Short answer
Both are dongles, $79 against $109.
The FiiO KA15 reaches 100 dB on 566 of the 567 models here, the FiiO KA13 on 555.
| Specification | FiiO KA13 | FiiO KA15 |
|---|---|---|
| Power into 32Ω | 50 mW | 180 mW |
| Power into 150Ω | 10 mW | 38 mW |
| Power into 300Ω | 5.0 mW | 19 mW |
| Power into 600Ω | 2.5 mW | 9.5 mW |
| Output impedance | 1.7 Ω | 0.8 Ω |
| Output noise | 2.5 µV | 1.7 µV |
| Price | $79 | $109 |
| Headphones it reaches 100 dB on out of 567 | 555 | 566 |
| Balanced | FiiO KA13 | FiiO KA15 |
|---|---|---|
| Socket | 4.4mm | 4.4mm |
| Power into 32Ω | 260 mW | 560 mW |
| Power into 300Ω | 20 mW | 78 mW |
| Output impedance | 1.8 Ω | 1.2 Ω |
| Output noise | 4.6 µV | 3.2 µV |
| Headphones it reaches 100 dB on out of 567 | 565 | 566 |
Through the balanced sockets the FiiO KA15 reaches 100 dB on 566 of the 567 models here and the FiiO KA13 on 565.
| As published | FiiO KA13 | FiiO KA15 |
|---|---|---|
| DAC | CS43131 x2 | CS43198 x2 |
| Outputs | 3.5 mm SE (shared with S/PDIF coaxial 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 384 kHz/32-bit, DSD64/128/256; coaxial 384 kHz/32-bit | PCM 768 kHz/32-bit, DSD64/128/256; coaxial 384 kHz/32-bit |
| Weight | 19 g | 21 g |
| Dimensions | About 56.5 x 22 x 10.5 mm | About 52 x 25 x 11 mm |
Copied from the makers’ own pages: fiio.com/ka13_parameters, fiio.com/KA15_parameters. Battery life is the maker’s own test figure.
| Load | FiiO KA13 | FiiO KA15 |
|---|---|---|
| 32 Ω | Published | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Published | Published |
| 600 Ω | Derived | Derived |
Both makers publish a power rating. FiiO KA13 publishes at 32 Ω and at 300 Ω; FiiO KA15 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.
11 headphones reach 100 dB on the FiiO KA15 but not on the FiiO KA13 — Beyerdynamic DT 880 Edition (600Ω), Beyerdynamic DT 990 Edition (600Ω), HiFiMAN HE-6se V2, 8 more.
55 headphones are left alone by the FiiO KA15 under the one-eighth rule but coloured by the FiiO KA13 (64 Audio Aspire 1, 64 Audio Fourte, 64 Audio Ocean, 52 more).
8 headphones stay below the audible-hiss threshold on the FiiO KA15 but cross it on the FiiO KA13 (64 Audio Fourte, Campfire Audio Andromeda 10, Campfire Audio Andromeda 2023, 5 more).
555 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 Shure SE846: FiiO KA15 has +36 dB of headroom there against +30 dB. 6 dB is about 4.1 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 KA13 headroom | FiiO KA15 headroom | FiiO KA13 hiss | FiiO KA15 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +30 dB damping | +36 dB | 22 dB | 19 dB |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +10 dB damping | +16 dB | 2 dB | -1 dB |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +15 dB | +20 dB | 1 dB | -3 dB |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +10 dB | +16 dB | -4 dB | -7 dB |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +8 dB | +14 dB | -5 dB | -8 dB |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +3 dB | +9 dB | -11 dB | -14 dB |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | -1 dB | +5 dB | -15 dB | -18 dB |
| HiFiMAN Susvara | 60 Ω | 50 mW | -3 dB | +3 dB | -17 dB | -20 dB |
The FiiO KA15 costs $30 more than the FiiO KA13. Out of the 567 models here, that difference buys 11 more models driven to 100 dB, 55 more models left alone under the one-eighth rule and 8 more models kept below the audible-hiss threshold.
Nothing runs the other way: there is no axis here on which the cheaper of the two does better.
Only published figures count here; blank axes are counted separately.