Short answer
Both are dongles, $210 against $149.
The FiiO KA17 reaches 100 dB on 564 of the 567 models here, the EPZ TP50 on 561.
| Specification | EPZ TP50 | FiiO KA17 |
|---|---|---|
| Power into 32Ω | 121 mW | 140 mW |
| Power into 150Ω | 26 mW | 34 mW |
| Power into 300Ω | 13 mW | 20 mW |
| Power into 600Ω | 6.5 mW | 10.0 mW |
| Output impedance | not published | 1.0 Ω |
| Output noise | 1.0 µV | 2.0 µV |
| Price | $210 | $149 |
| Headphones it reaches 100 dB on out of 567 | 561 | 564 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Balanced | EPZ TP50 | FiiO KA17 |
|---|---|---|
| Socket | 4.4mm | 4.4mm |
| Power into 32Ω | 240 mW | 300 mW |
| Power into 300Ω | 26 mW derived | 30 mW |
| Output impedance | not published | 1.5 Ω |
| Output noise | 1.0 µV | 2.2 µV |
| Headphones it reaches 100 dB on out of 567 | 565 | 565 |
Through the balanced sockets the two are level on the same test: each reaches 100 dB on 565 of the 567 models here. Derived figures are worked out from the loads the maker did publish.
| Load | EPZ TP50 | FiiO KA17 |
|---|---|---|
| 32 Ω | Published | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Derived | Published |
| 600 Ω | Derived | Derived |
Both makers publish a power rating. EPZ TP50 publishes at 32 Ω; FiiO KA17 at 32 Ω and at 300 Ω. The other rows are worked out from those.
So the two columns are not equally firm row by row: at 300 Ω only the FiiO KA17 figure is the maker’s own. On those rows the derived number is the one to doubt first.
3 headphones reach 100 dB on the FiiO KA17 but not on the EPZ TP50 — Moondrop COSMO, Symphonium Helios, Symphonium Zenith.
5 headphones stay below the audible-hiss threshold on the EPZ TP50 but cross it on the FiiO KA17 (64 Audio Fourte, Campfire Audio Clara, Shure SE846, 2 more).
561 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 Shure SE846: FiiO KA17 has +32 dB of headroom there against +29 dB. 3 dB is about 1.8 times the power, which matters for peaks rather than for how loud the music sits.
Hiss below about 20 dB SPL is inaudible in a quiet room.
| Headphone | Impedance | Needs | EPZ TP50 headroom | FiiO KA17 headroom | EPZ TP50 hiss | FiiO KA17 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +29 dB | +32 dB | 14 dB | 20 dB |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +9 dB | +12 dB | -6 dB | 0 dB |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +18 dB | +19 dB | -7 dB | -1 dB |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +14 dB | +16 dB | -12 dB | -6 dB |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +11 dB | +12 dB | -13 dB | -7 dB |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +7 dB | +9 dB | -19 dB | -13 dB |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +3 dB | +5 dB | -23 dB | -17 dB |
| HiFiMAN Susvara | 60 Ω | 50 mW | +1 dB | +2 dB | -25 dB | -19 dB |
The EPZ TP50 costs $61 more than the FiiO KA17. Out of the 567 models here, that difference buys 5 more models kept below the audible-hiss threshold.
It does not run one way only: the cheaper FiiO KA17 drives 3 models to 100 dB that the EPZ TP50 does not, which is the part worth checking against your own headphones before paying the difference.
Only published figures count here; blank axes are counted separately.