Short answer
Both are audio interfaces, $129 against $139.
The Focusrite Scarlett Solo 4th gen reaches 100 dB on 552 of the 567 models here, the Audient EVO 4 on 543.
| Specification | Audient EVO 4 | Focusrite Scarlett Solo 4th gen |
|---|---|---|
| Power into 32Ω | 22 mW | 31 mW |
| Power into 150Ω | 14 mW | 19 mW |
| Power into 300Ω | 11 mW | 22 mW |
| Power into 600Ω | 10 mW | 11 mW |
| Output impedance | 50 Ω | 50 Ω |
| Output noise | not published | not published |
| Price | $129 | $139 |
| Headphones it reaches 100 dB on out of 567 | 543 | 552 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Load | Audient EVO 4 | Focusrite Scarlett Solo 4th gen |
|---|---|---|
| 32 Ω | Derived | Derived |
| 150 Ω | Derived | Derived |
| 300 Ω | Derived | Published |
| 600 Ω | Recomputed | Derived |
Only one of these two columns starts from a power rating. Focusrite Scarlett Solo 4th gen publishes one at 300 Ω; Audient EVO 4 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 Audient EVO 4 understates rather than flatters — but at 300 Ω is the only load here at which its maker can be held to a figure.
9 headphones reach 100 dB on the Focusrite Scarlett Solo 4th gen but not on the Audient EVO 4 — Dan Clark Audio AEON 2 Closed, Dan Clark Audio AEON 2 Noire, Dan Clark Audio AEON 2 Open, 6 more.
543 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 Sennheiser HD 600: Focusrite Scarlett Solo 4th gen has +5 dB of headroom there against +2 dB. 3 dB is twice the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Audient EVO 4 and Focusrite Scarlett Solo 4th gen because neither maker publishes no output noise figure.
| Headphone | Impedance | Needs | Audient EVO 4 headroom | Focusrite Scarlett Solo 4th gen headroom | Audient EVO 4 hiss | Focusrite Scarlett Solo 4th gen hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +22 dB damping | +23 dB damping | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +2 dB damping | +3 dB damping | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +15 dB damping | +14 dB damping | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +13 dB damping | +15 dB damping | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +4 dB damping | +5 dB damping | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +8 dB | +9 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +2 dB damping | +5 dB damping | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | -3 dB damping | -3 dB damping | not published | not published |
The Focusrite Scarlett Solo 4th gen costs $10 more than the Audient EVO 4. Out of the 567 models here, that difference buys 9 more models driven to 100 dB.
Nothing runs the other way: there is no axis here on which the cheaper of the two does better.
Only published figures count here; blank axes are counted separately.
Each in full: Audient EVO 4 and Focusrite Scarlett Solo 4th gen.