Short answer
Both are desktop amplifiers, $499 against $539.
The SMSL H400 MK2 reaches 100 dB on 567 of the 567 models here, the Schiit Valhalla 3 on 566.
| Specification | Schiit Valhalla 3 | SMSL H400 MK2 |
|---|---|---|
| Power into 32Ω | 750 mW | 2.5 W |
| Power into 150Ω | 286 mW | 527 mW |
| Power into 300Ω | 250 mW | 260 mW |
| Power into 600Ω | 125 mW | 130 mW |
| Output impedance | 25 Ω | <0.1 Ω |
| Output noise | 6.32 µV | not published |
| Price | $499 | $539 |
| Headphones it reaches 100 dB on out of 567 | 566 | 567 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Balanced | Schiit Valhalla 3 | SMSL H400 MK2 |
|---|---|---|
| Socket | no separate rating | 4.4mm / 4-pin XLR |
| Power into 32Ω | — | 9.0 W |
| Power into 300Ω | — | 1.1 W |
| Output impedance | — | <0.1 Ω |
| Output noise | — | not published |
| Headphones it reaches 100 dB on out of 567 | — | 567 |
Only the SMSL H400 MK2 has a separate balanced rating from its maker; through it, it reaches 100 dB on 567 of the 567 models here. The Schiit Valhalla 3 may still have a balanced socket — its spec sheet simply gives no figure for one, so there is nothing to put beside it.
| Load | Schiit Valhalla 3 | SMSL H400 MK2 |
|---|---|---|
| 32 Ω | Published | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Published | Published |
| 600 Ω | Derived | Published |
Both makers publish a power rating. Schiit Valhalla 3 publishes at 32 Ω and at 300 Ω; SMSL H400 MK2 at 32 Ω, at 300 Ω and at 600 Ω. The other rows are worked out from those.
So the two columns are not equally firm row by row: at 600 Ω only the SMSL H400 MK2 figure is the maker’s own. On those rows the derived number is the one to doubt first.
1 headphone reaches 100 dB on the SMSL H400 MK2 but not on the Schiit Valhalla 3 — Symphonium Titan.
535 headphones are left alone by the SMSL H400 MK2 under the one-eighth rule but coloured by the Schiit Valhalla 3 (64 Audio Aspire 1, 64 Audio Fourte, 64 Audio Nio, 532 more).
566 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: SMSL H400 MK2 has +28 dB of headroom there against +17 dB. 11 dB is about 13 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for SMSL H400 MK2 because that maker publishes no output noise figure.
| Headphone | Impedance | Needs | Schiit Valhalla 3 headroom | SMSL H400 MK2 headroom | Schiit Valhalla 3 hiss | SMSL H400 MK2 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +37 dB damping | +48 dB | 30 dB | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +17 dB damping | +28 dB | 10 dB | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +27 dB damping | +32 dB | 9 dB | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +26 dB | +27 dB | 4 dB | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +19 dB damping | +26 dB | 3 dB | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +20 dB | +20 dB | -3 dB | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +16 dB | +16 dB | -7 dB | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | +10 dB damping | +14 dB | -9 dB | not published |
The SMSL H400 MK2 costs $40 more than the Schiit Valhalla 3. Out of the 567 models here, that difference buys 1 more model driven to 100 dB and 535 more models left alone under the one-eighth rule.
Nothing runs the other way: there is no axis here on which the cheaper of the two does better.
Only published figures count here; blank axes are counted separately.
Each in full: Schiit Valhalla 3 and SMSL H400 MK2.