The RME Fireface UCX II is an audio interface at $1749. It delivers 210 mW into 32Ω and 22 mW into 300Ω, which ranks it 156 of 280 for raw power among the sources in this database.
Measured at 100 dB SPL it has comfortable headroom on 531 of the 567 dynamic and planar headphones catalogued here, enough but not generous on 30, only marginal on 3 and not enough power for 3. Power is published at 32Ω; the rest of the table is derived from those figures. Output noise is not published, so the hiss estimate cannot be run.
The manufacturer publishes 210 mW into 32Ω. The rest of the table is worked out from those.
Derived rows hold output voltage steady, as an amplifier does (method).
Source: rme-audio.de.
| Load | Power | Status | How it was arrived at |
|---|---|---|---|
| 32 Ω | 210 mW | Published | the manufacturer publishes this figure at this exact load |
| 150 Ω | 45 mW | Derived | beyond the published loads, holding output voltage constant — which understates rather than flatters |
| 300 Ω | 22 mW | Derived | beyond the published loads, holding output voltage constant — which understates rather than flatters |
| 600 Ω | 11 mW | Derived | beyond the published loads, holding output voltage constant — which understates rather than flatters |
Easiest to hardest to drive, with headroom at a 100 dB SPL peak.
| Headphone | Impedance | Sensitivity | Needs | Headroom | Verdict |
|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 114.0 dB/mW | 0.04 mW | +32 dB | Comfortable |
| 64 Audio U12t | 12.6 Ω | 108.0 dB/mW | 0.16 mW | +27 dB | Comfortable |
| Shure SE215 | 17 Ω | 107.0 dB/mW | 0.20 mW | +27 dB | Comfortable |
| Moondrop Aria | 32 Ω | 107.1 dB/mW | 0.19 mW | +30 dB | Comfortable |
| Audeze LCD-X 2021 | 20 Ω | 103.0 dB/mW | 0.50 mW | +24 dB | Comfortable |
| Truthear Hexa | 20.5 Ω | 103.1 dB/mW | 0.49 mW | +24 dB | Comfortable |
| Sennheiser IE 200 | 18 Ω | 101.6 dB/mW | 0.69 mW | +22 dB | Comfortable |
| Sony MDR-7506 | 63 Ω | 106.0 dB/mW | 0.25 mW | +26 dB | Comfortable |
| Meze 99 Classics | 32 Ω | 103.0 dB/mW | 0.50 mW | +26 dB | Comfortable |
| Focal Clear MG | 55 Ω | 104.0 dB/mW | 0.40 mW | +25 dB | Comfortable |
| Philips SHP9500 | 32 Ω | 101.0 dB | 0.79 mW | +24 dB | Comfortable |
| Focal Utopia | 80 Ω | 104.0 dB/mW | 0.40 mW | +23 dB | Comfortable |
| Meze Empyrean | 32 Ω | 100.0 dB | 1.0 mW | +23 dB | Comfortable |
| Campfire Audio Andromeda 2020 | 9 Ω | 94.0 dB | 4.0 mW | +12 dB | Comfortable |
| Etymotic ER2SE | 15 Ω | 96.0 dB/mW | 2.5 mW | +16 dB | Comfortable |
| AKG K371 | 32 Ω | 99.1 dB/mW | 1.2 mW | +22 dB | Comfortable |
| Audio-Technica ATH-M50X | 38 Ω | 99.0 dB/mW | 1.3 mW | +21 dB | Comfortable |
| Beyerdynamic DT 900 Pro X | 48 Ω | 100.0 dB/mW | 1.0 mW | +21 dB | Comfortable |
| Audeze LCD-2 Classic | 70 Ω | 101.0 dB/mW | 0.79 mW | +21 dB | Comfortable |
| Grado SR80x | 38 Ω | 98.0 dB/mW | 1.6 mW | +20 dB | Comfortable |
| Sennheiser HD 560S | 120 Ω | 100.8 dB/mW | 0.83 mW | +18 dB | Comfortable |
| HiFiMAN Edition XS | 18 Ω | 92.0 dB | 6.3 mW | +13 dB | Comfortable |
| HiFiMAN Arya Stealth | 32 Ω | 94.0 dB | 4.0 mW | +17 dB | Comfortable |
