Short answer
Both are desktop DAC/amps, $2050 against $1499.
The Matrix mini-i Pro 4 reaches 100 dB on 567 of the 567 models here, the Ferrum ERCO on 566.
| Specification | Ferrum ERCO | Matrix mini-i Pro 4 |
|---|---|---|
| Power into 32Ω | 1.1 W | 1.2 W |
| Power into 150Ω | 580 mW | 366 mW |
| Power into 300Ω | 300 mW | 260 mW |
| Power into 600Ω | 150 mW | 130 mW |
| Output impedance | 0.3 Ω | 11 Ω |
| Output noise | not published | not published |
| Price | $2050 | $1499 |
| Headphones it reaches 100 dB on out of 567 | 566 | 567 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Balanced | Ferrum ERCO | Matrix mini-i Pro 4 |
|---|---|---|
| Socket | 4-pin XLR | 4.4mm |
| Power into 32Ω | 3.9 W derived | 2.1 W derived |
| Power into 300Ω | 1.2 W | 950 mW |
| Output impedance | 0.3 Ω | 22 Ω |
| Output noise | not published | 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 | Ferrum ERCO | Matrix mini-i Pro 4 |
|---|---|---|
| 32 Ω | Derived | Derived |
| 150 Ω | Derived | Derived |
| 300 Ω | Published | Published |
| 600 Ω | Derived | Published |
Both makers publish a power rating. Ferrum ERCO publishes 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 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.
1 headphone reaches 100 dB on the Matrix mini-i Pro 4 but not on the Ferrum ERCO — Symphonium Titan.
520 headphones are left alone by the Ferrum ERCO under the one-eighth rule but coloured by the Matrix mini-i Pro 4 (64 Audio Aspire 1, 64 Audio Fourte, 64 Audio Nio, 517 more).
566 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 HiFiMAN Susvara: Ferrum ERCO has +15 dB of headroom there against +12 dB. 3 dB is twice the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Ferrum ERCO and Matrix mini-i Pro 4 because neither maker publishes no output noise figure.
| Headphone | Impedance | Needs | Ferrum ERCO headroom | Matrix mini-i Pro 4 headroom | Ferrum ERCO hiss | Matrix mini-i Pro 4 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +39 dB | +39 dB damping | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +19 dB | +19 dB damping | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +32 dB | +29 dB damping | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +28 dB | +26 dB | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +20 dB | +21 dB damping | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +21 dB | +20 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +17 dB | +16 dB | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | +15 dB | +12 dB damping | not published | not published |
The Ferrum ERCO costs $551 more than the Matrix mini-i Pro 4. Out of the 567 models here, that difference buys 520 more models left alone under the one-eighth rule.
It does not run one way only: the cheaper Matrix mini-i Pro 4 drives one model to 100 dB that the Ferrum ERCO 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: Ferrum ERCO and Matrix mini-i Pro 4.