Both are dongles, $79 against $99. 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?
The HiBy FC4 reaches 100 dB on 561 of the 567 models here, the FiiO KA13 on 555.
| Specification | FiiO KA13 | HiBy FC4 |
|---|---|---|
| Power into 32Ω | 50 mW | 110 mW |
| Power into 150Ω | 10 mW | 23 mW |
| Power into 300Ω | 5.0 mW | 12 mW |
| Power into 600Ω | 2.5 mW | 5.9 mW |
| Output impedance | 1.7 Ω | not published |
| Output noise | 2.5 µV | 1.7 µV |
| Price | $79 | $99 |
| Headphones it reaches 100 dB on out of 567 | 555 | 561 |
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.
1 headphone reaches 100 dB on the FiiO KA13 but not on the HiBy FC4 — Symphonium Zenith.
7 headphones reach 100 dB on the HiBy FC4 but not on the FiiO KA13 — Beyerdynamic DT 880 Edition (600Ω), Beyerdynamic DT 990 Edition (600Ω), HiFiMAN HE-6se V2, 4 more.
8 headphones stay below the audible-hiss threshold on the HiBy FC4 but cross it on the FiiO KA13 (64 Audio Fourte, Campfire Audio Andromeda 10, Campfire Audio Andromeda 2023, 5 more).
554 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 KA13 and HiBy FC4. Or put either against your own headphones in the source comparison tool.