Short answer
Both are dongles, $109 against $99.
The FiiO KA15 reaches 100 dB on 566 of the 567 models here, the FiiO KA5 on 565.
| Specification | FiiO KA15 | FiiO KA5 |
|---|---|---|
| Power into 32Ω | 180 mW | 122 mW |
| Power into 150Ω | 38 mW | 26 mW |
| Power into 300Ω | 19 mW | 14 mW |
| Power into 600Ω | 9.5 mW | 6.8 mW |
| Output impedance | 0.8 Ω | 0.3 Ω |
| Output noise | 1.7 µV | 1.6 µV |
| Price | $109 | $99 |
| Headphones it reaches 100 dB on out of 567 | 566 | 565 |
| Balanced | FiiO KA15 | FiiO KA5 |
|---|---|---|
| Socket | 4.4mm | 4.4mm |
| Power into 32Ω | 560 mW | 265 mW |
| Power into 300Ω | 78 mW | 54 mW |
| Output impedance | 1.2 Ω | 0.35 Ω |
| Output noise | 3.2 µV | 1.8 µV |
| Headphones it reaches 100 dB on out of 567 | 566 | 565 |
Through the balanced sockets the FiiO KA15 reaches 100 dB on 566 of the 567 models here and the FiiO KA5 on 565.
| As published | FiiO KA15 | FiiO KA5 |
|---|---|---|
| DAC | CS43198 x2 | CS43198 x2 |
| Outputs | 3.5 mm SE (shared with S/PDIF out), 4.4 mm balanced | 3.5 mm SE (shared with S/PDIF out), 4.4 mm balanced |
| Connection | USB-C | USB-C |
| Formats | PCM 768 kHz/32-bit, DSD64/128/256; coaxial 384 kHz/32-bit | PCM 768 kHz/32-bit, DSD64/128/256 |
| Weight | 21 g | 19 g |
| Dimensions | About 52 x 25 x 11 mm | About 56.3 x 22 x 12 mm |
Copied from the makers’ own pages: fiio.com/KA15_parameters, fiio.com/ka5_parameters. Battery life is the maker’s own test figure.
| Load | FiiO KA15 | FiiO KA5 |
|---|---|---|
| 32 Ω | Published | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Published | Published |
| 600 Ω | Derived | Derived |
Both makers publish a power rating. FiiO KA15 publishes at 32 Ω and at 300 Ω; FiiO KA5 at 32 Ω and at 300 Ω. The other rows are worked out from those.
The two publish at the same loads, which is the one case where the rows of this table can be read straight across.
1 headphone reaches 100 dB on the FiiO KA15 but not on the FiiO KA5 — Moondrop PARA.
12 headphones are left alone by the FiiO KA5 under the one-eighth rule but coloured by the FiiO KA15 (64 Audio Nio, 64 Audio Volur, Campfire Audio Andromeda 2023, 9 more).
565 of the 567 models here reach 100 dB on both.
Headroom is at a 100 dB SPL peak.
The widest gap on the list is the Campfire Audio Andromeda 2020: FiiO KA15 has +16 dB of headroom there against +13 dB. 3 dB is about 2.1 times the power, which matters for peaks rather than for how loud the music sits.
Hiss below about 20 dB SPL is inaudible in a quiet room.
| Headphone | Impedance | Needs | FiiO KA15 headroom | FiiO KA5 headroom | FiiO KA15 hiss | FiiO KA5 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +36 dB | +33 dB | 19 dB | 19 dB |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +16 dB | +13 dB | -1 dB | -1 dB |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +20 dB | +18 dB | -3 dB | -3 dB |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +16 dB | +14 dB | -7 dB | -8 dB |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +14 dB | +12 dB | -8 dB | -9 dB |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +9 dB | +7 dB | -14 dB | -15 dB |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +5 dB | +3 dB | -18 dB | -19 dB |
| HiFiMAN Susvara | 60 Ω | 50 mW | +3 dB | +1 dB | -20 dB | -21 dB |
The FiiO KA15 costs $10 more than the FiiO KA5. Out of the 567 models here, that difference buys 1 more model driven to 100 dB.
It does not run one way only: the cheaper FiiO KA5 leaves 12 models alone under the one-eighth rule that the FiiO KA15 does not, which is the part worth checking against your own headphones before paying the difference.
Only published figures count here; blank axes are counted separately.