Short answer
Both are desktop DAC/amps, $199 against $219.
The SMSL C200 reaches 100 dB on 567 of the 567 models here, the Fosi Audio K7 on 566.
| Specification | Fosi Audio K7 | SMSL C200 |
|---|---|---|
| Power into 32Ω | 600 mW | 1.3 W |
| Power into 150Ω | 128 mW | 277 mW |
| Power into 300Ω | 64 mW | 139 mW |
| Power into 600Ω | 32 mW | 69 mW |
| Output impedance | not published | not published |
| Output noise | 2.5 µV | not published |
| Price | $199 | $219 |
| 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 | Fosi Audio K7 | SMSL C200 |
|---|---|---|
| Socket | 4.4mm | no separate rating |
| Power into 32Ω | 2.1 W | — |
| Power into 300Ω | 224 mW derived | — |
| Output impedance | not published | — |
| Output noise | 6.5 µV | — |
| Headphones it reaches 100 dB on out of 567 | 567 | — |
Only the Fosi Audio K7 has a separate balanced rating from its maker; through it, it reaches 100 dB on 567 of the 567 models here. The SMSL C200 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 K7 | SMSL C200 |
|---|---|---|
| 32 Ω | Published | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Derived | Derived |
| 600 Ω | Derived | Derived |
Both makers publish a power rating. Fosi Audio K7 publishes at 32 Ω; SMSL C200 at 32 Ω. The other rows are worked out from those.
The two publish at the same loads, which is the one case where the rows of this table can be read straight across.
1 headphone reaches 100 dB on the SMSL C200 but not on the Fosi Audio K7 — Symphonium Titan.
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 C200 has +26 dB of headroom there against +16 dB. 9 dB is about 8.7 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for SMSL C200 because that maker publishes no output noise figure.
| Headphone | Impedance | Needs | Fosi Audio K7 headroom | SMSL C200 headroom | Fosi Audio K7 hiss | SMSL C200 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +36 dB | +46 dB | 22 dB | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +16 dB | +26 dB | 2 dB | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +25 dB | +29 dB | 1 dB | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +21 dB | +24 dB | -4 dB | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +18 dB | +23 dB | -5 dB | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +14 dB | +17 dB | -11 dB | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +10 dB | +13 dB | -15 dB | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | +8 dB | +11 dB | -17 dB | not published |
The SMSL C200 costs $20 more than the Fosi Audio K7. Out of the 567 models here, that difference buys 1 more model driven to 100 dB.
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: Fosi Audio K7 and SMSL C200.