Short answer
Both are audio interfaces, $139 against $100.
The Focusrite Scarlett Solo 4th gen reaches 100 dB on 552 of the 567 models here, the Zoom AMS-22 on 538.
| Specification | Focusrite Scarlett Solo 4th gen | Zoom AMS-22 |
|---|---|---|
| Power into 32Ω | 31 mW | 20 mW |
| Power into 150Ω | 19 mW | 6.5 mW |
| Power into 300Ω | 22 mW | 3.4 mW |
| Power into 600Ω | 11 mW | 1.8 mW |
| Output impedance | 50 Ω | 10 Ω |
| Output noise | not published | not published |
| Price | $139 | $100 |
| Headphones it reaches 100 dB on out of 567 | 552 | 538 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Load | Focusrite Scarlett Solo 4th gen | Zoom AMS-22 |
|---|---|---|
| 32 Ω | Derived | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Published | Derived |
| 600 Ω | Derived | Derived |
Both makers publish a power rating. Focusrite Scarlett Solo 4th gen publishes at 300 Ω; Zoom AMS-22 at 32 Ω. The other rows are worked out from those.
So the two columns are not equally firm row by row: at 300 Ω only the Focusrite Scarlett Solo 4th gen figure is the maker’s own and at 32 Ω only the Zoom AMS-22 figure is the maker’s own. On those rows the derived number is the one to doubt first.
14 headphones reach 100 dB on the Focusrite Scarlett Solo 4th gen but not on the Zoom AMS-22 — Abyss AB-1266 Phi TC, Audeze LCD-5, Beyerdynamic DT 880 Edition (600Ω), 11 more.
51 headphones are left alone by the Zoom AMS-22 under the one-eighth rule but coloured by the Focusrite Scarlett Solo 4th gen (AKG K612 Pro, Audeze LCD-3, Audeze LCD-4, 48 more).
538 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 -3 dB. 8 dB is about 6.5 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Focusrite Scarlett Solo 4th gen and Zoom AMS-22 because neither maker publishes no output noise figure.
| Headphone | Impedance | Needs | Focusrite Scarlett Solo 4th gen headroom | Zoom AMS-22 headroom | Focusrite Scarlett Solo 4th gen hiss | Zoom AMS-22 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +23 dB damping | +22 dB damping | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +3 dB damping | +2 dB damping | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +14 dB damping | +11 dB damping | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +15 dB damping | +8 dB | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +5 dB damping | +3 dB damping | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +9 dB | +2 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 | -6 dB damping | not published | not published |
The Focusrite Scarlett Solo 4th gen costs $39 more than the Zoom AMS-22. Out of the 567 models here, that difference buys 14 more models driven to 100 dB.
It does not run one way only: the cheaper Zoom AMS-22 leaves 51 models alone under the one-eighth rule that the Focusrite Scarlett Solo 4th gen does not, which is the part worth checking against your own headphones before paying the difference.
Only published figures count here; blank axes are counted separately.
Each in full: Focusrite Scarlett Solo 4th gen and Zoom AMS-22.