Both are desktop DAC/amps, $1430 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 K19 | FiiO K9 Pro |
|---|---|---|
| Power into 32Ω | 2.3 W | 2.0 W |
| Power into 150Ω | 512 mW | 482 mW |
| Power into 300Ω | 270 mW | 278 mW |
| Power into 600Ω | 135 mW | 139 mW |
| Output impedance | 0.6 Ω | 1.0 Ω |
| Output noise | 3.5 µV | 2.0 µV |
| Price | $1430 | $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.
14 headphones are left alone by the FiiO K19 under the one-eighth rule but coloured by the FiiO K9 Pro (64 Audio Nio, 64 Audio Volur, Campfire Audio Andromeda 2023, 11 more).
20 headphones stay below the audible-hiss threshold on the FiiO K9 Pro but cross it on the FiiO K19 (AFUL Performer 8, Audio-Technica ATH-CKS1100, Campfire Audio Andromeda 10, 17 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 K19 and FiiO K9 Pro. Or put either against your own headphones in the source comparison tool.