Both are audio interfaces, $400 against $399. This page puts them side by side on the only three things a maker can be held to — power, output impedance and noise — and then asks the question that actually matters: which headphones do they treat differently?
The Zoom UAC-232 reaches 100 dB on 563 of the 567 models here, the IK Multimedia AXE I/O on 561.
| Specification | IK Multimedia AXE I/O | Zoom UAC-232 |
|---|---|---|
| Power into 32Ω | 115 mW | 148 mW |
| Power into 150Ω | 60 mW | 51 mW |
| Power into 300Ω | 30 mW | 28 mW |
| Power into 600Ω | 15 mW | 14 mW |
| Output impedance | <0.1 Ω | 12 Ω |
| Output noise | not published | not published |
| Price | $400 | $399 |
| Headphones it reaches 100 dB on out of 567 | 561 | 563 |
A figure marked not published is missing from the maker’s own material, which is not the same as being good or bad. Where one of these two publishes a number and the other does not, the comparison on that axis cannot be made at all — and saying so is more useful than guessing.
| Load | IK Multimedia AXE I/O | Zoom UAC-232 |
|---|---|---|
| 32 Ω | Derived | Derived |
| 150 Ω | Derived | Derived |
| 300 Ω | Derived | Derived |
| 600 Ω | Derived | Derived |
Neither column is a maker’s power rating at these loads. Of the 280 sources here, 209 publish a figure at at least one load; these two do not, so every row above is derived — between or beyond the loads each maker did publish, holding output voltage as the maker’s own figures imply. The method understates rather than flatters, but it is still arithmetic rather than a rating.
What each of these labels means, and why a derived figure is still worth printing, is set out in how this data was built.
2 headphones reach 100 dB on the Zoom UAC-232 but not on the IK Multimedia AXE I/O — Moondrop COSMO, Symphonium Zenith.
520 headphones are left alone by the IK Multimedia AXE I/O under the one-eighth rule but coloured by the Zoom UAC-232 (64 Audio Aspire 1, 64 Audio Fourte, 64 Audio Nio, 517 more).
561 of the 567 models here reach 100 dB on both. That is a power count and nothing more; whether either source suits a given headphone also depends on the two lines above.
The counts above say how many models the two treat differently. This says by how much. The same 8 headphones appear on every page of this kind, ordered from the easiest to drive to the hardest, so a row can be read across pages as well as across columns. Headroom is at a 100 dB SPL peak.
The widest gap on the list is the HiFiMAN Susvara: IK Multimedia AXE I/O has +5 dB of headroom there against +3 dB. 2 dB is about 1.5 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for IK Multimedia AXE I/O and Zoom UAC-232 because neither maker publishes no output noise figure. That is a gap in the specification, not a quiet amplifier, and it is left blank here rather than filled with a plausible number.
| Headphone | Impedance | Needs | IK Multimedia AXE I/O headroom | Zoom UAC-232 headroom | IK Multimedia AXE I/O hiss | Zoom UAC-232 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +29 dB | +30 dB damping | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +9 dB | +10 dB damping | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +22 dB | +21 dB damping | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +18 dB | +17 dB | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +11 dB | +12 dB damping | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +11 dB | +11 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +7 dB | +6 dB | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | +5 dB | +3 dB damping | not published | not published |
The IK Multimedia AXE I/O costs $1 more than the Zoom UAC-232. Out of the 567 models here, that difference buys 520 more models left alone under the one-eighth rule.
It does not run one way only: the cheaper Zoom UAC-232 drives 2 models to 100 dB that the IK Multimedia AXE I/O does not, which is the part worth checking against your own headphones before paying the difference.
Everything in this paragraph counts only figures the two makers published. An advantage on an axis one of them leaves blank cannot be counted, and is not counted — how often that happens is its own page.
Each has a page of its own with every power figure traced to what the maker published and a full headphone list: IK Multimedia AXE I/O and Zoom UAC-232. Or put either against your own headphones in the source comparison tool.