Short answer
Both are dongles, $76 against $99.
The ddHiFi TC44 Pro E2 reaches 100 dB on 565 of the 567 models here, the ddHiFi TC35Pro (Eye2) on 554.
| Specification | ddHiFi TC35Pro (Eye2) | ddHiFi TC44 Pro E2 |
|---|---|---|
| Power into 32Ω | 65 mW | 250 mW |
| Power into 150Ω | 14 mW | 53 mW |
| Power into 300Ω | 6.9 mW | 27 mW |
| Power into 600Ω | 3.5 mW | 13 mW |
| Output impedance | not published | not published |
| Output noise | not published | not published |
| Price | $76 | $99 |
| Headphones it reaches 100 dB on out of 567 | 554 | 565 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Load | ddHiFi TC35Pro (Eye2) | ddHiFi TC44 Pro E2 |
|---|---|---|
| 32 Ω | Published | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Derived | Derived |
| 600 Ω | Derived | Derived |
Both makers publish a power rating. ddHiFi TC35Pro (Eye2) publishes at 32 Ω; ddHiFi TC44 Pro E2 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.
11 headphones reach 100 dB on the ddHiFi TC44 Pro E2 but not on the ddHiFi TC35Pro (Eye2) — HiFiMAN HE-6se V2, HiFiMAN HE6 Remastered, HiFiMAN Susvara, 8 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: ddHiFi TC44 Pro E2 has +6 dB of headroom there against +0 dB. 6 dB is about 3.9 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for ddHiFi TC35Pro (Eye2) and ddHiFi TC44 Pro E2 because neither maker publishes no output noise figure.
| Headphone | Impedance | Needs | ddHiFi TC35Pro (Eye2) headroom | ddHiFi TC44 Pro E2 headroom | ddHiFi TC35Pro (Eye2) hiss | ddHiFi TC44 Pro E2 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +27 dB | +32 dB | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +7 dB | +12 dB | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +16 dB | +22 dB | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +11 dB | +17 dB | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +8 dB | +14 dB | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +4 dB | +10 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +0 dB | +6 dB | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | -2 dB | +4 dB | not published | not published |
The ddHiFi TC44 Pro E2 costs $23 more than the ddHiFi TC35Pro (Eye2). Out of the 567 models here, that difference buys 11 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 (Eye2) and ddHiFi TC44 Pro E2.