Short answer
Both are audio interfaces, both at $249.
The Tascam US-4x4HR reaches 100 dB on 553 of the 567 models here, the Audient EVO 8 on 543.
| Specification | Audient EVO 8 | Tascam US-4x4HR |
|---|---|---|
| Power into 32Ω | 22 mW | 45 mW |
| Power into 150Ω | 14 mW | 36 mW |
| Power into 300Ω | 11 mW | 24 mW |
| Power into 600Ω | 10 mW | 14 mW |
| Output impedance | 50 Ω | 51.5 Ω |
| Output noise | not published | not published |
| Price | $249 | $249 |
| Headphones it reaches 100 dB on out of 567 | 543 | 553 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Load | Audient EVO 8 | Tascam US-4x4HR |
|---|---|---|
| 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. Tascam US-4x4HR publishes one at 32 Ω; Audient EVO 8 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 EVO 8 understates rather than flatters — but at 32 Ω is the only load here at which its maker can be held to a figure.
10 headphones reach 100 dB on the Tascam US-4x4HR but not on the Audient EVO 8 — Dan Clark Audio AEON 2 Closed, Dan Clark Audio AEON 2 Noire, Dan Clark Audio AEON 2 Open, 7 more.
543 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 Beyerdynamic DT 1990 Pro (250Ω): Tascam US-4x4HR has +16 dB of headroom there against +13 dB. 4 dB is about 2.3 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Audient EVO 8 and Tascam US-4x4HR because neither maker publishes no output noise figure.
| Headphone | Impedance | Needs | Audient EVO 8 headroom | Tascam US-4x4HR headroom | Audient EVO 8 hiss | Tascam US-4x4HR hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +22 dB damping | +25 dB damping | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +2 dB damping | +5 dB damping | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +15 dB damping | +16 dB damping | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +13 dB damping | +16 dB damping | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +4 dB damping | +6 dB damping | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +8 dB | +10 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +2 dB damping | +6 dB damping | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | -3 dB damping | -1 dB damping | not published | not published |
These two cost the same, $249, so price settles nothing. Out of the 567 models here, the Tascam US-4x4HR drives 10 models to 100 dB — and on the other side there is no such advantage at all.
Only published figures count here; blank axes are counted separately.
Each in full: Audient EVO 8 and Tascam US-4x4HR.