Both are dongles, $79 against $109. 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 Hidizs S9 Pro reaches 100 dB on 560 of the 567 models here, the FiiO KA13 on 555.
| Specification | FiiO KA13 | Hidizs S9 Pro |
|---|---|---|
| Power into 32Ω | 50 mW | 100 mW |
| Power into 150Ω | 10 mW | 21 mW |
| Power into 300Ω | 5.0 mW | 11 mW |
| Power into 600Ω | 2.5 mW | 5.3 mW |
| Output impedance | 1.7 Ω | 0.3 Ω unverified |
| Output noise | 2.5 µV | 4 µV unverified |
| Price | $79 | $109 |
| Headphones it reaches 100 dB on out of 567 | 555 | 560 |
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.
| Load | FiiO KA13 | Hidizs S9 Pro |
|---|---|---|
| 32 Ω | Published | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Published | Derived |
| 600 Ω | Derived | Derived |
Both makers publish a power rating, which is less common than the table above makes it look: of the 280 sources here, 209 publish a figure at at least one load and only 2 publish one at all four. FiiO KA13 publishes at 32 Ω and at 300 Ω; Hidizs S9 Pro at 32 Ω. Every other row is worked out from those — between two published loads, or beyond them holding voltage constant, which understates rather than flatters.
So the two columns are not equally firm row by row: at 300 Ω only the FiiO KA13 figure is the maker’s own. On those rows the derived number is the one to doubt first.
What each of these labels means, and why a derived figure is still worth printing, is set out in how this data was built.
2 headphones reach 100 dB on the FiiO KA13 but not on the Hidizs S9 Pro — Moondrop PARA 2, Symphonium Zenith.
7 headphones reach 100 dB on the Hidizs S9 Pro but not on the FiiO KA13 — Beyerdynamic DT 880 Edition (600Ω), Beyerdynamic DT 990 Edition (600Ω), HiFiMAN HE-6se V2, 4 more.
553 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.
The counts above say how many models the two treat differently. This says by how much. The same 8 headphones appear on every page of this kind, ordered from the easiest to drive to the hardest, so a row can be read across pages as well as across columns. Headroom is at a 100 dB SPL peak.
The widest gap on the list is the Sennheiser HD 600: Hidizs S9 Pro has +2 dB of headroom there against -1 dB. 3 dB is about 2.1 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Hidizs S9 Pro because that maker publishes no output noise figure. That is a gap in the specification, not a quiet amplifier, and it is left blank here rather than filled with a plausible number.
| Headphone | Impedance | Needs | FiiO KA13 headroom | Hidizs S9 Pro headroom | FiiO KA13 hiss | Hidizs S9 Pro hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +30 dB damping | +28 dB | 22 dB | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +10 dB damping | +8 dB | 2 dB | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +15 dB | +18 dB | 1 dB | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +10 dB | +13 dB | -4 dB | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +8 dB | +10 dB | -5 dB | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +3 dB | +6 dB | -11 dB | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | -1 dB | +2 dB | -15 dB | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | -3 dB | +0 dB | -17 dB | not published |
The Hidizs S9 Pro costs $30 more than the FiiO KA13. Out of the 567 models here, that difference buys 7 more models driven to 100 dB.
It does not run one way only: the cheaper FiiO KA13 drives 2 models to 100 dB that the Hidizs S9 Pro does not, which is the part worth checking against your own headphones before paying the difference.
Everything in this paragraph counts only figures the two makers published. An advantage on an axis one of them leaves blank cannot be counted, and is not counted — how often that happens is its own page.
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 Hidizs S9 Pro. Or put either against your own headphones in the source comparison tool.