Both are desktop DAC/amps, $990 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 K17 | FiiO K9 Pro |
|---|---|---|
| Power into 32Ω | 1.9 W | 2.0 W |
| Power into 150Ω | 431 mW | 482 mW |
| Power into 300Ω | 240 mW | 278 mW |
| Power into 600Ω | 120 mW | 139 mW |
| Output impedance | 1.0 Ω | 1.0 Ω |
| Output noise | 5.0 µV | 2.0 µV |
| Price | $990 | $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.
55 headphones stay below the audible-hiss threshold on the FiiO K9 Pro but cross it on the FiiO K17 (64 Audio Nio, 64 Audio U12t, 64 Audio U18s, 52 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 K17 and FiiO K9 Pro. Or put either against your own headphones in the source comparison tool.