Both are desktop amplifiers, $1800 against $1995. 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?
The Cayin HA-6A reaches 100 dB on 567 of the 567 models here, the Ferrum OOR on 566.
| Specification | Cayin HA-6A | Ferrum OOR |
|---|---|---|
| Power into 32Ω | 3.0 W | 1.1 W |
| Power into 150Ω | 1.5 W | 800 mW |
| Power into 300Ω | 900 mW | 400 mW |
| Power into 600Ω | 450 mW | 200 mW |
| Output impedance | 2 Ω unverified | 0.3 Ω |
| Output noise | 25 µV unverified | 1.5 µV unverified |
| Price | $1800 | $1995 |
| Headphones it reaches 100 dB on out of 567 | 567 | 566 |
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 | Cayin HA-6A | Ferrum OOR |
|---|---|---|
| 32 Ω | Unverified | Derived |
| 150 Ω | Unverified | Derived |
| 300 Ω | Unverified | Published |
| 600 Ω | Unverified | Derived |
Cayin HA-6A publishes no electrical specification at all. That is true of 10 of the 280 sources here, and the figures in that column come from independent measurement rather than from a maker document — which is not worse, but it is not the same thing, and it cannot be checked against anything the maker will stand behind.
The Ferrum OOR column does stand on a power rating its maker printed, at one of these four loads at least. Reading the two straight across sets one kind of claim against another, and nobody has written down the conditions of both side by side.
What each of these labels means, and why a derived figure is still worth printing, is set out in how this data was built.
1 headphone reaches 100 dB on the Cayin HA-6A but not on the Ferrum OOR — Symphonium Titan.
566 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 Campfire Audio Andromeda 2020: Cayin HA-6A has +23 dB of headroom there against +19 dB. 4 dB is about 2.8 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Cayin HA-6A and Ferrum OOR 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 | Cayin HA-6A headroom | Ferrum OOR headroom | Cayin HA-6A hiss | Ferrum OOR hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +43 dB | +39 dB | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +23 dB | +19 dB | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +34 dB | +33 dB | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +32 dB | +29 dB | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +25 dB | +20 dB | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +26 dB | +22 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +21 dB | +18 dB | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | +16 dB | +16 dB | not published | not published |
The Ferrum OOR costs $195 more than the Cayin HA-6A, and on these three axes the money buys nothing: among the 567 models here there is not one that the Ferrum OOR handles and the Cayin HA-6A does not — not on power, not on the one-eighth rule, not on hiss. The traffic runs the other way: the cheaper Cayin HA-6A drives one model to 100 dB that the Ferrum OOR 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 a full headphone list and the provenance of every figure — worth opening here, because Cayin HA-6A has published no electrical specification at all and everything above comes from independent measurement: Cayin HA-6A and Ferrum OOR. Or put either against your own headphones in the source comparison tool.