The FiiO JM21 is a portable player at $199. It delivers 245 mW into 32Ω and 30 mW into 300Ω, which ranks it 148 of 280 for raw power among the sources in this database.
Measured at 100 dB SPL it has comfortable headroom on 548 of the 567 dynamic and planar headphones catalogued here, enough but not generous on 17, only marginal on 1 and not enough power for 1. FiiO's budget sub-brand player, running Android. Note that FiiO publishes power for USB-DAC mode only — there is no rating for it working as a standalone player.
The manufacturer publishes 360 mW into 16Ω, 245 mW into 32Ω, 30 mW into 300Ω. The rest of the table is worked out from those.
The balanced output is rated separately: 700 mW into 32Ω through the 4.4mm jack.
Derived rows hold output voltage steady, as an amplifier does (method).
| Load | Power | Status | How it was arrived at |
|---|---|---|---|
| 16 Ω | 360 mW | Published | the manufacturer publishes this figure at this exact load |
| 32 Ω | 245 mW | Published | the manufacturer publishes this figure at this exact load |
| 150 Ω | 56 mW | Derived | worked out between two published loads, holding output voltage linear between them |
| 300 Ω | 30 mW | Published | the manufacturer publishes this figure at this exact load |
| 600 Ω | 15 mW | Derived | beyond the published loads, holding output voltage constant — which understates rather than flatters |
Easiest to hardest to drive, with headroom at a 100 dB SPL peak.
| Headphone | Impedance | Sensitivity | Needs | Headroom | Verdict |
|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 114.0 dB/mW | 0.04 mW | +37 dB | Comfortable audible hiss |
| 64 Audio U12t | 12.6 Ω | 108.0 dB/mW | 0.16 mW | +33 dB | Comfortable audible hiss |
| Shure SE215 | 17 Ω | 107.0 dB/mW | 0.20 mW | +32 dB | Comfortable faint hiss |
| Moondrop Aria | 32 Ω | 107.1 dB/mW | 0.19 mW | +31 dB | Comfortable faint hiss |
| Audeze LCD-X 2021 | 20 Ω | 103.0 dB/mW | 0.50 mW | +28 dB | Comfortable faint hiss |
| Truthear Hexa | 20.5 Ω | 103.1 dB/mW | 0.49 mW | +28 dB | Comfortable faint hiss |
| Sennheiser IE 200 | 18 Ω | 101.6 dB/mW | 0.69 mW | +27 dB | Comfortable faint hiss |
| Sony MDR-7506 | 63 Ω | 106.0 dB/mW | 0.25 mW | +27 dB | Comfortable faint hiss |
| Meze 99 Classics | 32 Ω | 103.0 dB/mW | 0.50 mW | +27 dB | Comfortable faint hiss |
| Focal Clear MG | 55 Ω | 104.0 dB/mW | 0.40 mW | +26 dB | Comfortable faint hiss |
| Philips SHP9500 | 32 Ω | 101.0 dB | 0.79 mW | +25 dB | Comfortable faint hiss |
| Focal Utopia | 80 Ω | 104.0 dB/mW | 0.40 mW | +24 dB | Comfortable |
| Meze Empyrean | 32 Ω | 100.0 dB | 1.0 mW | +24 dB | Comfortable |
| Campfire Audio Andromeda 2020 | 9 Ω | 94.0 dB | 4.0 mW | +17 dB | Comfortable |
| Etymotic ER2SE | 15 Ω | 96.0 dB/mW | 2.5 mW | +21 dB | Comfortable |
| AKG K371 | 32 Ω | 99.1 dB/mW | 1.2 mW | +23 dB | Comfortable |
| Audio-Technica ATH-M50X | 38 Ω | 99.0 dB/mW | 1.3 mW | +22 dB | Comfortable |
| Beyerdynamic DT 900 Pro X | 48 Ω | 100.0 dB/mW | 1.0 mW | +22 dB | Comfortable |
| Audeze LCD-2 Classic | 70 Ω | 101.0 dB/mW | 0.79 mW | +22 dB | Comfortable |
| Grado SR80x | 38 Ω | 98.0 dB/mW | 1.6 mW | +21 dB | Comfortable |
| Sennheiser HD 560S | 120 Ω | 100.8 dB/mW | 0.83 mW | +19 dB | Comfortable |
| HiFiMAN Edition XS | 18 Ω | 92.0 dB | 6.3 mW | +17 dB | Comfortable |
| HiFiMAN Arya Stealth | 32 Ω | 94.0 dB | 4.0 mW | +18 dB | Comfortable |
| Dan Clark Audio AEON 2 Closed | 13 Ω | 90.0 dB/mW | 10 mW | +15 dB | Comfortable |
| Audeze LCD-5 | 14 Ω | 90.0 dB/mW | 10 mW | +15 dB | Comfortable |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 102.0 dB/mW | 0.63 mW | +17 dB | Comfortable |
| HiFiMAN HE400se | 25 Ω | 91.0 dB | 7.9 mW | +15 dB | Comfortable |
| HiFiMAN Sundara | 32 Ω | 92.0 dB | 6.3 mW | +16 dB | Comfortable |
| Dan Clark Audio Stealth | 23 Ω | 90.0 dB/mW | 10 mW | +15 dB | Comfortable |
| Fostex T50RP MK3 | 50 Ω | 92.0 dB/mW | 6.3 mW | +14 dB | Comfortable |
| AKG K702 | 62 Ω | 92.9 dB/mW | 5.1 mW | +14 dB | Comfortable |
| ZMF Verite Closed | 300 Ω | 99.0 dB/mW | 1.3 mW | +14 dB | Comfortable |
| Sennheiser HD 650 | 300 Ω | 97.8 dB/mW | 1.7 mW | +13 dB | Comfortable |
| Sennheiser HD 800S | 300 Ω | 96.8 dB/mW | 2.1 mW | +12 dB | Comfortable |
| Beyerdynamic DT 770 Pro (250Ω) | 250 Ω | 96.0 dB | 2.5 mW | +11 dB | Comfortable |
| Audio-Technica ATH-R70X | 470 Ω | 98.0 dB/mW | 1.6 mW | +11 dB | Comfortable |
| ZMF Atrium | 300 Ω | 96.0 dB/mW | 2.5 mW | +11 dB | Comfortable |
| Abyss AB-1266 Phi TC | 50 Ω | 88.0 dB/mW | 16 mW | +10 dB | Enough |
| Sennheiser HD 600 | 300 Ω | 91.8 dB/mW | 6.6 mW | +7 dB | Enough |
| HiFiMAN Susvara | 60 Ω | 83.0 dB | 50 mW | +4 dB | Enough |
At 1.6 µV of output noise, here is where that noise lands in the five most revealing in-ears in the database.
