Both are dongles, $160 against $139. 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 Hidizs S9 Pro Plus reaches 100 dB on 562 of the 567 models here, the ddHiFi TC44Grip on 557.
| Specification | ddHiFi TC44Grip | Hidizs S9 Pro Plus |
|---|---|---|
| Power into 32Ω | 80 mW | 138 mW |
| Power into 150Ω | 17 mW | 29 mW |
| Power into 300Ω | 8.5 mW | 15 mW |
| Power into 600Ω | 4.3 mW | 7.4 mW |
| Output impedance | not published | not published |
| Output noise | not published | not published |
| Price | $160 | $139 |
| Headphones it reaches 100 dB on out of 567 | 557 | 562 |
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.
5 headphones reach 100 dB on the Hidizs S9 Pro Plus but not on the ddHiFi TC44Grip — HiFiMAN Susvara, Moondrop PARA 2, Moondrop VENUS, 2 more.
557 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: ddHiFi TC44Grip and Hidizs S9 Pro Plus. Or put either against your own headphones in the source comparison tool.