Short answer
Both are dongles, $259 against $200.
The THX Onyx reaches 100 dB on 565 of the 567 models here, the Shanling UA5 on 562.
| Specification | Shanling UA5 | THX Onyx |
|---|---|---|
| Power into 32Ω | 137 mW | 124 mW |
| Power into 150Ω | 29 mW | 26 mW |
| Power into 300Ω | 15 mW | 13 mW |
| Power into 600Ω | 7.3 mW | 6.6 mW |
| Output impedance | 0.8 Ω | 0.2 Ω |
| Output noise | 3.5 µV unverified | not published |
| Price | $259 | $200 |
| Headphones it reaches 100 dB on out of 567 | 562 | 565 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Balanced | Shanling UA5 | THX Onyx |
|---|---|---|
| Socket | 4.4mm | no separate rating |
| Power into 32Ω | 211 mW | — |
| Power into 300Ω | 22 mW derived | — |
| Output impedance | 1.6 Ω | — |
| Output noise | not published | — |
| Headphones it reaches 100 dB on out of 567 | 564 | — |
Only the Shanling UA5 has a separate balanced rating from its maker; through it, it reaches 100 dB on 564 of the 567 models here. The THX Onyx may still have a balanced socket — its spec sheet simply gives no figure for one, so there is nothing to put beside it. Derived figures are worked out from the loads the maker did publish.
| Load | Shanling UA5 | THX Onyx |
|---|---|---|
| 32 Ω | Published | Derived |
| 150 Ω | Derived | Derived |
| 300 Ω | Derived | Derived |
| 600 Ω | Derived | Derived |
Only one of these two columns starts from a power rating. Shanling UA5 publishes one at 32 Ω; THX Onyx 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 THX Onyx understates rather than flatters — but at 32 Ω is the only load here at which its maker can be held to a figure.
3 headphones reach 100 dB on the THX Onyx but not on the Shanling UA5 — Moondrop COSMO, Symphonium Crimson, Symphonium Helios.
12 headphones are left alone by the THX Onyx under the one-eighth rule but coloured by the Shanling UA5 (64 Audio Nio, 64 Audio Volur, Campfire Audio Andromeda 2023, 9 more).
562 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 Campfire Audio Andromeda 2020: THX Onyx has +13 dB of headroom there against +10 dB. 3 dB is about 1.9 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Shanling UA5 and THX Onyx because neither maker publishes no output noise figure.
| Headphone | Impedance | Needs | Shanling UA5 headroom | THX Onyx headroom | Shanling UA5 hiss | THX Onyx hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +30 dB | +33 dB | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +10 dB | +13 dB | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +19 dB | +19 dB | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +14 dB | +14 dB | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +11 dB | +13 dB | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +8 dB | +7 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +3 dB | +3 dB | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | +2 dB | +1 dB | not published | not published |
The Shanling UA5 costs $59 more than the THX Onyx, and on these three axes the money buys nothing: among the 567 models here there is not one that the Shanling UA5 handles and the THX Onyx does not — not on power, not on the one-eighth rule, not on hiss. The traffic runs the other way: the cheaper THX Onyx drives 3 models to 100 dB and leaves 12 alone under the one-eighth rule that the Shanling UA5 does not.
Only published figures count here; blank axes are counted separately.
Each in full: Shanling UA5 and THX Onyx.