Short answer
Both are desktop DAC/amps, $176 against $199.
The FiiO K11 R2R reaches 100 dB on 567 of the 567 models here, the Fosi Audio K7 on 566.
| Specification | FiiO K11 R2R | Fosi Audio K7 |
|---|---|---|
| Power into 32Ω | 460 mW | 600 mW |
| Power into 150Ω | 99 mW | 128 mW |
| Power into 300Ω | 50 mW | 64 mW |
| Power into 600Ω | 25 mW | 32 mW |
| Output impedance | 1.0 Ω | not published |
| Output noise | 7.2 µV | 2.5 µV |
| Price | $176 | $199 |
| Headphones it reaches 100 dB on out of 567 | 567 | 566 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Balanced | FiiO K11 R2R | Fosi Audio K7 |
|---|---|---|
| Socket | 4.4mm | 4.4mm |
| Power into 32Ω | 1.3 W | 2.1 W |
| Power into 300Ω | 220 mW | 224 mW derived |
| Output impedance | 1.5 Ω | not published |
| Output noise | 14.1 µV | 6.5 µV |
| Headphones it reaches 100 dB on out of 567 | 567 | 567 |
Through the balanced sockets the two are level on the same test: each reaches 100 dB on 567 of the 567 models here. Derived figures are worked out from the loads the maker did publish.
| As published | FiiO K11 R2R | Fosi Audio K7 |
|---|---|---|
| DAC | FiiO-developed fully differential 24-bit R2R (discrete resistor arrays) | AK4493SEQ |
| Outputs | 6.35 mm SE, 4.4 mm balanced, RCA line out, coaxial out (RCA, USB mode only) | 4.4 mm balanced, 3.5 mm SE, RCA |
| Inputs | USB-C, optical, coaxial (RCA) | USB-C, optical, coaxial, Bluetooth, 3.5 mm microphone |
| Bluetooth | not published | Bluetooth 5.0; SBC, AAC, aptX, aptX HD, aptX LL |
| Formats | USB: 384 kHz/32-bit, DSD256 | USB: PCM 384 kHz/32-bit, DSD256 |
| Power supply | External 12 V / 2 A adapter | External DC 12 V / 2 A adapter |
| Gain | Low / Medium / High | not published |
| Weight | 420 g | not published |
| Dimensions | 147 × 133 × 32.3 mm (including feet) | not published |
Copied from the makers’ own pages: fiio.com/k11r2r_parameters, fosiaudio.com/pages/fosi-audio-k7-dac-amp. Battery life is the maker’s own test figure.
| Load | FiiO K11 R2R | Fosi Audio K7 |
|---|---|---|
| 32 Ω | Published | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Published | Derived |
| 600 Ω | Derived | Derived |
Both makers publish a power rating. FiiO K11 R2R publishes at 32 Ω and at 300 Ω; Fosi Audio K7 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 K11 R2R figure is the maker’s own. On those rows the derived number is the one to doubt first.
1 headphone reaches 100 dB on the FiiO K11 R2R but not on the Fosi Audio K7 — Symphonium Titan.
121 headphones stay below the audible-hiss threshold on the Fosi Audio K7 but cross it on the FiiO K11 R2R (64 Audio Aspire 1, 64 Audio Nio, 64 Audio Ocean, 118 more).
566 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 K11 R2R has +40 dB of headroom there against +36 dB. 3 dB is about 2.2 times the power, which matters for peaks rather than for how loud the music sits.
Hiss below about 20 dB SPL is inaudible in a quiet room.
| Headphone | Impedance | Needs | FiiO K11 R2R headroom | Fosi Audio K7 headroom | FiiO K11 R2R hiss | Fosi Audio K7 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +40 dB | +36 dB | 32 dB | 22 dB |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +20 dB | +16 dB | 12 dB | 2 dB |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +24 dB | +25 dB | 10 dB | 1 dB |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +20 dB | +21 dB | 5 dB | -4 dB |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +18 dB | +18 dB | 4 dB | -5 dB |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +13 dB | +14 dB | -2 dB | -11 dB |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +9 dB | +10 dB | -6 dB | -15 dB |
| HiFiMAN Susvara | 60 Ω | 50 mW | +7 dB | +8 dB | -8 dB | -17 dB |
The Fosi Audio K7 costs $23 more than the FiiO K11 R2R. Out of the 567 models here, that difference buys 121 more models kept below the audible-hiss threshold.
It does not run one way only: the cheaper FiiO K11 R2R drives one model to 100 dB that the Fosi Audio K7 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 K11 R2R and Fosi Audio K7.