Every amplifier, dongle and player on this site carries a power figure at 32, 150, 300 and 600 ohms. Almost no manufacturer publishes all four. This page explains exactly what was published, what was worked out, and what was thrown away — because a number you cannot trace is worth nothing, and a site that hides the difference is selling you something.
Of the 88 sources in the database, 46 have been traced back to a manufacturer document, and 42 are still carrying figures collected when the database was first assembled. Those 42 are being re-sourced one at a time, and until then their pages say so in plain words rather than quietly looking the same as the rest.
Published. The manufacturer states this power at this exact load. Nothing was done to it. 102 of the 379 figures in the database are this.
Derived. The manufacturer publishes a figure at some other load, and this one was worked out from it. The working is always the same, and it is the reason this site exists: an amplifier is a voltage source with a current limit, not a power source. So the conversion runs through voltage. A published figure of 180 mW into 32 ohms is √(0.180 × 32) = 2.40 volts; that voltage is then held between published loads, and held constant beyond the highest one. Holding voltage constant beyond the top published load understates what the amplifier can really do, because its voltage usually rises a little into a higher impedance. The error therefore runs in the safe direction: this site will tell you an amplifier is short of power before it tells you one is enough.
Upper bound. 7 sources publish a maximum output voltage and no power rating at any load at all — Qudelix, Astell&Kern and Tanchjim all do this. Voltage into a load can only ever be lower than voltage with nothing attached, so a power figure computed from it is a ceiling, not a rating. Those pages say upper bound on every line, and the real figure into a low impedance may be a good deal lower.
Through the output impedance. A few amplifiers — valve designs above all — publish one power figure and a high output impedance. For those the output impedance is not a footnote, it is the whole behaviour: it forms a voltage divider with the headphone, so the power an amplifier delivers peaks when the headphone impedance equals its own and falls away on both sides. The Bottlehead Crack, at a published 120 ohms, makes more power into 150 ohms than into either 32 or 600. That shape is computed from the two published numbers and nothing else.
A figure with no stated load is not a specification. Several well-known products publish exactly that — a bare wattage with nothing to attach it to — and they were left out rather than guessed at. So were products whose own documents contradict each other, and products whose figures could only be found on a dealer page that no two dealers agreed on.
| Product | Why it is not in the database |
|---|---|
| Apple USB-C to 3.5 mm Headphone Jack Adapter | Apple publishes no audio specs |
| Cayin HA-3A | power published per transformer tap range, no single load |
| Darkvoice 336SE | power published with no stated load |
| EPZ TP35 | no official product page any more |
| Feliks Audio Echo MkII | power published with no stated load |
| Feliks Audio Euforia | power published with no stated load |
| HiBy FC6 | power published with no stated load |
| Questyle M15C | only a 300 ohm figure, and questyle.com could not be reached |
| Quicksilver Headphone Amplifier | the maker's own page and manual disagree |
| Topping A70 Pro | dealer tables disagree (10,000 vs 12,600 mW into 16 ohm) |
| Topping L70 | only a 16 ohm figure published; dealers disagree |
| Woo Audio WA7 Fireflies (3rd gen) | published figure (1.5 W into 4 ohm) is unusable |
Some of these will come back if the manufacturer publishes a load alongside the number, or if a factory document turns up that settles a conflict. None of them will come back as an estimate.
11 sources have no published output impedance, and 23 have no published noise figure. On those pages the damping check and the hiss estimate are not run at all. It would have been easy to substitute a typical value and let every page look complete; the page says the number does not exist instead.
The other honest limitation is that a manufacturer's own figure is a claim, not a measurement. Where a maker quotes power at 1% distortion, that is a louder number than the same amplifier at 0.1%, and this site records the distortion condition where one was printed. Independent measurements exist and are better than any of this — they are just not something this site can reproduce.
If you find a figure here that disagrees with a manufacturer document, the document wins. The page footer has the contact address.