Both are audio interfaces, $2199 against $2799. This page puts them side by side on the only three things a maker can be held to — power, output impedance and noise — and then asks the question that actually matters: which headphones do they treat differently?
The RME ADI-2 Pro FS R reaches 100 dB on 567 of the 567 models here, the RME Fireface UFX II on 564.
| Specification | RME ADI-2 Pro FS R | RME Fireface UFX II |
|---|---|---|
| Power into 32Ω | 3.0 W | 200 mW |
| Power into 150Ω | 634 mW | 43 mW |
| Power into 300Ω | 317 mW | 21 mW |
| Power into 600Ω | 158 mW | 11 mW |
| Output impedance | 0.1 Ω | 2 Ω |
| Output noise | 2.18 µV | not published |
| Price | $2199 | $2799 |
| Headphones it reaches 100 dB on out of 567 | 567 | 564 |
A figure marked not published is missing from the maker’s own material, which is not the same as being good or bad. Where one of these two publishes a number and the other does not, the comparison on that axis cannot be made at all — and saying so is more useful than guessing.
| Load | RME ADI-2 Pro FS R | RME Fireface UFX II |
|---|---|---|
| 32 Ω | Upper bound | Published |
| 150 Ω | Upper bound | Derived |
| 300 Ω | Upper bound | Derived |
| 600 Ω | Upper bound | Derived |
These two columns are not the same kind of number, and that matters more than the gap between them. RME Fireface UFX II publishes a power rating (at 32 Ω); RME ADI-2 Pro FS R publishes no power figure at any load, only a maximum output voltage, so every milliwatt in its column is a ceiling worked out from that voltage.
A ceiling assumes the amplifier holds that voltage into the load, and nothing on RME ADI-2 Pro FS R’s own sheet says it does. It is the most flattering reading available, and it is used here only because the alternative is a blank. Where the RME ADI-2 Pro FS R column looks the stronger of the two, treat the difference as unproven rather than measured. 24 of the 280 sources here are in that position, with no published power rating at any load.
What each of these labels means, and why a derived figure is still worth printing, is set out in how this data was built.
3 headphones reach 100 dB on the RME ADI-2 Pro FS R 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 FS R 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. That is a power count and nothing more; whether either source suits a given headphone also depends on the two lines above.
The counts above say how many models the two treat differently. This says by how much. The same 8 headphones appear on every page of this kind, ordered from the easiest to drive to the hardest, so a row can be read across pages as well as across columns. Headroom is at a 100 dB SPL peak.
The widest gap on the list is the Sennheiser HD 600: RME ADI-2 Pro FS R has +17 dB of headroom there against +5 dB. 12 dB is about 15 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. That is a gap in the specification, not a quiet amplifier, and it is left blank here rather than filled with a plausible number.
| Headphone | Impedance | Needs | RME ADI-2 Pro FS R headroom | RME Fireface UFX II headroom | RME ADI-2 Pro FS R hiss | RME Fireface UFX II hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +43 dB | +32 dB damping | 21 dB | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +23 dB | +12 dB damping | 1 dB | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +32 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 | +25 dB | +13 dB | -6 dB | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +21 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 | +15 dB | +3 dB | -18 dB | not published |
The RME Fireface UFX II costs $600 more than the RME ADI-2 Pro FS R, 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 FS R 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 FS R drives 3 models to 100 dB and leaves 89 alone under the one-eighth rule that the RME Fireface UFX II does not.
Everything in this paragraph counts only figures the two makers published. An advantage on an axis one of them leaves blank cannot be counted, and is not counted — how often that happens is its own page.
Each has a page of its own with every power figure traced to what the maker published and a full headphone list: RME ADI-2 Pro FS R and RME Fireface UFX II. Or put either against your own headphones in the source comparison tool.