The SMSL SP400 is a desktop amplifier at $529. It delivers 3.0 W into 32Ω and 440 mW into 300Ω, which ranks it 21 of 280 for raw power among the sources in this database.
Measured at 100 dB SPL it has comfortable headroom on 567 of the 567 dynamic and planar headphones catalogued here. THX AAA topology with a proper split between balanced and single-ended ratings.
The shop listings these figures stand on quote 6.0 W into 16Ω, 3.0 W into 32Ω, 440 mW into 300Ω, 220 mW into 600Ω. The rest of the table is worked out from those.
The balanced output is rated separately: 6.0 W into 32Ω through the XLR4 jack.
Derived rows hold output voltage steady, as an amplifier does (method).
One caveat about the source. None of the addresses below is a SMSL document. The figures here stand on Audiophonics, a French retailer, which is a transcription of the factory table rather than the table itself. A transcription is usually faithful and may well be exact here — but it can carry an old revision, and nothing on this site would notice if it did. Find these numbers on SMSL's own site and send the link; this paragraph comes off.
Source: audiophonics.fr.
| Load | Power | Status | How it was arrived at |
|---|---|---|---|
| 16 Ω | 6.0 W | Quoted by a shop | a shop or distributor listing quotes this figure at this exact load; the maker publishes nothing this site could find |
| 32 Ω | 3.0 W | Quoted by a shop | a shop or distributor listing quotes this figure at this exact load; the maker publishes nothing this site could find |
| 150 Ω | 741 mW | Derived | worked out between two published loads, holding output voltage linear between them |
| 300 Ω | 440 mW | Quoted by a shop | a shop or distributor listing quotes this figure at this exact load; the maker publishes nothing this site could find |
| 600 Ω | 220 mW | Quoted by a shop | a shop or distributor listing quotes this figure at this exact load; the maker publishes nothing this site could find |
Easiest to hardest to drive, with headroom at a 100 dB SPL peak.
| Headphone | Impedance | Sensitivity | Needs | Headroom | Verdict |
|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 114.0 dB/mW | 0.04 mW | +49 dB | Comfortable audible hiss |
| 64 Audio U12t | 12.6 Ω | 108.0 dB/mW | 0.16 mW | +45 dB | Comfortable audible hiss |
| Shure SE215 | 17 Ω | 107.0 dB/mW | 0.20 mW | +45 dB | Comfortable audible hiss |
| Moondrop Aria | 32 Ω | 107.1 dB/mW | 0.19 mW | +42 dB | Comfortable faint hiss |
| Audeze LCD-X 2021 | 20 Ω | 103.0 dB/mW | 0.50 mW | +40 dB | Comfortable faint hiss |
| Truthear Hexa | 20.5 Ω | 103.1 dB/mW | 0.49 mW | +40 dB | Comfortable faint hiss |
| Sennheiser IE 200 | 18 Ω | 101.6 dB/mW | 0.69 mW | +39 dB | Comfortable faint hiss |
| Sony MDR-7506 | 63 Ω | 106.0 dB/mW | 0.25 mW | +38 dB | Comfortable faint hiss |
| Meze 99 Classics | 32 Ω | 103.0 dB/mW | 0.50 mW | +38 dB | Comfortable faint hiss |
| Focal Clear MG | 55 Ω | 104.0 dB/mW | 0.40 mW | +37 dB | Comfortable faint hiss |
| Philips SHP9500 | 32 Ω | 101.0 dB | 0.79 mW | +36 dB | Comfortable faint hiss |
| Focal Utopia | 80 Ω | 104.0 dB/mW | 0.40 mW | +35 dB | Comfortable faint hiss |
| Meze Empyrean | 32 Ω | 100.0 dB | 1.0 mW | +35 dB | Comfortable faint hiss |
| Campfire Audio Andromeda 2020 | 9 Ω | 94.0 dB | 4.0 mW | +29 dB | Comfortable faint hiss |
| Etymotic ER2SE | 15 Ω | 96.0 dB/mW | 2.5 mW | +34 dB | Comfortable |
| AKG K371 | 32 Ω | 99.1 dB/mW | 1.2 mW | +34 dB | Comfortable |
| Audio-Technica ATH-M50X | 38 Ω | 99.0 dB/mW | 1.3 mW | +33 dB | Comfortable |
| Beyerdynamic DT 900 Pro X | 48 Ω | 100.0 dB/mW | 1.0 mW | +33 dB | Comfortable |
