The Moondrop Aria is 32Ω at 107.1 dB/mW; the Truthear Zero:RED is 17.5Ω at 99.9 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 Truthear Zero:RED needs 7.2 dB more than the Moondrop Aria to reach the same loudness — 1.0 mW against 0.19 mW.
| Specification | Moondrop Aria | Truthear Zero:RED |
|---|---|---|
| Impedance | 32 Ω | 17.5 Ω |
| Sensitivity | 107.1 dB/mW | 99.9 dB/mW |
| Sensitivity (voltage) | 122.0 dB/V | 117.5 dB/V |
| Power for 100 dB | 0.19 mW | 1.0 mW |
| Voltage for 100 dB | 79 mV | 0.13 V |
| Current for 100 dB | 2.5 mA | 7.6 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 4.00 Ω | 2.19 Ω |
| Sources that reach 100 dB out of 280 | 280 | 280 |
Every source in the database that drives one of them drives the other. On power, the choice between these two changes nothing about what amplifier you need.
2 sources stay below the audible-hiss threshold with the Truthear Zero:RED but cross it with the Moondrop Aria (FiiO BTR11, Rupert Neve RNHP).
280 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 Aria and Truthear Zero:RED. Every figure on this page comes from what Moondrop and Truthear published, or is derived from it — what Moondrop publishes and what Truthear publishes, both counted.