Short answer
Both are dongles, $109 against $69.
The FiiO KA15 reaches 100 dB on 566 of the 567 models here, the iBasso DC03 Pro on 560.
| Specification | FiiO KA15 | iBasso DC03 Pro |
|---|---|---|
| Power into 32Ω | 180 mW | 98 mW |
| Power into 150Ω | 38 mW | 21 mW |
| Power into 300Ω | 19 mW | 10 mW |
| Power into 600Ω | 9.5 mW | 5.2 mW |
| Output impedance | 0.8 Ω | 0.12 Ω |
| Output noise | 1.7 µV | 0.9 µV |
| Price | $109 | $69 |
| Headphones it reaches 100 dB on out of 567 | 566 | 560 |
| Balanced | FiiO KA15 | iBasso DC03 Pro |
|---|---|---|
| Socket | 4.4mm | no separate rating |
| Power into 32Ω | 560 mW | — |
| Power into 300Ω | 78 mW | — |
| Output impedance | 1.2 Ω | — |
| Output noise | 3.2 µV | — |
| Headphones it reaches 100 dB on out of 567 | 566 | — |
Only the FiiO KA15 has a separate balanced rating from its maker; through it, it reaches 100 dB on 566 of the 567 models here. The iBasso DC03 Pro may still have a balanced socket — its spec sheet simply gives no figure for one, so there is nothing to put beside it.
| Load | FiiO KA15 | iBasso DC03 Pro |
|---|---|---|
| 32 Ω | Published | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Published | Derived |
| 600 Ω | Derived | Derived |
Both makers publish a power rating. FiiO KA15 publishes at 32 Ω and at 300 Ω; iBasso DC03 Pro at 32 Ω. The other rows are worked out from those.
So the two columns are not equally firm row by row: at 300 Ω only the FiiO KA15 figure is the maker’s own. On those rows the derived number is the one to doubt first.
6 headphones reach 100 dB on the FiiO KA15 but not on the iBasso DC03 Pro — Moondrop COSMO, Moondrop PARA, Moondrop PARA 2, 3 more.
12 headphones are left alone by the iBasso DC03 Pro under the one-eighth rule but coloured by the FiiO KA15 (64 Audio Nio, 64 Audio Volur, Campfire Audio Andromeda 2023, 9 more).
1 headphone stays below the audible-hiss threshold on the iBasso DC03 Pro but crosses it on the FiiO KA15 (Tanchjim EA FORCE).
560 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 +28 dB. 8 dB is about 5.9 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 | iBasso DC03 Pro headroom | FiiO KA15 hiss | iBasso DC03 Pro hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +36 dB | +28 dB | 19 dB | 14 dB |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +16 dB | +8 dB | -1 dB | -6 dB |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +20 dB | +18 dB | -3 dB | -8 dB |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +16 dB | +13 dB | -7 dB | -13 dB |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +14 dB | +10 dB | -8 dB | -14 dB |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +9 dB | +6 dB | -14 dB | -20 dB |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +5 dB | +2 dB | -18 dB | -24 dB |
| HiFiMAN Susvara | 60 Ω | 50 mW | +3 dB | +0 dB | -20 dB | -26 dB |
The FiiO KA15 costs $40 more than the iBasso DC03 Pro. Out of the 567 models here, that difference buys 6 more models driven to 100 dB.
It does not run one way only: the cheaper iBasso DC03 Pro leaves 12 models alone under the one-eighth rule and keeps one below the audible-hiss threshold 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.
Each in full: FiiO KA15 and iBasso DC03 Pro.