The Moondrop COSMO is 15Ω at 81.8 dB/mW; the Moondrop Stellaris is 36Ω at 102.6 dB/mW. This page is only about what they ask of an amplifier — not how they sound, which no specification on either sheet can tell you.
The COSMO needs 20.8 dB more than the Stellaris to reach the same loudness — 66 mW against 0.55 mW.
| Specification | COSMO | Stellaris |
|---|---|---|
| Impedance | 15 Ω | 36 Ω |
| Sensitivity | 81.8 dB/mW | 102.6 dB/mW |
| Sensitivity (voltage) | 100.0 dB/V | 117.0 dB/V |
| Power for 100 dB | 66 mW | 0.55 mW |
| Voltage for 100 dB | 1.00 V | 0.14 V |
| Current for 100 dB | 66.4 mA | 3.9 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 1.88 Ω | 4.50 Ω |
| Sources that reach 100 dB out of 280 | 188 | 280 |
92 of the 280 sources have the power for the Stellaris but not for the COSMO — Apple USB-C dongle (US), Apple USB-C dongle (EU), Generic CX31993 dongles, 89 more.
3 sources are low enough in output impedance for the Stellaris under the one-eighth rule but not for the COSMO (Astell&Kern HC3, RME Fireface UFX II, RME Fireface UFX III).
188 of the 280 sources here reach 100 dB on both. That count is about power only — the output-impedance and hiss lines above are separate questions, and a source can pass this one and fail those.
Each model has a page of its own with the full source list, the hiss estimate and the provenance of every figure above: Moondrop COSMO and Moondrop Stellaris. Every figure on this page comes from what Moondrop published, or is derived from it — what that maker publishes, counted.