Short answer
Both are portable players, $199 against $209.
The FiiO JM21 reaches 100 dB on 566 of the 567 models here, the Shanling M1 Plus on 564.
| Specification | FiiO JM21 | Shanling M1 Plus |
|---|---|---|
| Power into 32Ω | 245 mW | 195 mW |
| Power into 150Ω | 56 mW | 42 mW |
| Power into 300Ω | 30 mW | 21 mW |
| Power into 600Ω | 15 mW | 10 mW |
| Output impedance | 1 Ω | 0.6 Ω |
| Output noise | 1.6 µV | not published |
| Price | $199 | $209 |
| Headphones it reaches 100 dB on out of 567 | 566 | 564 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Balanced | FiiO JM21 | Shanling M1 Plus |
|---|---|---|
| Socket | 4.4mm | 4.4mm |
| Power into 32Ω | 700 mW | 660 mW |
| Power into 300Ω | 80 mW | 70 mW derived |
| Output impedance | 1.5 Ω | 1.2 Ω |
| Output noise | 1.7 µV | not published |
| Headphones it reaches 100 dB on out of 567 | 566 | 566 |
Through the balanced sockets the two are level on the same test: each reaches 100 dB on 566 of the 567 models here. Derived figures are worked out from the loads the maker did publish.
| As published | FiiO JM21 | Shanling M1 Plus |
|---|---|---|
| DAC | Dual CS43198 (CS43198 x2) | ESS ES9069Q |
| Processor | Qualcomm Snapdragon 680 | Ingenic X2000 |
| Operating system | Android 13 | MTouch (Shanling's own system) |
| 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 | microSD card slot (internal storage not stated) |
| 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) | 3.5 mm single-ended, 4.4 mm balanced, USB-C; 3.5 mm coaxial S/PDIF out |
| Bluetooth | Bluetooth 5.0; transmit AAC/SBC/aptX/aptX HD/LDAC/LHDC; receive SBC/AAC/LDAC | Bluetooth 5.2, bidirectional: LDAC, aptX HD, aptX, AAC |
| Wi-Fi | 2.4 GHz / 5 GHz, DLNA, AirPlay, Wi-Fi song transfer | 2.4 / 5 GHz, DLNA, AirPlay, OTA updates |
| Formats | Local decoding up to 384kHz/32bit, DSD256 (Native); USB audio 768kHz/32bit, DSD512 | PCM 32 bit / 768 kHz, DSD512 |
| Screen | 4.7-inch, 750 x 1334, bezel-less | 3.2-inch, 320 x 480, touchscreen |
| Battery | 2400 mAh (3 GB + 32 GB) / 3100 mAh (4 GB + 64 GB) | 2100 mAh |
| Battery life | 3.5 mm: 12.5 h (3G+32G) / 16 h (4G+64G) | Up to 12.5 h (no test condition given) |
| Weight | 156 g | 116 g |
| Dimensions | About 120.7 x 68 x 13 mm | 86 x 61 x 17 mm |
Copied from the makers’ own pages: fiio.com/jm21_parameters, fiio.com/jm21, en.shanling.com/article-IntroM1Plus.html. Battery life is the maker’s own test figure.
| Load | FiiO JM21 | Shanling M1 Plus |
|---|---|---|
| 32 Ω | Published | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Published | Derived |
| 600 Ω | Derived | Derived |
Both makers publish a power rating. FiiO JM21 publishes at 32 Ω and at 300 Ω; Shanling M1 Plus at 32 Ω. The other rows are worked out from those.
So the two columns are not equally firm row by row: at 300 Ω only the FiiO JM21 figure is the maker’s own. On those rows the derived number is the one to doubt first.
2 headphones reach 100 dB on the FiiO JM21 but not on the Shanling M1 Plus — Moondrop PARA, Symphonium Crimson.
14 headphones are left alone by the Shanling M1 Plus under the one-eighth rule but coloured by the FiiO JM21 (64 Audio Nio, 64 Audio Volur, Campfire Audio Andromeda 2023, 11 more).
564 of the 567 models here reach 100 dB on both.
Headroom is at a 100 dB SPL peak.
The widest gap on the list is the Shure SE846: FiiO JM21 has +37 dB of headroom there against +31 dB. 6 dB is about 3.7 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Shanling M1 Plus because that maker publishes no output noise figure.
| Headphone | Impedance | Needs | FiiO JM21 headroom | Shanling M1 Plus headroom | FiiO JM21 hiss | Shanling M1 Plus hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +37 dB | +31 dB | 19 dB | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +17 dB | +11 dB | -1 dB | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +22 dB | +21 dB | -3 dB | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +17 dB | +16 dB | -8 dB | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +15 dB | +13 dB | -9 dB | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +11 dB | +9 dB | -15 dB | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +7 dB | +5 dB | -19 dB | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | +4 dB | +3 dB | -21 dB | not published |
The Shanling M1 Plus costs $10 more than the FiiO JM21. Out of the 567 models here, that difference buys 14 more models left alone under the one-eighth rule.
It does not run one way only: the cheaper FiiO JM21 drives 2 models to 100 dB that the Shanling M1 Plus does not, which is the part worth checking against your own headphones before paying the difference.
Only published figures count here; blank axes are counted separately.
Each in full: FiiO JM21 and Shanling M1 Plus.