The Truthear PURE is 13.8Ω at 105.4 dB/mW; the Truthear Zero is 10Ω at 97.5 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 Zero needs 7.9 dB more than the PURE to reach the same loudness — 1.8 mW against 0.29 mW.
| Specification | PURE | Zero |
|---|---|---|
| Impedance | 13.8 Ω | 10 Ω |
| Sensitivity | 105.4 dB/mW | 97.5 dB/mW |
| Sensitivity (voltage) | 124.0 dB/V | 117.5 dB/V |
| Power for 100 dB | 0.29 mW | 1.8 mW |
| Voltage for 100 dB | 63 mV | 0.13 V |
| Current for 100 dB | 4.6 mA | 13.3 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 1.73 Ω | 1.25 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.
4 sources are low enough in output impedance for the PURE under the one-eighth rule but not for the Zero (FiiO KA13, FiiO M11S, Singxer SA-1, 1 more).
4 sources stay below the audible-hiss threshold with the Zero but cross it with the PURE (FiiO BTR11, FiiO K11 R2R, Lake People G111 Mk II, 1 more).
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: Truthear PURE and Truthear Zero. Every figure on this page comes from what Truthear published, or is derived from it — what that maker publishes, counted.