| Audeze LCD-2 Classic | 70 Ω | 101.0 dB/mW | 0.79 mW | +33 dB | Comfortable |
| Grado SR80x | 38 Ω | 98.0 dB/mW | 1.6 mW | +32 dB | Comfortable |
| Sennheiser HD 560S | 120 Ω | 100.8 dB/mW | 0.83 mW | +30 dB | Comfortable |
| HiFiMAN Edition XS | 18 Ω | 92.0 dB | 6.3 mW | +29 dB | Comfortable |
| HiFiMAN Arya Stealth | 32 Ω | 94.0 dB | 4.0 mW | +29 dB | Comfortable |
| Dan Clark Audio AEON 2 Closed | 13 Ω | 90.0 dB/mW | 10 mW | +27 dB | Comfortable |
| Audeze LCD-5 | 14 Ω | 90.0 dB/mW | 10 mW | +27 dB | Comfortable |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 102.0 dB/mW | 0.63 mW | +29 dB | Comfortable |
| HiFiMAN HE400se | 25 Ω | 91.0 dB | 7.9 mW | +27 dB | Comfortable |
| HiFiMAN Sundara | 32 Ω | 92.0 dB | 6.3 mW | +27 dB | Comfortable |
| Dan Clark Audio Stealth | 23 Ω | 90.0 dB/mW | 10 mW | +26 dB | Comfortable |
| Fostex T50RP MK3 | 50 Ω | 92.0 dB/mW | 6.3 mW | +25 dB | Comfortable |
| AKG K702 | 62 Ω | 92.9 dB/mW | 5.1 mW | +25 dB | Comfortable |
| ZMF Verite Closed | 300 Ω | 99.0 dB/mW | 1.3 mW | +25 dB | Comfortable |
| Sennheiser HD 650 | 300 Ω | 97.8 dB/mW | 1.7 mW | +24 dB | Comfortable |
| Sennheiser HD 800S | 300 Ω | 96.8 dB/mW | 2.1 mW | +23 dB | Comfortable |
| Beyerdynamic DT 770 Pro (250Ω) | 250 Ω | 96.0 dB | 2.5 mW | +23 dB | Comfortable |
| Audio-Technica ATH-R70X | 470 Ω | 98.0 dB/mW | 1.6 mW | +22 dB | Comfortable |
| ZMF Atrium | 300 Ω | 96.0 dB/mW | 2.5 mW | +22 dB | Comfortable |
| Abyss AB-1266 Phi TC | 50 Ω | 88.0 dB/mW | 16 mW | +21 dB | Comfortable |
| Sennheiser HD 600 | 300 Ω | 91.8 dB/mW | 6.6 mW | +18 dB | Comfortable |
| HiFiMAN Susvara | 60 Ω | 83.0 dB | 50 mW | +15 dB | Comfortable |
At 1.9 µV of output noise, here is where that noise lands in the five most revealing in-ears in the database.
This one hisses. With the most sensitive in-ears in the database its own noise lands around 27 dB SPL, which you will hear between tracks and in quiet passages.
| In-ear | Impedance | Sensitivity | Hiss level |
|---|---|---|---|
| Simgot EA500 | 16 Ω | 141.0 dB/V | 27 dB SPL |
| Tanchjim EA FORCE | 17 Ω | 137.7 dB/V | 23 dB SPL |
| Shure SE846 | 9 Ω | 134.5 dB/V | 20 dB SPL |
| Campfire Audio Clara | 13.3 Ω | 134.1 dB/V | 20 dB SPL |
| 64 Audio Fourte | 10 Ω | 134.0 dB/V | 20 dB SPL |
At 0Ω output impedance this source satisfies the one-eighth rule with every headphone in the database, down to the 3Ω in-ears. Nothing here will have its frequency response shaped by the source.
| Source | Type | Price | Into 300 Ω | Output impedance | Output noise |
|---|---|---|---|---|---|
| Schiit Magni Unity | desktop amplifier | $119 | 415 mW | 0.1 Ω | 1.59 µV |
| Topping L30 II | desktop amplifier | $149 | 560 mW | 0.1 Ω | 0.3 µV |
| SMSL HO100 | desktop amplifier | $160 | 200 mW | <0.1 Ω | 1.3 µV |
Of the 280 sources here, 7 do everything the SMSL SP400 does as a headphone output: reach 100 dB on every headphone it reaches, stay inside the one-eighth rule wherever it does and stay under the audible-hiss threshold wherever it does. The cheapest of them is the Schiit Magni Unity at $119, against this one’s $529 — $410 less.
This counts the headphone output only; inputs, converters, the volume control and the build are outside it.
$539 · 2.5 W into 32Ω · <0.1 Ω out
Compare →$540 · 2.5 W into 32Ω · output Ω not published
Compare →$499 · 2.0 W into 32Ω · 0.1 Ω out
Compare →$499 · 750 mW into 32Ω · 25 Ω out
Compare →$599 · 2.0 W into 32Ω · 0.1 Ω out
Compare →$600 · 4.0 W into 32Ω · 0.5 Ω out
Compare →Compared with its closest rivals: vs Bottlehead Crack (OTL kit) · vs Schiit Valhalla 3 · vs SMSL HO100 · vs SMSL HO200 · vs Topping A90.