Short answer
Both are audio interfaces, both at $199.
The Universal Audio Volt 2 reaches 100 dB on 558 of the 567 models here, the Focusrite Scarlett 2i2 4th gen on 552.
| Specification | Focusrite Scarlett 2i2 4th gen | Universal Audio Volt 2 |
|---|---|---|
| Power into 32Ω | 31 mW | 84 mW |
| Power into 150Ω | 19 mW | 28 mW |
| Power into 300Ω | 22 mW | 22 mW |
| Power into 600Ω | 11 mW | 12 mW |
| Output impedance | 50 Ω | not published |
| Output noise | not published | not published |
| Price | $199 | $199 |
| 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 | Universal Audio Volt 2 |
|---|---|---|
| 32 Ω | Derived | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Published | Published |
| 600 Ω | Derived | Published |
Both makers publish a power rating. Focusrite Scarlett 2i2 4th gen publishes at 300 Ω; Universal Audio Volt 2 at 32 Ω, at 300 Ω and at 600 Ω. The other rows are worked out from those.
So the two columns are not equally firm row by row: at 32 Ω and at 600 Ω only the Universal Audio Volt 2 figure is the maker’s own. On those rows the derived number is the one to doubt first.
6 headphones reach 100 dB on the Universal Audio Volt 2 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 HE400se: Universal Audio Volt 2 has +9 dB of headroom there against +5 dB. 4 dB is about 2.7 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 Universal Audio Volt 2 because neither maker publishes no output noise figure.
| Headphone | Impedance | Needs | Focusrite Scarlett 2i2 4th gen headroom | Universal Audio Volt 2 headroom | Focusrite Scarlett 2i2 4th gen hiss | Universal Audio Volt 2 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 | +18 dB | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +15 dB damping | +16 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 | +10 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +5 dB damping | +5 dB | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | -3 dB damping | +0 dB | not published | not published |
These two cost the same, $199, so price settles nothing. Out of the 567 models here, the Universal Audio Volt 2 drives 6 models to 100 dB — and on the other side there is no such advantage at all.
Only published figures count here; blank axes are counted separately.
Each in full: Focusrite Scarlett 2i2 4th gen and Universal Audio Volt 2.