Overview

The JM21 is a digital audio player built around dual Cirrus Logic CS43198 DACs and dual SGM8262 amps in a fully balanced path. It runs Android 13 on Qualcomm Snapdragon 680 with 3GB RAM/32GB ROM and features a 4.7” display, 4.4mm balanced and 3.5mm SE outputs, coaxial out, USB DAC mode, and Bluetooth 5.0 with LDAC/aptX HD/LHDC. The chassis is ~13mm thin and ~156g, with rated playback of ~12.5h (SE) or ~9.5h (balanced) [1][2].

Scientific Validity

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Figures are manufacturer specifications: balanced THD+N < 0.0006% at 1kHz/-4dB into 32Ω, S/N ≥129dB; frequency response deviation <0.03dB (20Hz–20kHz); crosstalk ≥110dB. Single-ended THD+N < 0.0012%, S/N ≥124dB, FR deviation <0.02dB, crosstalk ≥70dB [1]. These numbers indicate excellent transparency potential, but independent third-party measurements are not yet confirmed, hence the score.

Technology Level

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A solid, modern implementation: dual CS43198 with a fully balanced path, SGM8262 output stage, Android 13 on Snapdragon 680, and comprehensive wireless/streaming support [1][2]. The emphasis is on competent integration and high output (700mW+700mW at 32Ω balanced) within a thin chassis rather than novel circuit topology [1][2].

Cost-Performance

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JM21’s market price is 199 USD [2][3]. We could not identify any cheaper finished product that matches or exceeds its user-visible functions (Android with app installs, Wi-Fi/Bluetooth, 4.4mm balanced out) and published performance envelope. For context, HiBy R5 Gen 2 is 349 USD [4]; Shanling M3 Ultra is around 469 USD [7]; Sony NW-A306 supports Android but lacks 4.4mm balanced and thus isn’t an equivalent substitute [5]. Therefore CP=1.0 due to the absence of a cheaper equivalent-or-better alternative.

Reliability & Support

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FiiO’s global sales/support footprint and OTA update paths are documented [2]. As a 2025 model, long-term failure-rate data are not yet available, and durability of the ultra-thin build remains to be seen.

Rationality of Design Philosophy

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The product targets low distortion/noise and ample output within a mainstream SoC/OS platform and balanced output—an evidence-oriented direction [1][2]. While phone + dongle can replicate many functions, an all-in-one DAP still offers integrated power management, coaxial out, and tidy carry. The approach is pragmatic rather than novel.

Advice

Ideal for listeners who want streaming-centric Android usability and wired transparency from a single device. The rated performance, balanced drive capability, and Android 13 convenience make it a strong one-box solution versus juggling phone + dongle [1][2].

References

[1] FiiO, “JM21 Parameters,” https://www.fiio.com/jm21_parameters (accessed 2025-08-20). Key conditions: 1kHz/-4dB, 32Ω load, SE/Balanced, High gain; THD+N/SNR/FR/crosstalk values.
[2] FiiO, “JM21 Product Page,” https://www.fiio.com/jm21 (accessed 2025-08-20). Specs incl. thickness/weight, battery, outputs, codecs, operating modes.
[3] AV Watch, “FIIO『JM21』 entry model,” https://av.watch.impress.co.jp/docs/news/1657014.html (Jan 24, 2025). JP launch info and price guidance.
[4] HiBy, “R5 Gen 2 product/pricing,” https://store.hiby.com/products/hiby-r5-gen-2 (accessed 2025-08-20). 349 USD, Android, 4.4mm.
[5] Sony, “NW-A306 product page,” https://electronics.sony.com/audio/walkman-digital-recorders/walkman-mp3-players/p/nwa306-b (accessed 2025-08-20). Android support; no 4.4mm balanced.
[7] Linsoul, “Shanling M3 Ultra,” https://www.linsoul.com/products/shanling-m3-ultra (accessed 2025-08-20). Android 10, 4.4mm, pricing.

(2025.8.20)