Short answer
Both are audio interfaces, $130 against $199.
The IK Multimedia AXE I/O ONE reaches 100 dB on 550 of the 567 models here, the Tascam US-2x2HR on 541.
| Specification | IK Multimedia AXE I/O ONE | Tascam US-2x2HR |
|---|---|---|
| Power into 32Ω | 26 mW | 18 mW |
| Power into 150Ω | 13 mW | 17 mW |
| Power into 300Ω | 6.7 mW | 12 mW |
| Power into 600Ω | 3.3 mW | 7.3 mW |
| Output impedance | <0.1 Ω | 66 Ω |
| Output noise | not published | not published |
| Price | $130 | $199 |
| Headphones it reaches 100 dB on out of 567 | 550 | 541 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Load | IK Multimedia AXE I/O ONE | Tascam US-2x2HR |
|---|---|---|
| 32 Ω | Derived | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Derived | Derived |
| 600 Ω | Derived | Derived |
Only one of these two columns starts from a power rating. Tascam US-2x2HR publishes one at 32 Ω; IK Multimedia AXE I/O ONE 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 IK Multimedia AXE I/O ONE understates rather than flatters — but at 32 Ω is the only load here at which its maker can be held to a figure.
9 headphones reach 100 dB on the IK Multimedia AXE I/O ONE but not on the Tascam US-2x2HR — Abyss AB-1266 Phi TC, Audeze LCD-5, Dan Clark Audio AEON 2 Closed, 6 more.
564 headphones are left alone by the IK Multimedia AXE I/O ONE under the one-eighth rule but coloured by the Tascam US-2x2HR (64 Audio Aspire 1, 64 Audio Fourte, 64 Audio Nio, 561 more).
541 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 HiFiMAN Susvara: IK Multimedia AXE I/O ONE has -2 dB of headroom there against -5 dB. 3 dB is about 2.2 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 ONE and Tascam US-2x2HR because neither maker publishes no output noise figure.
| Headphone | Impedance | Needs | IK Multimedia AXE I/O ONE headroom | Tascam US-2x2HR headroom | IK Multimedia AXE I/O ONE hiss | Tascam US-2x2HR hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +23 dB | +21 dB damping | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +3 dB | +1 dB damping | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +16 dB | +13 dB damping | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +11 dB | +13 dB damping | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +4 dB | +2 dB damping | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +4 dB | +7 dB damping | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +0 dB | +3 dB damping | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | -2 dB | -5 dB damping | not published | not published |
The Tascam US-2x2HR costs $69 more than the IK Multimedia AXE I/O ONE, and on these three axes the money buys nothing: among the 567 models here there is not one that the Tascam US-2x2HR handles and the IK Multimedia AXE I/O ONE does not — not on power, not on the one-eighth rule, not on hiss. The traffic runs the other way: the cheaper IK Multimedia AXE I/O ONE drives 9 models to 100 dB and leaves 564 alone under the one-eighth rule that the Tascam US-2x2HR does not.
Only published figures count here; blank axes are counted separately.
Each in full: IK Multimedia AXE I/O ONE and Tascam US-2x2HR.