Short answer
Both are audio interfaces, $199 against $194.
The Steinberg UR24C reaches 100 dB on 558 of the 567 models here, the Focusrite Scarlett 2i2 4th gen on 552.
| Specification | Focusrite Scarlett 2i2 4th gen | Steinberg UR24C |
|---|---|---|
| Power into 32Ω | 31 mW | 80 mW |
| Power into 150Ω | 19 mW | 27 mW |
| Power into 300Ω | 22 mW | 13 mW |
| Power into 600Ω | 11 mW | 6.7 mW |
| Output impedance | 50 Ω | not published |
| Output noise | not published | not published |
| Price | $199 | $194 |
| Headphones it reaches 100 dB on out of 567 | 552 | 558 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Load | Focusrite Scarlett 2i2 4th gen | Steinberg UR24C |
|---|---|---|
| 32 Ω | Derived | Derived |
| 150 Ω | Derived | Derived |
| 300 Ω | Published | Derived |
| 600 Ω | Derived | Derived |
Only one of these two columns starts from a power rating. Focusrite Scarlett 2i2 4th gen publishes one at 300 Ω; Steinberg UR24C publishes none at any of these four loads, so its column is worked out from power it published at other loads. Both are arithmetic on a maker’s own figures rather than guesses, and the method used for the Steinberg UR24C understates rather than flatters — but at 300 Ω is the only load here at which its maker can be held to a figure.
6 headphones reach 100 dB on the Steinberg UR24C but not on the Focusrite Scarlett 2i2 4th gen — HiFiMAN HE-6se V2, HiFiMAN HE6 Remastered, HiFiMAN Susvara, 3 more.
552 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 HiFiMAN Susvara: Steinberg UR24C has +1 dB of headroom there against -3 dB. 5 dB is about 2.9 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Focusrite Scarlett 2i2 4th gen and Steinberg UR24C because neither maker publishes no output noise figure.
| Headphone | Impedance | Needs | Focusrite Scarlett 2i2 4th gen headroom | Steinberg UR24C headroom | Focusrite Scarlett 2i2 4th gen hiss | Steinberg UR24C hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +23 dB damping | +28 dB | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +3 dB damping | +8 dB | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +14 dB damping | +19 dB | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +15 dB damping | +14 dB | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +5 dB damping | +9 dB | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +9 dB | +7 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +5 dB damping | +3 dB | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | -3 dB damping | +1 dB | not published | not published |
The Focusrite Scarlett 2i2 4th gen costs $5 more than the Steinberg UR24C, and on these three axes the money buys nothing: among the 567 models here there is not one that the Focusrite Scarlett 2i2 4th gen handles and the Steinberg UR24C does not — not on power, not on the one-eighth rule, not on hiss. The traffic runs the other way: the cheaper Steinberg UR24C drives 6 models to 100 dB that the Focusrite Scarlett 2i2 4th gen does not.
Only published figures count here; blank axes are counted separately.
Each in full: Focusrite Scarlett 2i2 4th gen and Steinberg UR24C.