Short answer
Both are desktop amplifiers, $499 against $529.
The SMSL SP400 reaches 100 dB on 567 of the 567 models here, the Schiit Valhalla 3 on 566.
| Specification | Schiit Valhalla 3 | SMSL SP400 |
|---|---|---|
| Power into 32Ω | 750 mW | 3.0 W |
| Power into 150Ω | 286 mW | 741 mW |
| Power into 300Ω | 250 mW | 440 mW |
| Power into 600Ω | 125 mW | 220 mW |
| Output impedance | 25 Ω | <0.1 Ω |
| Output noise | 6.32 µV | 1.9 µV |
| Price | $499 | $529 |
| Headphones it reaches 100 dB on out of 567 | 566 | 567 |
| Balanced | Schiit Valhalla 3 | SMSL SP400 |
|---|---|---|
| Socket | no separate rating | XLR4 |
| Power into 32Ω | — | 6.0 W |
| Power into 300Ω | — | 880 mW |
| Output impedance | — | <0.1 Ω |
| Output noise | — | 1.9 µV |
| Headphones it reaches 100 dB on out of 567 | — | 567 |
Only the SMSL SP400 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 SP400 |
|---|---|---|
| 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 SP400 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 SP400 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 SP400 but not on the Schiit Valhalla 3 — Symphonium Titan.
535 headphones are left alone by the SMSL SP400 under the one-eighth rule but coloured by the Schiit Valhalla 3 (64 Audio Aspire 1, 64 Audio Fourte, 64 Audio Nio, 532 more).
98 headphones stay below the audible-hiss threshold on the SMSL SP400 but cross it on the Schiit Valhalla 3 (64 Audio Fourte, 64 Audio Nio, 64 Audio U12t, 95 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 Shure SE846: SMSL SP400 has +49 dB of headroom there against +37 dB. 12 dB is about 16 times the power, which matters for peaks rather than for how loud the music sits.
Hiss below about 20 dB SPL is inaudible in a quiet room.
| Headphone | Impedance | Needs | Schiit Valhalla 3 headroom | SMSL SP400 headroom | Schiit Valhalla 3 hiss | SMSL SP400 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +37 dB damping | +49 dB | 30 dB | 20 dB |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +17 dB damping | +29 dB | 10 dB | 0 dB |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +27 dB damping | +33 dB | 9 dB | -2 dB |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +26 dB | +29 dB | 4 dB | -6 dB |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +19 dB damping | +27 dB | 3 dB | -7 dB |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +20 dB | +22 dB | -3 dB | -13 dB |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +16 dB | +18 dB | -7 dB | -17 dB |
| HiFiMAN Susvara | 60 Ω | 50 mW | +10 dB damping | +15 dB | -9 dB | -19 dB |
The SMSL SP400 costs $30 more than the Schiit Valhalla 3. Out of the 567 models here, that difference buys 1 more model driven to 100 dB, 535 more models left alone under the one-eighth rule and 98 more models kept below the audible-hiss threshold.
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 SP400.