Short answer
Both are portable players, $179 against $180.
The Surfans F28 reaches 100 dB on 561 of the 567 models here, the Hidizs AP80 Pro Max on 556.
| Specification | Hidizs AP80 Pro Max | Surfans F28 |
|---|---|---|
| Power into 32Ω | 70 mW | 125 mW |
| Power into 150Ω | 15 mW | 27 mW |
| Power into 300Ω | 7.5 mW | 13 mW |
| Power into 600Ω | 3.7 mW | 6.7 mW |
| Output impedance | not published | not published |
| Output noise | not published | not published |
| Price | $179 | $180 |
| Headphones it reaches 100 dB on out of 567 | 556 | 561 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Balanced | Hidizs AP80 Pro Max | Surfans F28 |
|---|---|---|
| Socket | 4.4mm | 4.4mm |
| Power into 32Ω | 190 mW | 450 mW |
| Power into 300Ω | 20 mW derived | 48 mW derived |
| Output impedance | not published | not published |
| Output noise | not published | not published |
| Headphones it reaches 100 dB on out of 567 | 564 | 566 |
Through the balanced sockets the Surfans F28 reaches 100 dB on 566 of the 567 models here and the Hidizs AP80 Pro Max on 564. Derived figures are worked out from the loads the maker did publish.
| Load | Hidizs AP80 Pro Max | Surfans F28 |
|---|---|---|
| 32 Ω | Published | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Derived | Derived |
| 600 Ω | Derived | Derived |
Both makers publish a power rating. Hidizs AP80 Pro Max publishes at 32 Ω; Surfans F28 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.
5 headphones reach 100 dB on the Surfans F28 but not on the Hidizs AP80 Pro Max — HiFiMAN Susvara, Moondrop PARA 2, Moondrop SKYLAND, 2 more.
556 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 Audio-Technica ATH-R70X: Surfans F28 has +7 dB of headroom there against +5 dB. 3 dB is about 1.8 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Hidizs AP80 Pro Max and Surfans F28 because neither maker publishes no output noise figure.
| Headphone | Impedance | Needs | Hidizs AP80 Pro Max headroom | Surfans F28 headroom | Hidizs AP80 Pro Max hiss | Surfans F28 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +27 dB | +29 dB | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +7 dB | +9 dB | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +16 dB | +19 dB | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +12 dB | +14 dB | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +8 dB | +11 dB | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +5 dB | +7 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +1 dB | +3 dB | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | -1 dB | +1 dB | not published | not published |
The Surfans F28 costs $1 more than the Hidizs AP80 Pro Max. Out of the 567 models here, that difference buys 5 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: Hidizs AP80 Pro Max and Surfans F28.