Both are portable players, $800 against $649. This page puts them side by side on the only three things a maker can be held to — power, output impedance and noise — and then asks the question that actually matters: which headphones do they treat differently?
On raw power they are level: each reaches 100 dB on 565 of the 567 non-electrostatic models here.
| Specification | Astell&Kern SR35 | Cayin N3 Ultra |
|---|---|---|
| Power into 32Ω | 300 mW | 250 mW |
| Power into 150Ω | 64 mW | 53 mW |
| Power into 300Ω | 32 mW | 27 mW |
| Power into 600Ω | 16 mW | 13 mW |
| Output impedance | 1.1 Ω | 0.5 Ω |
| Output noise | 4 µV unverified | not published |
| Price | $800 | $649 |
| Headphones it reaches 100 dB on out of 567 | 565 | 565 |
A figure marked not published is missing from the maker’s own material, which is not the same as being good or bad. Where one of these two publishes a number and the other does not, the comparison on that axis cannot be made at all — and saying so is more useful than guessing.
| Load | Astell&Kern SR35 | Cayin N3 Ultra |
|---|---|---|
| 32 Ω | Upper bound | Published |
| 150 Ω | Upper bound | Derived |
| 300 Ω | Upper bound | Derived |
| 600 Ω | Upper bound | Derived |
These two columns are not the same kind of number, and that matters more than the gap between them. Cayin N3 Ultra publishes a power rating (at 32 Ω); Astell&Kern SR35 publishes no power figure at any load, only a maximum output voltage, so every milliwatt in its column is a ceiling worked out from that voltage.
A ceiling assumes the amplifier holds that voltage into the load, and nothing on Astell&Kern SR35’s own sheet says it does. It is the most flattering reading available, and it is used here only because the alternative is a blank. Where the Astell&Kern SR35 column looks the stronger of the two, treat the difference as unproven rather than measured. 24 of the 280 sources here are in that position, with no published power rating at any load.
What each of these labels means, and why a derived figure is still worth printing, is set out in how this data was built.
On power they are interchangeable across this whole database: there is no headphone here that one reaches 100 dB on and the other does not.
27 headphones are left alone by the Cayin N3 Ultra under the one-eighth rule but coloured by the Astell&Kern SR35 (64 Audio Nio, 64 Audio U18s, 64 Audio Volur, 24 more).
565 of the 567 models here reach 100 dB on both. That is a power count and nothing more; whether either source suits a given headphone also depends on the two lines above.
The counts above say how many models the two treat differently. This says by how much. The same 8 headphones appear on every page of this kind, ordered from the easiest to drive to the hardest, so a row can be read across pages as well as across columns. Headroom is at a 100 dB SPL peak.
The widest gap on the list is the Audeze LCD-2 Classic: Astell&Kern SR35 has +22 dB of headroom there against +22 dB. 1 dB is about 1.2 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Astell&Kern SR35 and Cayin N3 Ultra because neither maker publishes no output noise figure. That is a gap in the specification, not a quiet amplifier, and it is left blank here rather than filled with a plausible number.
| Headphone | Impedance | Needs | Astell&Kern SR35 headroom | Cayin N3 Ultra headroom | Astell&Kern SR35 hiss | Cayin N3 Ultra hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +33 dB | +32 dB | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +13 dB | +12 dB | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +22 dB | +22 dB | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +18 dB | +17 dB | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +15 dB | +14 dB | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +11 dB | +10 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +7 dB | +6 dB | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | +5 dB | +4 dB | not published | not published |
The Astell&Kern SR35 costs $151 more than the Cayin N3 Ultra, and on these three axes the money buys nothing: among the 567 models here there is not one that the Astell&Kern SR35 handles and the Cayin N3 Ultra does not — not on power, not on the one-eighth rule, not on hiss. The traffic runs the other way: the cheaper Cayin N3 Ultra leaves 27 models alone under the one-eighth rule that the Astell&Kern SR35 does not.
Everything in this paragraph counts only figures the two makers published. An advantage on an axis one of them leaves blank cannot be counted, and is not counted — how often that happens is its own page.
Each has a page of its own with every power figure traced to what the maker published and a full headphone list: Astell&Kern SR35 and Cayin N3 Ultra. Or put either against your own headphones in the source comparison tool.