Short answer
Both are desktop DAC/amps, $2050 against $2499.
The RME ADI-2/4 Pro SE reaches 100 dB on 567 of the 567 models here, the Ferrum ERCO on 566.
| Specification | Ferrum ERCO | RME ADI-2/4 Pro SE |
|---|---|---|
| Power into 32Ω | 1.1 W | 1.9 W |
| Power into 150Ω | 580 mW | 405 mW |
| Power into 300Ω | 300 mW | 203 mW |
| Power into 600Ω | 150 mW | 101 mW |
| Output impedance | 0.3 Ω | 0.1 Ω |
| Output noise | not published | 1.09 µV |
| Price | $2050 | $2499 |
| 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 | RME ADI-2/4 Pro SE |
|---|---|---|
| Socket | 4-pin XLR | 4.4mm Pentaconn |
| Power into 32Ω | 3.9 W derived | 10.6 W derived |
| Power into 300Ω | 1.2 W | 1.1 W derived |
| Output impedance | 0.3 Ω | 0.2 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 | RME ADI-2/4 Pro SE |
|---|---|---|
| 32 Ω | Derived | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Published | Derived |
| 600 Ω | Derived | Derived |
Both makers publish a power rating. Ferrum ERCO publishes at 300 Ω; RME ADI-2/4 Pro SE 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 Ferrum ERCO figure is the maker’s own and at 32 Ω only the RME ADI-2/4 Pro SE 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 RME ADI-2/4 Pro SE but not on the Ferrum ERCO — Symphonium Titan.
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 Shure SE846: RME ADI-2/4 Pro SE has +41 dB of headroom there against +39 dB. 2 dB is about 1.7 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Ferrum ERCO because that maker publishes no output noise figure.
| Headphone | Impedance | Needs | Ferrum ERCO headroom | RME ADI-2/4 Pro SE headroom | Ferrum ERCO hiss | RME ADI-2/4 Pro SE hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +39 dB | +41 dB | not published | 15 dB |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +19 dB | +21 dB | not published | -5 dB |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +32 dB | +30 dB | not published | -7 dB |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +28 dB | +26 dB | not published | -11 dB |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +20 dB | +23 dB | not published | -12 dB |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +21 dB | +19 dB | not published | -18 dB |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +17 dB | +15 dB | not published | -22 dB |
| HiFiMAN Susvara | 60 Ω | 50 mW | +15 dB | +13 dB | not published | -24 dB |
The RME ADI-2/4 Pro SE costs $449 more than the Ferrum ERCO. Out of the 567 models here, that difference buys 1 more model driven to 100 dB.
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.
Each in full: Ferrum ERCO and RME ADI-2/4 Pro SE.