Both are audio interfaces, $1300 against $1749. 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 Audient iD48 reaches 100 dB on 566 of the 567 models here, the RME Fireface UCX II on 564.
| Specification | Audient iD48 | RME Fireface UCX II |
|---|---|---|
| Power into 32Ω | 528 mW | 210 mW |
| Power into 150Ω | 265 mW | 45 mW |
| Power into 300Ω | 168 mW | 22 mW |
| Power into 600Ω | 126 mW | 11 mW |
| Output impedance | 50 Ω | 1 Ω |
| Output noise | not published | not published |
| Price | $1300 | $1749 |
| Headphones it reaches 100 dB on out of 567 | 566 | 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.
2 headphones reach 100 dB on the Audient iD48 but not on the RME Fireface UCX II — Moondrop PARA, Symphonium Crimson.
546 headphones are left alone by the RME Fireface UCX II under the one-eighth rule but coloured by the Audient iD48 (64 Audio Aspire 1, 64 Audio Fourte, 64 Audio Ocean, 543 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.
Each has a page of its own with every power figure traced to what the maker published and a full headphone list: Audient iD48 and RME Fireface UCX II. Or put either against your own headphones in the source comparison tool.