The Dan Clark Audio Expanse is 26Ω at 90.0 dB/mW; the Fostex T50RP MK3 is 50Ω at 92.0 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 Dan Clark Audio Expanse needs 2.0 dB more than the Fostex T50RP MK3 to reach the same loudness — 10 mW against 6.3 mW.
| Specification | Dan Clark Audio Expanse | Fostex T50RP MK3 |
|---|---|---|
| Impedance | 26 Ω | 50 Ω |
| Sensitivity | 90.0 dB/mW | 92.0 dB/mW |
| Sensitivity (voltage) | 105.9 dB/V | 105.0 dB/V |
| Power for 100 dB | 10 mW | 6.3 mW |
| Voltage for 100 dB | 0.51 V | 0.56 V |
| Current for 100 dB | 19.6 mA | 11.2 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 3.25 Ω | 6.25 Ω |
| Sources that reach 100 dB out of 280 | 279 | 280 |
1 of the 280 sources has the power for the Fostex T50RP MK3 but not for the Dan Clark Audio Expanse — Steinberg UR22C.
1 source is low enough in output impedance for the Fostex T50RP MK3 under the one-eighth rule but not for the Dan Clark Audio Expanse (Shanling H5).
279 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: Dan Clark Audio Expanse and Fostex T50RP MK3. Every figure on this page comes from what Dan Clark Audio and Fostex published, or is derived from it — what Dan Clark Audio publishes and what Fostex publishes, both counted.