Short answer
Both are audio interfaces, $229 against $150.
The SSL 2 MkII reaches 100 dB on 565 of the 567 models here, the Zoom AMS-24 on 549.
| Specification | SSL 2 MkII | Zoom AMS-24 |
|---|---|---|
| Power into 32Ω | 374 mW | 30 mW |
| Power into 150Ω | 80 mW | 9.7 mW |
| Power into 300Ω | 40 mW | 5.2 mW |
| Power into 600Ω | 20 mW | 2.7 mW |
| Output impedance | 1 Ω | 10 Ω |
| Output noise | not published | not published |
| Price | $229 | $150 |
| Headphones it reaches 100 dB on out of 567 | 565 | 549 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Load | SSL 2 MkII | Zoom AMS-24 |
|---|---|---|
| 32 Ω | Upper bound | Published |
| 150 Ω | Upper bound | Derived |
| 300 Ω | Upper bound | Derived |
| 600 Ω | Upper bound | Derived |
These two columns are not the same kind of number, and that matters more than the gap between them. Zoom AMS-24 publishes a power rating (at 32 Ω); SSL 2 MkII publishes no power figure at any load, only a maximum output voltage, so every milliwatt in its column is a ceiling worked out from that voltage.
A ceiling assumes the amplifier holds that voltage into the load, and nothing on SSL 2 MkII’s own sheet says it does. It is the most flattering reading available, and it is used here only because the alternative is a blank. Where the SSL 2 MkII column looks the stronger of the two, treat the difference as unproven rather than measured. 24 of the 280 sources here are in that position, with no published power rating at any load.
16 headphones reach 100 dB on the SSL 2 MkII but not on the Zoom AMS-24 — HiFiMAN HE-6se V2, HiFiMAN HE6 Remastered, HiFiMAN Susvara, 13 more.
495 headphones are left alone by the SSL 2 MkII under the one-eighth rule but coloured by the Zoom AMS-24 (64 Audio Aspire 1, 64 Audio Fourte, 64 Audio Ocean, 492 more).
549 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 Shure SE846: SSL 2 MkII has +34 dB of headroom there against +23 dB. 11 dB is about 12 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for SSL 2 MkII and Zoom AMS-24 because neither maker publishes no output noise figure.
| Headphone | Impedance | Needs | SSL 2 MkII headroom | Zoom AMS-24 headroom | SSL 2 MkII hiss | Zoom AMS-24 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +34 dB | +23 dB damping | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +14 dB | +3 dB damping | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +23 dB | +13 dB damping | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +19 dB | +10 dB | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +16 dB | +5 dB damping | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +12 dB | +3 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +8 dB | -1 dB | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | +6 dB | -4 dB damping | not published | not published |
The SSL 2 MkII costs $79 more than the Zoom AMS-24. Out of the 567 models here, that difference buys 16 more models driven to 100 dB and 495 more models left alone under the one-eighth rule.
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: SSL 2 MkII and Zoom AMS-24.