Short answer
Both are audio interfaces, $2499 against $2799.
The RME ADI-2 Pro EX reaches 100 dB on 567 of the 567 models here, the RME Fireface UFX II on 564.
| Specification | RME ADI-2 Pro EX | RME Fireface UFX II |
|---|---|---|
| Power into 32Ω | 1.9 W | 200 mW |
| Power into 150Ω | 540 mW | 43 mW |
| Power into 300Ω | 370 mW | 21 mW |
| Power into 600Ω | 185 mW | 11 mW |
| Output impedance | 0.1 Ω | 2 Ω |
| Output noise | 2.18 µV | not published |
| Price | $2499 | $2799 |
| Headphones it reaches 100 dB on out of 567 | 567 | 564 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Balanced | RME ADI-2 Pro EX | RME Fireface UFX II |
|---|---|---|
| Socket | 2 x 6.3 mm TRS (RME 'Advanced Balanced' mode uses both unbalanced jacks as one balanced pair) | no separate rating |
| Power into 32Ω | 4.2 W | — |
| Power into 300Ω | 1.4 W | — |
| Output impedance | 0.2 Ω | — |
| Output noise | not published | — |
| Headphones it reaches 100 dB on out of 567 | 567 | — |
Only the RME ADI-2 Pro EX has a separate balanced rating from its maker; through it, it reaches 100 dB on 567 of the 567 models here. The RME Fireface UFX II may still have a balanced socket — its spec sheet simply gives no figure for one, so there is nothing to put beside it.
| Load | RME ADI-2 Pro EX | RME Fireface UFX II |
|---|---|---|
| 32 Ω | Published | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Published | Derived |
| 600 Ω | Derived | Derived |
Both makers publish a power rating. RME ADI-2 Pro EX publishes at 32 Ω and at 300 Ω; RME Fireface UFX II 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 RME ADI-2 Pro EX figure is the maker’s own. On those rows the derived number is the one to doubt first.
3 headphones reach 100 dB on the RME ADI-2 Pro EX but not on the RME Fireface UFX II — Moondrop PARA, Symphonium Crimson, Symphonium Titan.
89 headphones are left alone by the RME ADI-2 Pro EX under the one-eighth rule but coloured by the RME Fireface UFX II (64 Audio Aspire 1, 64 Audio Fourte, 64 Audio Nio, 86 more).
564 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: RME ADI-2 Pro EX has +25 dB of headroom there against +12 dB. 13 dB is about 21 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for RME Fireface UFX II because that maker publishes no output noise figure.
| Headphone | Impedance | Needs | RME ADI-2 Pro EX headroom | RME Fireface UFX II headroom | RME ADI-2 Pro EX hiss | RME Fireface UFX II hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +45 dB | +32 dB damping | 21 dB | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +25 dB | +12 dB damping | 1 dB | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +31 dB | +21 dB | -1 dB | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +28 dB | +16 dB | -5 dB | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +24 dB | +13 dB | -6 dB | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +22 dB | +9 dB | -12 dB | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +17 dB | +5 dB | -16 dB | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | +13 dB | +3 dB | -18 dB | not published |
The RME Fireface UFX II costs $300 more than the RME ADI-2 Pro EX, and on these three axes the money buys nothing: among the 567 models here there is not one that the RME Fireface UFX II handles and the RME ADI-2 Pro EX does not — not on power, not on the one-eighth rule, not on hiss. The traffic runs the other way: the cheaper RME ADI-2 Pro EX drives 3 models to 100 dB and leaves 89 alone under the one-eighth rule that the RME Fireface UFX II does not.
Only published figures count here; blank axes are counted separately.
Each in full: RME ADI-2 Pro EX and RME Fireface UFX II.