This one hisses. With the most sensitive in-ears in the database its own noise lands around 25 dB SPL, which you will hear between tracks and in quiet passages.
| In-ear | Impedance | Sensitivity | Hiss level |
|---|---|---|---|
| Simgot EA500 | 16 Ω | 141.0 dB/V | 25 dB SPL |
| Tanchjim EA FORCE | 17 Ω | 137.7 dB/V | 22 dB SPL |
| Shure SE846 | 9 Ω | 134.5 dB/V | 19 dB SPL |
| Campfire Audio Clara | 13.3 Ω | 134.1 dB/V | 18 dB SPL |
| 64 Audio Fourte | 10 Ω | 134.0 dB/V | 18 dB SPL |
At 1Ω output impedance, the one-eighth rule says this source suits headphones of 8.0Ω and above. 15 of the 567 models here fall below that. Most of them are multi-driver in-ears, and the mismatch tilts the frequency response audibly rather than subtly.
| As published | FiiO JM21 |
|---|---|
| DAC | Dual CS43198 (CS43198 x2) |
| Processor | Qualcomm Snapdragon 680 |
| Operating system | Android 13 |
| Storage | 32 GB (22 GB usable) with 3 GB RAM, or 64 GB (52 GB usable) with 4 GB RAM; single microSD, theoretically up to 2 TB |
| Outputs | 3.5 mm headphone out, 4.4 mm balanced headphone out, line out shared on 3.5 mm + 4.4 mm, 3.5 mm coaxial (shared PO) |
| Bluetooth | Bluetooth 5.0; transmit AAC/SBC/aptX/aptX HD/LDAC/LHDC; receive SBC/AAC/LDAC |
| Wi-Fi | 2.4 GHz / 5 GHz, DLNA, AirPlay, Wi-Fi song transfer |
| Formats | Local decoding up to 384kHz/32bit, DSD256 (Native); USB audio 768kHz/32bit, DSD512 |
| Screen | 4.7-inch, 750 x 1334, bezel-less |
| Battery | 2400 mAh (3 GB + 32 GB) / 3100 mAh (4 GB + 64 GB) |
| Battery life | 3.5 mm: 12.5 h (3G+32G) / 16 h (4G+64G) |
| Weight | 156 g |
| Dimensions | About 120.7 x 68 x 13 mm |
Copied from the makers’ own pages: fiio.com/jm21_parameters, fiio.com/jm21. Battery life is the maker’s own test figure.
| Source | Type | Price | Into 300 Ω | Output impedance | Output noise |
|---|---|---|---|---|---|
| FiiO KA11 | USB dongle | $29 | 22 mW | 0.7 Ω | 1.7 µV |
| FiiO KA15 | USB dongle | $109 | 19 mW | 0.8 Ω | 1.7 µV |
| Schiit Magni Unity | desktop amplifier | $119 | 415 mW | 0.1 Ω | 1.59 µV |
Of the 280 sources here, 6 do everything the FiiO JM21 does as a headphone output: reach 100 dB on every headphone it reaches, stay inside the one-eighth rule wherever it does and stay under the audible-hiss threshold wherever it does. The cheapest of them is the FiiO KA11 at $29, against this one’s $199 — $170 less, and a USB dongle rather than a portable player.
This counts the headphone output only; inputs, converters, the volume control and the build are outside it.
$189 · 70 mW into 32Ω · output Ω not published
Compare →$209 · 195 mW into 32Ω · 0.6 Ω out
Compare →$180 · 125 mW into 32Ω · output Ω not published
Compare →$179 · 70 mW into 32Ω · output Ω not published
Compare →$179 · 825 mW into 32Ω · output Ω not published
Compare →$350 · 18 mW into 32Ω · 1.5 Ω out
Compare →Compared with its closest rivals: vs FiiO M11S · vs FiiO M15S · vs FiiO M17 · vs FiiO M21 · vs FiiO M23 · vs FiiO M27 · vs FiiO M33 R2R · vs Hidizs AP80 Pro Max · vs Hidizs AP80 Pro-X · vs Shanling M1 Plus · vs Surfans F28.