Both are desktop amplifiers, $1995 against $2995. 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 HeadAmp GS-X mk2 reaches 100 dB on 567 of the 567 models here, the Ferrum OOR on 566.
| Specification | Ferrum OOR | HeadAmp GS-X mk2 |
|---|---|---|
| Power into 32Ω | 1.1 W | 7.1 W |
| Power into 150Ω | 800 mW | 2.0 W |
| Power into 300Ω | 400 mW | 1.0 W |
| Power into 600Ω | 200 mW | 500 mW |
| Output impedance | 0.3 Ω | not published |
| Output noise | 1.5 µV unverified | not published |
| Price | $1995 | $2995 |
| Headphones it reaches 100 dB on out of 567 | 566 | 567 |
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 | Ferrum OOR | HeadAmp GS-X mk2 |
|---|---|---|
| 32 Ω | Derived | Derived |
| 150 Ω | Derived | Derived |
| 300 Ω | Published | Derived |
| 600 Ω | Derived | Derived |
Only one of these two columns starts from a power rating. Ferrum OOR publishes one at 300 Ω; HeadAmp GS-X mk2 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 HeadAmp GS-X mk2 understates rather than flatters — but at 300 Ω is the only load here at which its maker can be held to a figure.
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 HeadAmp GS-X mk2 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 Shure SE846: HeadAmp GS-X mk2 has +49 dB of headroom there against +39 dB. 10 dB is about 9.6 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Ferrum OOR and HeadAmp GS-X mk2 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 | Ferrum OOR headroom | HeadAmp GS-X mk2 headroom | Ferrum OOR hiss | HeadAmp GS-X mk2 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +39 dB | +49 dB | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +19 dB | +29 dB | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +33 dB | +37 dB | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +29 dB | +33 dB | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +20 dB | +30 dB | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +22 dB | +26 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +18 dB | +22 dB | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | +16 dB | +20 dB | not published | not published |
The HeadAmp GS-X mk2 costs $1000 more than the Ferrum OOR. Out of the 567 models here, that difference buys 1 more model driven to 100 dB.
Nothing runs the other way: there is no axis here on which the cheaper of the two does better.
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: Ferrum OOR and HeadAmp GS-X mk2. Or put either against your own headphones in the source comparison tool.