| Dan Clark Audio AEON 2 Closed | 13 Ω | 90.0 dB/mW | 10 mW | +9 dB | Enough |
| Audeze LCD-5 | 14 Ω | 90.0 dB/mW | 10 mW | +10 dB | Enough |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 102.0 dB/mW | 0.63 mW | +16 dB | Comfortable |
| HiFiMAN HE400se | 25 Ω | 91.0 dB | 7.9 mW | +13 dB | Comfortable |
| HiFiMAN Sundara | 32 Ω | 92.0 dB | 6.3 mW | +15 dB | Comfortable |
| Dan Clark Audio Stealth | 23 Ω | 90.0 dB/mW | 10 mW | +12 dB | Comfortable |
| Fostex T50RP MK3 | 50 Ω | 92.0 dB/mW | 6.3 mW | +13 dB | Comfortable |
| AKG K702 | 62 Ω | 92.9 dB/mW | 5.1 mW | +13 dB | Comfortable |
| ZMF Verite Closed | 300 Ω | 99.0 dB/mW | 1.3 mW | +13 dB | Comfortable |
| Sennheiser HD 650 | 300 Ω | 97.8 dB/mW | 1.7 mW | +11 dB | Comfortable |
| Sennheiser HD 800S | 300 Ω | 96.8 dB/mW | 2.1 mW | +10 dB | Comfortable |
| Beyerdynamic DT 770 Pro (250Ω) | 250 Ω | 96.0 dB | 2.5 mW | +10 dB | Comfortable |
| Audio-Technica ATH-R70X | 470 Ω | 98.0 dB/mW | 1.6 mW | +10 dB | Enough |
| ZMF Atrium | 300 Ω | 96.0 dB/mW | 2.5 mW | +10 dB | Enough |
| Abyss AB-1266 Phi TC | 50 Ω | 88.0 dB/mW | 16 mW | +9 dB | Enough |
| Sennheiser HD 600 | 300 Ω | 91.8 dB/mW | 6.6 mW | +5 dB | Enough |
| HiFiMAN Susvara | 60 Ω | 83.0 dB | 50 mW | +3 dB | Enough |
The manufacturer does not publish an output noise figure for this source, so there is no hiss estimate here. If you have a measured figure, the hiss calculator takes it.
At 1Ω output impedance, the one-eighth rule says this source suits headphones of 8.0Ω and above. 15 of the 567 models here fall below that. Most of them are multi-driver in-ears, and the mismatch tilts the frequency response audibly rather than subtly.
| Source | Type | Price | Into 300 Ω | Output impedance | Output noise |
|---|---|---|---|---|---|
| FiiO KA11 | USB dongle | $29 | 22 mW | 0.7 Ω | 1.7 µV |
| FiiO BTR13 | Bluetooth receiver | $59 | 10.0 mW | 0.6 Ω | 1.0 µV |
| FiiO KA3 | USB dongle | $79 | 14 mW | 0.5 Ω | 1.7 µV |
Of the 280 sources here, 83 do everything the RME Fireface UCX II does as a headphone output: reach 100 dB on every headphone it reaches and stay inside the one-eighth rule wherever it does. The cheapest of them is the FiiO KA11 at $29, against this one’s $1749 — $1720 less, and a USB dongle rather than an audio interface.
The cheaper one also publishes a noise figure, which the RME Fireface UCX II does not — so on the paperwork it is ahead, not merely level.
This counts the headphone output only; inputs, converters, the volume control and the build are outside it.
$1495 · 490 mW into 32Ω · output Ω not published
Compare →$1399 · 1.2 W into 32Ω · 0.1 Ω out
Compare →$1300 · 528 mW into 32Ω · 50 Ω out
Compare →$2199 · 3.0 W into 32Ω · 0.1 Ω out
Compare →$999 · 225 mW into 32Ω · output Ω not published
Compare →$2499 · 1.9 W into 32Ω · 0.1 Ω out
Compare →Compared with its closest rivals: vs Apogee Symphony Desktop · vs Audient iD48 · vs Merging Anubis · vs RME ADI-2 DAC FS · vs RME ADI-2 Pro EX · vs RME ADI-2 Pro FS R · vs RME Babyface Pro FS · vs RME Fireface UFX II · vs RME Fireface UFX III.