Short answer
Both are desktop DAC/amps, $1430 against $1499.
On raw power they are level: each reaches 100 dB on 567 of the 567 non-electrostatic models here.
| Specification | FiiO K19 | Matrix mini-i Pro 4 |
|---|---|---|
| Power into 32Ω | 2.3 W | 1.2 W |
| Power into 150Ω | 512 mW | 366 mW |
| Power into 300Ω | 270 mW | 260 mW |
| Power into 600Ω | 135 mW | 130 mW |
| Output impedance | 0.6 Ω | 11 Ω |
| Output noise | 3.5 µV | not published |
| Price | $1430 | $1499 |
| Headphones it reaches 100 dB on out of 567 | 567 | 567 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Balanced | FiiO K19 | Matrix mini-i Pro 4 |
|---|---|---|
| Socket | 4.4mm / XLR4 | 4.4mm |
| Power into 32Ω | 8.0 W | 2.1 W derived |
| Power into 300Ω | 1.1 W | 950 mW |
| Output impedance | 0.6 Ω | 22 Ω |
| Output noise | 6.0 µV | not published |
| Headphones it reaches 100 dB on out of 567 | 567 | 567 |
Through the balanced sockets the two are level on the same test: each reaches 100 dB on 567 of the 567 models here. Derived figures are worked out from the loads the maker did publish.
| Load | FiiO K19 | Matrix mini-i Pro 4 |
|---|---|---|
| 32 Ω | Published | Derived |
| 150 Ω | Derived | Derived |
| 300 Ω | Published | Published |
| 600 Ω | Derived | Published |
Both makers publish a power rating. FiiO K19 publishes at 32 Ω and at 300 Ω; Matrix mini-i Pro 4 at 300 Ω and at 600 Ω. The other rows are worked out from those.
So the two columns are not equally firm row by row: at 32 Ω only the FiiO K19 figure is the maker’s own and at 600 Ω only the Matrix mini-i Pro 4 figure is the maker’s own. On those rows the derived number is the one to doubt first.
On power they are interchangeable across this whole database: there is no headphone here that one reaches 100 dB on and the other does not.
519 headphones are left alone by the FiiO K19 under the one-eighth rule but coloured by the Matrix mini-i Pro 4 (64 Audio Aspire 1, 64 Audio Fourte, 64 Audio Nio, 516 more).
567 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 K19 has +28 dB of headroom there against +19 dB. 8 dB is about 6.9 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Matrix mini-i Pro 4 because that maker publishes no output noise figure.
| Headphone | Impedance | Needs | FiiO K19 headroom | Matrix mini-i Pro 4 headroom | FiiO K19 hiss | Matrix mini-i Pro 4 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +48 dB | +39 dB damping | 25 dB | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +28 dB | +19 dB damping | 5 dB | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +31 dB | +29 dB damping | 3 dB | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +27 dB | +26 dB | -1 dB | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +25 dB | +21 dB damping | -2 dB | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +20 dB | +20 dB | -8 dB | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +16 dB | +16 dB | -12 dB | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | +14 dB | +12 dB damping | -14 dB | not published |
The Matrix mini-i Pro 4 costs $69 more than the FiiO K19, and on these three axes the money buys nothing: among the 567 models here there is not one that the Matrix mini-i Pro 4 handles and the FiiO K19 does not — not on power, not on the one-eighth rule, not on hiss. The traffic runs the other way: the cheaper FiiO K19 leaves 519 models alone under the one-eighth rule that the Matrix mini-i Pro 4 does not.
Only published figures count here; blank axes are counted separately.
Each in full: FiiO K19 and Matrix mini-i Pro 4.