Both are desktop DAC/amps, $143 against $799. This page puts them side by side on the only three things a maker can be held to — power, output impedance and noise — and then asks the question that actually matters: which headphones do they treat differently?
On raw power they are level: each reaches 100 dB on 567 of the 567 non-electrostatic models here.
| Specification | FiiO K11 | FiiO K9 Pro |
|---|---|---|
| Power into 32Ω | 520 mW | 2.0 W |
| Power into 150Ω | 115 mW | 482 mW |
| Power into 300Ω | 60 mW | 278 mW |
| Power into 600Ω | 30 mW | 139 mW |
| Output impedance | 1.2 Ω | 1.0 Ω |
| Output noise | 2.8 µV | 2.0 µV |
| Price | $143 | $799 |
| Headphones it reaches 100 dB on out of 567 | 567 | 567 |
A figure marked not published is missing from the maker’s own material, which is not the same as being good or bad. Where one of these two publishes a number and the other does not, the comparison on that axis cannot be made at all — and saying so is more useful than guessing.
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 K9 Pro under the one-eighth rule but coloured by the FiiO K11 (64 Audio Ocean, 64 Audio U18s, 64 Audio U6t, 20 more).
10 headphones stay below the audible-hiss threshold on the FiiO K9 Pro but cross it on the FiiO K11 (Campfire Audio Andromeda 10, Campfire Audio Andromeda 2023, Grado Signature HP100 SE, 7 more).
567 of the 567 models here reach 100 dB on both. That is a power count and nothing more; whether either source suits a given headphone also depends on the two lines above.
Each has a page of its own with every power figure traced to what the maker published and a full headphone list: FiiO K11 and FiiO K9 Pro. Or put either against your own headphones in the source comparison tool.