Short answer
Both are desktop amplifiers, $100 against $99.
The Schiit Magni Heresy reaches 100 dB on 567 of the 567 models here, the Fosi Audio SK02 on 564.
| Specification | Fosi Audio SK02 | Schiit Magni Heresy |
|---|---|---|
| Power into 32Ω | 190 mW | 2.4 W |
| Power into 150Ω | 41 mW | 641 mW |
| Power into 300Ω | 20 mW | 410 mW |
| Power into 600Ω | 10 mW | 215 mW |
| Output impedance | not published | 0.25 Ω |
| Output noise | 3.7 µV | 1.5 µV unverified |
| Price | $100 | $99 |
| Headphones it reaches 100 dB on out of 567 | 564 | 567 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Balanced | Fosi Audio SK02 | Schiit Magni Heresy |
|---|---|---|
| Socket | 4.4mm | no separate rating |
| Power into 32Ω | 755 mW | — |
| Power into 300Ω | 80 mW derived | — |
| Output impedance | not published | — |
| Output noise | not published | — |
| Headphones it reaches 100 dB on out of 567 | 566 | — |
Only the Fosi Audio SK02 has a separate balanced rating from its maker; through it, it reaches 100 dB on 566 of the 567 models here. The Schiit Magni Heresy 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 | Fosi Audio SK02 | Schiit Magni Heresy |
|---|---|---|
| 32 Ω | Published | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Derived | Published |
| 600 Ω | Derived | Published |
Both makers publish a power rating. Fosi Audio SK02 publishes at 32 Ω; Schiit Magni Heresy 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 300 Ω and at 600 Ω only the Schiit Magni Heresy figure is the maker’s own. On those rows the derived number is the one to doubt first.
3 headphones reach 100 dB on the Schiit Magni Heresy but not on the Fosi Audio SK02 — Moondrop PARA, Symphonium Crimson, Symphonium Titan.
564 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: Schiit Magni Heresy has +26 dB of headroom there against +11 dB. 15 dB is about 29 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Schiit Magni Heresy because that maker publishes no output noise figure.
| Headphone | Impedance | Needs | Fosi Audio SK02 headroom | Schiit Magni Heresy headroom | Fosi Audio SK02 hiss | Schiit Magni Heresy hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +31 dB | +46 dB | 26 dB | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +11 dB | +26 dB | 6 dB | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +20 dB | +32 dB | 4 dB | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +16 dB | +29 dB | -1 dB | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +13 dB | +25 dB | -2 dB | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +9 dB | +22 dB | -7 dB | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +5 dB | +18 dB | -12 dB | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | +3 dB | +14 dB | -13 dB | not published |
The Fosi Audio SK02 costs $1 more than the Schiit Magni Heresy, and on these three axes the money buys nothing: among the 567 models here there is not one that the Fosi Audio SK02 handles and the Schiit Magni Heresy does not — not on power, not on the one-eighth rule, not on hiss. The traffic runs the other way: the cheaper Schiit Magni Heresy drives 3 models to 100 dB that the Fosi Audio SK02 does not.
Only published figures count here; blank axes are counted separately.
Each in full: Fosi Audio SK02 and Schiit Magni Heresy.