Short answer
Both are dongles, $66 against $69.
The iBasso DC03 Pro reaches 100 dB on 560 of the 567 models here, the ddHiFi TC35Pro (Mountain2) on 554.
| Specification | ddHiFi TC35Pro (Mountain2) | iBasso DC03 Pro |
|---|---|---|
| Power into 32Ω | 65 mW | 98 mW |
| Power into 150Ω | 14 mW | 21 mW |
| Power into 300Ω | 6.9 mW | 10 mW |
| Power into 600Ω | 3.5 mW | 5.2 mW |
| Output impedance | not published | 0.12 Ω |
| Output noise | not published | 0.9 µV |
| Price | $66 | $69 |
| Headphones it reaches 100 dB on out of 567 | 554 | 560 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Load | ddHiFi TC35Pro (Mountain2) | iBasso DC03 Pro |
|---|---|---|
| 32 Ω | Published | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Derived | Derived |
| 600 Ω | Derived | Derived |
Both makers publish a power rating. ddHiFi TC35Pro (Mountain2) publishes at 32 Ω; iBasso DC03 Pro at 32 Ω. The other rows are worked out from those.
The two publish at the same loads, which is the one case where the rows of this table can be read straight across.
6 headphones reach 100 dB on the iBasso DC03 Pro but not on the ddHiFi TC35Pro (Mountain2) — HiFiMAN HE-6se V2, HiFiMAN HE6 Remastered, HiFiMAN Susvara, 3 more.
554 of the 567 models here reach 100 dB on both.
Headroom is at a 100 dB SPL peak.
The widest gap on the list is the Sennheiser HD 600: iBasso DC03 Pro has +2 dB of headroom there against +0 dB. 2 dB is about 1.5 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for ddHiFi TC35Pro (Mountain2) because that maker publishes no output noise figure.
| Headphone | Impedance | Needs | ddHiFi TC35Pro (Mountain2) headroom | iBasso DC03 Pro headroom | ddHiFi TC35Pro (Mountain2) hiss | iBasso DC03 Pro hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +27 dB | +28 dB | not published | 14 dB |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +7 dB | +8 dB | not published | -6 dB |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +16 dB | +18 dB | not published | -8 dB |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +11 dB | +13 dB | not published | -13 dB |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +8 dB | +10 dB | not published | -14 dB |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +4 dB | +6 dB | not published | -20 dB |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +0 dB | +2 dB | not published | -24 dB |
| HiFiMAN Susvara | 60 Ω | 50 mW | -2 dB | +0 dB | not published | -26 dB |
The iBasso DC03 Pro costs $3 more than the ddHiFi TC35Pro (Mountain2). Out of the 567 models here, that difference buys 6 more models driven to 100 dB.
Nothing runs the other way: there is no axis here on which the cheaper of the two does better.
Only published figures count here; blank axes are counted separately.
Each in full: ddHiFi TC35Pro (Mountain2) and iBasso DC03 Pro.