Short answer
Both are desktop DAC/amps, $143 against $176.
On raw power they are level: each reaches 100 dB on 567 of the 567 non-electrostatic models here.
| Specification | FiiO K11 | FiiO K11 R2R |
|---|---|---|
| Power into 32Ω | 520 mW | 460 mW |
| Power into 150Ω | 115 mW | 99 mW |
| Power into 300Ω | 60 mW | 50 mW |
| Power into 600Ω | 30 mW | 25 mW |
| Output impedance | 1.2 Ω | 1.0 Ω |
| Output noise | 2.8 µV | 7.2 µV |
| Price | $143 | $176 |
| Headphones it reaches 100 dB on out of 567 | 567 | 567 |
| Balanced | FiiO K11 | FiiO K11 R2R |
|---|---|---|
| Socket | 4.4mm | 4.4mm |
| Power into 32Ω | 1.4 W | 1.3 W |
| Power into 300Ω | 250 mW | 220 mW |
| Output impedance | 2.4 Ω | 1.5 Ω |
| Output noise | 4.9 µV | 14.1 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.
| As published | FiiO K11 | FiiO K11 R2R |
|---|---|---|
| DAC | CS43198 | FiiO-developed fully differential 24-bit R2R (discrete resistor arrays) |
| Outputs | 6.35 mm SE, 4.4 mm balanced, RCA line out, coaxial out (RCA, USB mode only) | 6.35 mm SE, 4.4 mm balanced, RCA line out, coaxial out (RCA, USB mode only) |
| Inputs | USB-C, optical, coaxial (RCA) | USB-C, optical, coaxial (RCA) |
| Formats | USB: PCM 384 kHz/32-bit, DSD256 native | USB: 384 kHz/32-bit, DSD256 |
| Power supply | External 12 V / 2 A adapter | External 12 V / 2 A adapter |
| Gain | Low / Medium / High | Low / Medium / High |
| Weight | 407 g | 420 g |
| Dimensions | 147 × 133 × 32.3 mm (including feet) | 147 × 133 × 32.3 mm (including feet) |
Copied from the makers’ own pages: fiio.com/k11_parameters, fiio.com/k11, fiio.com/k11r2r_parameters. Battery life is the maker’s own test figure.
| Load | FiiO K11 | FiiO K11 R2R |
|---|---|---|
| 32 Ω | Published | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Published | Published |
| 600 Ω | Derived | Derived |
Both makers publish a power rating. FiiO K11 publishes at 32 Ω and at 300 Ω; FiiO K11 R2R at 32 Ω and at 300 Ω. The other rows are worked out from those.
The two publish at the same loads, which is the one case where the rows of this table can be read straight across.
On power they are interchangeable across this whole database: there is no headphone here that one reaches 100 dB on and the other does not.
23 headphones are left alone by the FiiO K11 R2R under the one-eighth rule but coloured by the FiiO K11 (64 Audio Ocean, 64 Audio U18s, 64 Audio U6t, 20 more).
115 headphones stay below the audible-hiss threshold on the FiiO K11 but cross it on the FiiO K11 R2R (64 Audio Aspire 1, 64 Audio Nio, 64 Audio Ocean, 112 more).
567 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 Sennheiser HD 600: FiiO K11 has +10 dB of headroom there against +9 dB. 1 dB is about 1.2 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 headroom | FiiO K11 R2R headroom | FiiO K11 hiss | FiiO K11 R2R hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +40 dB damping | +40 dB | 23 dB | 32 dB |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +20 dB damping | +20 dB | 3 dB | 12 dB |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +25 dB | +24 dB | 1 dB | 10 dB |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +21 dB | +20 dB | -3 dB | 5 dB |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +19 dB | +18 dB | -4 dB | 4 dB |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +14 dB | +13 dB | -10 dB | -2 dB |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +10 dB | +9 dB | -14 dB | -6 dB |
| HiFiMAN Susvara | 60 Ω | 50 mW | +7 dB | +7 dB | -16 dB | -8 dB |
The FiiO K11 R2R costs $33 more than the FiiO K11. Out of the 567 models here, that difference buys 23 more models left alone under the one-eighth rule.
It does not run one way only: the cheaper FiiO K11 keeps 115 models below the audible-hiss threshold that the FiiO K11 R2R 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 and FiiO K11 R2R.