Short answer
Both are desktop amplifiers, $150 against $169.
The xDuoo MT-604 reaches 100 dB on 567 of the 567 models here, the PreSonus HP4 on 558.
| Specification | PreSonus HP4 | xDuoo MT-604 |
|---|---|---|
| Power into 32Ω | 69 mW | 2.0 W |
| Power into 150Ω | 52 mW | 427 mW |
| Power into 300Ω | 26 mW | 213 mW |
| Power into 600Ω | 13 mW | 107 mW |
| Output impedance | not published | not published |
| Output noise | not published | not published |
| Price | $150 | $169 |
| Headphones it reaches 100 dB on out of 567 | 558 | 567 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Load | PreSonus HP4 | xDuoo MT-604 |
|---|---|---|
| 32 Ω | Derived | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Derived | Derived |
| 600 Ω | Derived | Derived |
Only one of these two columns starts from a power rating. xDuoo MT-604 publishes one at 32 Ω; PreSonus HP4 publishes none at any of these four loads, so its column is worked out from power it published at other loads. Both are arithmetic on a maker’s own figures rather than guesses, and the method used for the PreSonus HP4 understates rather than flatters — but at 32 Ω is the only load here at which its maker can be held to a figure.
9 headphones reach 100 dB on the xDuoo MT-604 but not on the PreSonus HP4 — Moondrop COSMO, Moondrop PARA, Moondrop PARA 2, 6 more.
558 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 HiFiMAN HE400se: xDuoo MT-604 has +23 dB of headroom there against +8 dB. 15 dB is about 29 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for PreSonus HP4 and xDuoo MT-604 because neither maker publishes no output noise figure.
| Headphone | Impedance | Needs | PreSonus HP4 headroom | xDuoo MT-604 headroom | PreSonus HP4 hiss | xDuoo MT-604 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +27 dB | +42 dB | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +7 dB | +22 dB | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +21 dB | +31 dB | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +17 dB | +26 dB | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +8 dB | +23 dB | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +10 dB | +19 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +6 dB | +15 dB | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | +4 dB | +13 dB | not published | not published |
The xDuoo MT-604 costs $19 more than the PreSonus HP4. Out of the 567 models here, that difference buys 9 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: PreSonus HP4 and xDuoo MT-604.