0.7 (rounded to one decimal).

Equivalence note: E70 equips XLR outputs and LDAC Bluetooth and meets/exceeds D300 on core audible metrics (THD+N/SINAD, dynamic range) based on third-party data [6].

Reliability & Support

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Warranty terms are typically one year depending on seller/region (SMSL shop lists a one-year transferable factory warranty) [7]. With the D300 discontinued at major retailers, long-term parts/firmware support is uncertain for new buyers [3][4]. The all-solid-state, no-moving-parts architecture is inherently simple, but the short warranty and product discontinuation reduce the expected support horizon.

Rationality of Design Philosophy

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Prioritizing a premium DAC chip without clear, audible advantages over numerous cheaper, transparently measuring designs leads to low price-to-performance efficiency. Investment appears skewed toward chip prestige rather than measurable, user-relevant improvements (e.g., markedly higher output headroom, novel DSP, or integration). Given the market’s rapid movement to devices with equal or better performance at lower prices, the design direction is only moderately rational.

Advice

If you can find a new D300 at a fair price, it will deliver transparent conversion and convenient LDAC receive mode. For most readers, however, the TOPPING E70 at 279 USD provides equivalent functions and superior measured performance at a lower price [5][6]. If you prefer to stay within SMSL, the DO200 Pro at 399 USD also measures at the state-of-the-art and remains actively sold [8]. Given discontinuation risk and shorter warranty norms, prioritize models with ongoing availability and verified third-party measurements.

References

[1] SMSL, “D300 – Product Page,” https://www.smsl-audio.com/portal/product/detail/id/771.html, accessed 2025-08-28. (Specs incl. LDAC, PCM 768kHz, DSD512, XU-208, THD+N ≤116dB)

[2] Audio Science Review, “SMSL D300 Review (Balanced DAC),” https://www.audiosciencereview.com/forum/index.php?threads/smsl-d300-review-balanced-dac.28919/, accessed 2025-08-28. (Third-party measurements, balanced outputs)

[3] Apos Audio, “SMSL D300 Desktop DAC (Discontinued),” https://apos.audio/products/smsl-d300-dac-digital-to-analog-converter, accessed 2025-08-28. (Status: discontinued; historical pricing)

[4] Bloom Audio, “SMSL D300

USB Bluetooth Desktop DAC – Discontinued,” https://bloomaudio.com/products/smsl-d300, accessed 2025-08-28. (Status: discontinued)

[5] Amazon (US), “TOPPING E70 DAC – LDAC Bluetooth 5.1,” https://www.amazon.com/Decoder-ES9028PRO-Bluetooth5-1-Digital-Analog-Convertor/dp/B0BKG8FVP5, accessed 2025-08-28. (Price ~279 USD; LDAC support)

[6] Audio Science Review, “Topping E70 Stereo DAC Review,” https://www.audiosciencereview.com/forum/index.php?threads/topping-e70-stereo-dac-review.39188/, accessed 2025-08-28. (Measured SINAD ≥123dB)

[7] SMSL.shop, “Warranty & Returns (Factory warranty One-Year Transferable Warranty),” https://smsl.shop/pages/encountering-problems-while-using, accessed 2025-08-28.

[8] Audio Science Review, “SMSL DO200 Pro DAC Review,” https://www.audiosciencereview.com/forum/index.php?threads/smsl-do200-pro-dac-review.60095/, accessed 2025-08-28.

(2025.8.28)