Both are dongles, $99 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 FiiO KA5 reaches 100 dB on 565 of the 567 models here, the HiBy FC4 on 561.
| Specification | FiiO KA5 | HiBy FC4 |
|---|---|---|
| Power into 32Ω | 122 mW | 110 mW |
| Power into 150Ω | 26 mW | 23 mW |
| Power into 300Ω | 14 mW | 12 mW |
| Power into 600Ω | 6.8 mW | 5.9 mW |
| Output impedance | 0.3 Ω | not published |
| Output noise | 1.6 µV | 1.7 µV |
| Price | $99 | $99 |
| Headphones it reaches 100 dB on out of 567 | 565 | 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.
4 headphones reach 100 dB on the FiiO KA5 but not on the HiBy FC4 — Moondrop COSMO, Symphonium Crimson, Symphonium Helios, 1 more.
561 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 KA5 and HiBy FC4. Or put either against your own headphones in the source comparison tool.