Both are dongles, $139 against $140. This page puts them side by side on the only three things a maker can be held to — power, output impedance and noise — and then asks the question that actually matters: which headphones do they treat differently?
The Tanchjim LUNA reaches 100 dB on 565 of the 567 models here, the Hidizs S9 Pro Plus on 562.
| Specification | Hidizs S9 Pro Plus | Tanchjim LUNA |
|---|---|---|
| Power into 32Ω | 138 mW | 285 mW |
| Power into 150Ω | 29 mW | 80 mW |
| Power into 300Ω | 15 mW | 54 mW |
| Power into 600Ω | 7.4 mW | 27 mW |
| Output impedance | not published | not published |
| Output noise | not published | 1.3 µV |
| Price | $139 | $140 |
| Headphones it reaches 100 dB on out of 567 | 562 | 565 |
A figure marked not published is missing from the maker’s own material, which is not the same as being good or bad. Where one of these two publishes a number and the other does not, the comparison on that axis cannot be made at all — and saying so is more useful than guessing.
3 headphones reach 100 dB on the Tanchjim LUNA but not on the Hidizs S9 Pro Plus — Moondrop COSMO, Symphonium Crimson, Symphonium Helios.
562 of the 567 models here reach 100 dB on both. That is a power count and nothing more; whether either source suits a given headphone also depends on the two lines above.
Each has a page of its own with every power figure traced to what the maker published and a full headphone list: Hidizs S9 Pro Plus and Tanchjim LUNA. Or put either against your own headphones in the source comparison tool.