This database holds 156 sources. Getting there meant reading 204 spec sheets, because 48 products were checked and then left out — not because they are bad, but because their makers never published a number this site could honestly use. What follows is what that reading turned up.
A headphone amplifier has one job that can be written down: deliver so many milliwatts into so many ohms. That is two numbers. A surprising share of the industry publishes one of them, or neither, or publishes a third number that looks like power and is not.
There are 741 power figures across the database, one per source per load. Each one is labelled, and the labels are not decoration — they are the difference between a manufacturer's claim and this site's arithmetic.
| Status | Figures | What it means |
|---|---|---|
| Published at that exact load | 306 | the maker printed this power, into this impedance |
| Between two published loads | 94 | output voltage interpolated between the two figures either side |
| Beyond the published loads | 190 | output voltage held at its last published value, which understates rather than flatters |
| From a maximum voltage only | 96 | the maker published a voltage and no power, so this is a ceiling, not a rating |
| From one load plus output impedance | 11 | the voltage-divider model, which is the right one for a high-impedance output |
| Not yet traced to a document | 44 | carried over from the material this database was first assembled from |
41% of the figures here are the manufacturer's own, at the manufacturer's own load. The rest are derived, and every one of them is derived by holding output voltage constant rather than power, because that is what an amplifier actually does as the load changes. The method is written up in full.
| Reason | Products |
|---|---|
| the product page or the whole product is gone | 12 |
| the maker publishes no headphone specification at all | 12 |
| a power figure with no load attached to it | 6 |
| the maker's own numbers disagree with each other | 5 |
| only one load, and too high to work down from | 4 |
| the specification is published only as a picture | 3 |
| other | 3 |
| the product has no headphone output | 3 |
The largest group is not incompetence, it is time: product pages come down, distributors change, and a five-year-old amplifier can lose its specification entirely. The second largest is more interesting. 12 manufacturers, several of them large, publish a headphone output with no electrical description of it whatsoever — the jack appears in the connector list and nowhere else.
Audient's interface spec sheets print three numbers on one line: a peak voltage, an RMS voltage, and a power. On the iD4 MkII at 30 ohms those are 2.59 V peak, 1.827 Vrms and 223 mW. But 1.827 Vrms into 30 ohms is 111 mW. 2.59 V into 30 ohms is 223.6 mW — which is exactly what they printed. The relation holds on all nine published points across the iD4 MkII, iD24 and EVO 4. Audient's published headphone power is consistently twice the real figure, and the voltages printed beside it are correct. This database uses half of each printed value and says so on every affected page.
The G111 Mk II datasheet prints load, dBu, volts and milliwatts in four columns. On three of its six rows the milliwatt column does not match the volt column: 300 ohms is printed as 1050 mW where 16.5 V implies 908 mW, 50 ohms as 2050 mW where 9.2 V implies 1693 mW, 32 ohms as 1400 mW where 6.2 V implies 1201 mW. The dBu column agrees with the volts on every row, so the volts are self-consistent and the milliwatts are the odd column out. The same table appears in three separate official PDFs. This site records what Lake People printed and flags the gap rather than quietly picking a side.
Apogee gives “15 dBu / 240 mW @ 32 ohms”. 15 dBu is 4.36 Vrms, which into 32 ohms is 593 mW. 240 mW into 32 ohms is 2.77 Vrms, which is 11.1 dBu. One of those two numbers is wrong and Apogee does not say which, so both are recorded as printed.
Balanced outputs are usually sold as the powerful ones. SPL publishes the opposite for the Phonitor xe: 5 W into 250 ohms single-ended against 3.5 W balanced, and 2.7 W against 0.7 W at 32 ohms — along with a higher source impedance and a higher noise floor on the balanced jack. It is published clearly and it is worth reading before assuming the four-pin socket is the better one.
34 of the 156 sources here publish no output impedance at all, and 75 publish no noise figure. That matters more than it sounds: output impedance is what decides whether a source will tilt the frequency response of a multi-driver in-ear, and it is a single number that costs nothing to measure.
Where it is published, the spread is enormous. Merging's Anubis states 0.035 ohms. Focusrite's Scarlett Solo and 2i2 (4th gen) state 50 ohms, and the ART HeadAmp 4 Pro 47 ohms — both of which fail the one-eighth rule against almost any headphone you could plug into them, and neither of which is hiding it. The rule, and what it does to your headphones, is here.
Reading spec sheets carefully means reading which section a number sits in. Steinberg's IXO22 manual prints “Output Impedance 150 Ω” — in the line output section; Steinberg publishes no headphone output impedance. PreSonus prints “Impedance Working Range: 32 Ω to 300 Ω”, which is the recommended load, not the source impedance. Behringer's U-PHORIA datasheet prints a maximum output level that belongs to the main outputs; the word “Phones” appears only as a connector type. All three are easy to copy into a database as headphone specifications, and all three would be wrong.
A published power figure is only as good as the load printed next to it. If a spec sheet says “1 W output” with no impedance, it has told you nothing: 1 W into 16 ohms and 1 W into 600 ohms are different amplifiers. If it gives a voltage and no power, you have a ceiling rather than a rating, and the real figure into a low impedance may be far below it.
Every source page here says which of its numbers came from the manufacturer and which this site worked out, load by load. Browse them all, or download the lot with the provenance column intact.