Both are desktop amplifiers, $539 against $600. This page puts them side by side on the only three things a maker can be held to — power, output impedance and noise — and then asks the question that actually matters: which headphones do they treat differently?
The SMSL H400 MK2 reaches 100 dB on 567 of the 567 models here, the Soncoz SGA1 on 566.
| Specification | SMSL H400 MK2 | Soncoz SGA1 |
|---|---|---|
| Power into 32Ω | 2.5 W | 407 mW |
| Power into 150Ω | 527 mW | 207 mW |
| Power into 300Ω | 260 mW | 210 mW |
| Power into 600Ω | 130 mW | 105 mW |
| Output impedance | <0.1 Ω | 0.1 Ω |
| Output noise | not published | 1.8 µV |
| Price | $539 | $600 |
| Headphones it reaches 100 dB on out of 567 | 567 | 566 |
A figure marked not published is missing from the maker’s own material, which is not the same as being good or bad. Where one of these two publishes a number and the other does not, the comparison on that axis cannot be made at all — and saying so is more useful than guessing.
| Load | SMSL H400 MK2 | Soncoz SGA1 |
|---|---|---|
| 32 Ω | Published | Derived |
| 150 Ω | Derived | Derived |
| 300 Ω | Published | Published |
| 600 Ω | Published | Published |
Both makers publish a power rating, which is less common than the table above makes it look: of the 280 sources here, 209 publish a figure at at least one load and only 2 publish one at all four. SMSL H400 MK2 publishes at 32 Ω, at 300 Ω and at 600 Ω; Soncoz SGA1 at 300 Ω and at 600 Ω. Every other row is worked out from those — between two published loads, or beyond them holding voltage constant, which understates rather than flatters.
So the two columns are not equally firm row by row: at 32 Ω only the SMSL H400 MK2 figure is the maker’s own. On those rows the derived number is the one to doubt first.
What each of these labels means, and why a derived figure is still worth printing, is set out in how this data was built.
1 headphone reaches 100 dB on the SMSL H400 MK2 but not on the Soncoz SGA1 — Symphonium Titan.
566 of the 567 models here reach 100 dB on both. That is a power count and nothing more; whether either source suits a given headphone also depends on the two lines above.
The counts above say how many models the two treat differently. This says by how much. The same 8 headphones appear on every page of this kind, ordered from the easiest to drive to the hardest, so a row can be read across pages as well as across columns. 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 +15 dB. 14 dB is about 25 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. That is a gap in the specification, not a quiet amplifier, and it is left blank here rather than filled with a plausible number.
| Headphone | Impedance | Needs | SMSL H400 MK2 headroom | Soncoz SGA1 headroom | SMSL H400 MK2 hiss | Soncoz SGA1 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +48 dB | +35 dB | not published | 20 dB |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +28 dB | +15 dB | not published | -0 dB |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +32 dB | +25 dB | not published | -2 dB |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +27 dB | +25 dB | not published | -7 dB |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +26 dB | +16 dB | not published | -8 dB |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +20 dB | +19 dB | not published | -14 dB |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +16 dB | +15 dB | not published | -18 dB |
| HiFiMAN Susvara | 60 Ω | 50 mW | +14 dB | +8 dB | not published | -20 dB |
The Soncoz SGA1 costs $61 more than the SMSL H400 MK2, and on these three axes the money buys nothing: among the 567 models here there is not one that the Soncoz SGA1 handles and the SMSL H400 MK2 does not — not on power, not on the one-eighth rule, not on hiss. The traffic runs the other way: the cheaper SMSL H400 MK2 drives one model to 100 dB that the Soncoz SGA1 does not.
Everything in this paragraph counts only figures the two makers published. An advantage on an axis one of them leaves blank cannot be counted, and is not counted — how often that happens is its own page.
Each has a page of its own with every power figure traced to what the maker published and a full headphone list: SMSL H400 MK2 and Soncoz SGA1. Or put either against your own headphones in the source comparison tool.