Short answer
Both are desktop DAC/amps, $3500 against $3799.
The Naim Uniti Atom Headphone Edition reaches 100 dB on 567 of the 567 models here, the Marantz SACD 30n on 552.
| Specification | Marantz SACD 30n | Naim Uniti Atom Headphone Edition |
|---|---|---|
| Power into 32Ω | 50 mW | 750 mW |
| Power into 150Ω | 11 mW | 160 mW |
| Power into 300Ω | 5.3 mW | 80 mW |
| Power into 600Ω | 2.7 mW | 40 mW |
| Output impedance | not published | not published |
| Output noise | not published | not published |
| Price | $3500 | $3799 |
| Headphones it reaches 100 dB on out of 567 | 552 | 567 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Load | Marantz SACD 30n | Naim Uniti Atom Headphone Edition |
|---|---|---|
| 32 Ω | Published | Derived |
| 150 Ω | Derived | Derived |
| 300 Ω | Derived | Derived |
| 600 Ω | Derived | Derived |
Only one of these two columns starts from a power rating. Marantz SACD 30n publishes one at 32 Ω; Naim Uniti Atom Headphone Edition 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 Naim Uniti Atom Headphone Edition understates rather than flatters — but at 32 Ω is the only load here at which its maker can be held to a figure.
15 headphones reach 100 dB on the Naim Uniti Atom Headphone Edition but not on the Marantz SACD 30n — HiFiMAN HE-6se V2, HiFiMAN HE6 Remastered, HiFiMAN Susvara, 12 more.
552 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 Campfire Audio Andromeda 2020: Naim Uniti Atom Headphone Edition has +23 dB of headroom there against +5 dB. 18 dB is about 60 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Marantz SACD 30n and Naim Uniti Atom Headphone Edition because neither maker publishes no output noise figure.
| Headphone | Impedance | Needs | Marantz SACD 30n headroom | Naim Uniti Atom Headphone Edition headroom | Marantz SACD 30n hiss | Naim Uniti Atom Headphone Edition hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +25 dB | +43 dB | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +5 dB | +23 dB | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +15 dB | +26 dB | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +10 dB | +22 dB | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +7 dB | +21 dB | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +3 dB | +15 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | -1 dB | +11 dB | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | -3 dB | +9 dB | not published | not published |
The Naim Uniti Atom Headphone Edition costs $299 more than the Marantz SACD 30n. Out of the 567 models here, that difference buys 15 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: Marantz SACD 30n and Naim Uniti Atom Headphone Edition.