Short answer
Both are audio interfaces, $199 against $200.
The Audient iD4 MkII reaches 100 dB on 561 of the 567 models here, the Zoom AMS-44 on 549.
| Specification | Audient iD4 MkII | Zoom AMS-44 |
|---|---|---|
| Power into 32Ω | 112 mW | 30 mW |
| Power into 150Ω | 75 mW | 9.7 mW |
| Power into 300Ω | 55 mW | 5.2 mW |
| Power into 600Ω | 50 mW | 2.7 mW |
| Output impedance | not published | 10 Ω |
| Output noise | not published | not published |
| Price | $199 | $200 |
| Headphones it reaches 100 dB on out of 567 | 561 | 549 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Load | Audient iD4 MkII | Zoom AMS-44 |
|---|---|---|
| 32 Ω | Derived | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Derived | Derived |
| 600 Ω | Recomputed | Derived |
Only one of these two columns starts from a power rating. Zoom AMS-44 publishes one at 32 Ω; Audient iD4 MkII 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 iD4 MkII understates rather than flatters — but at 32 Ω is the only load here at which its maker can be held to a figure.
12 headphones reach 100 dB on the Audient iD4 MkII but not on the Zoom AMS-44 — HiFiMAN HE-6se V2, HiFiMAN HE6 Remastered, HiFiMAN Susvara, 9 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 Audio-Technica ATH-R70X: Audient iD4 MkII has +15 dB of headroom there against +3 dB. 12 dB is about 15 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Audient iD4 MkII and Zoom AMS-44 because neither maker publishes no output noise figure.
| Headphone | Impedance | Needs | Audient iD4 MkII headroom | Zoom AMS-44 headroom | Audient iD4 MkII hiss | Zoom AMS-44 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +29 dB | +23 dB damping | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +9 dB | +3 dB damping | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +22 dB | +13 dB damping | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +20 dB | +10 dB | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +11 dB | +5 dB damping | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +15 dB | +3 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +9 dB | -1 dB | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | +4 dB | -4 dB damping | not published | not published |
The Zoom AMS-44 costs $1 more than the Audient iD4 MkII, and on these three axes the money buys nothing: among the 567 models here there is not one that the Zoom AMS-44 handles and the Audient iD4 MkII does not — not on power, not on the one-eighth rule, not on hiss. The traffic runs the other way: the cheaper Audient iD4 MkII drives 12 models to 100 dB that the Zoom AMS-44 does not.
Only published figures count here; blank axes are counted separately.
Each in full: Audient iD4 MkII and Zoom AMS-44.