Usually yes, and by a wider margin than the forums suggest. Half the USB-C dongles in this database sit between 8 and 17 mW into 300Ω, and the Sennheiser HD 600 needs 6.6 mW and 1.41 V for a 100 dB peak, which is louder than almost anyone listens. Of the 280 sources here, 261 manage it. The exceptions are the weakest adapters — Apple's US dongle manages about 3 mW into 300Ω — and a 3.5 mm socket built into a phone, which is usually weaker than a dongle. The calculator shows what your own pair needs.
Far less than the marketing implies. Across the 567 non-electrostatic models here, the median need at 100 dB SPL is about 1 mW, 279 models need under a milliwatt, and 93% of them need under ten. The handful that genuinely need hundreds of milliwatts are low-sensitivity planars and a few in-ears with very low impedance. 100 dB is the reference used here because it leaves headroom above normal listening for the loud moments in music — it is not a volume anyone should sit at.
The number on its own tells you almost nothing, because it is only meaningful next to a load. Two watts into 32Ω and two watts into 300Ω are completely different amplifiers: the first needs current, the second needs voltage swing, and most portable gear runs out of voltage long before it runs out of watts. That is why every source page here gives power at 32, 150, 300 and 600Ω rather than one headline figure, and says for each load whether the maker published it or the site derived it.
On the published number, no. HiFiMAN prints 83 dB, and if that is per milliwatt the Susvara needs 50 mW for a 100 dB peak — 231 of the 280 sources here can do that. The catch is that HiFiMAN never states what the 83 dB is referenced to. If it is per volt, the real figure at 60Ω is about 70.8 dB/mW and almost nothing on this site would drive it. The “needs a speaker amp” reputation is built on a number whose unit its own maker has never published. The audit goes through this.
It matters for low-impedance headphones, which is most of them: 63% of the models here are 32Ω or below. The rule of thumb is that the source should be under an eighth of the headphone's impedance, because above that the amplifier's own impedance starts shaping the frequency response of any headphone whose impedance varies with frequency. Of the 192 sources here that publish a figure, 50 are above 1Ω and 34 are at 8Ω or more — the Bottlehead Crack (OTL kit) is 120Ω. The impedance interaction tool puts a number on it for your own pair.
Often, and it is the half of amplifier matching nobody calculates. Hiss is the source's own noise floor played through a headphone efficient enough to make it audible, so it depends on both. The awkward part is the data: only 115 of the 280 sources here publish a noise figure at all, so for the rest there is nothing to calculate from and this site says so rather than guessing. The hiss calculator works it out where the number exists.
For power, sometimes: a balanced stage that doubles the voltage swing gives four times the power, which is 6 dB. 124 of the sources here publish a separate balanced rating, and where they do, that rating is on the product's page. But plenty of products feed a balanced jack from the same single-ended amplifier and publish one figure for both, and then the 4.4 mm socket buys you nothing but a different plug. The rest of what balanced does — common-mode noise rejection — is real but rarely audible on a desk. The balanced calculator shows the difference where there is one.
Beyond a basic quality threshold, rarely. Modern DAC chips are extremely good. In level-matched blind tests, listeners generally cannot tell competent DACs apart at all. What does separate them is measurable and useful: output power, output impedance, noise floor, and features. Amplifier capability and headphone choice decide what you actually hear.
Treat it as an indication rather than a specification, because it can mean two things that are 1.41 V apart in practice. Sensitivity is quoted either per milliwatt or per volt, and the two differ by 10 × log10(1000/Z) — about 5 dB on a 300Ω headphone and 15 to 18 dB on an in-ear. 142 models here print a bare decibel figure with no reference anywhere. Their pages show both readings and say which one is on the table. The converter does the arithmetic.
For critical listening: Beyerdynamic DT 770 Pro (closed) or DT 990 Pro (open). For casual listening: Audio-Technica ATH-M50X. All three are used daily in professional environments. None of them require you to spend more to enjoy them.
Tube amplifiers usually measure with more second-harmonic distortion, though at normal listening levels that is generally below the threshold at which anyone can hear it on music. The effect that is reliably audible is a different one: most tube amps have a high output impedance, and that changes the frequency response of any headphone whose impedance varies with frequency — often by more than an EQ preset would. The impedance interaction tool shows the size of it for your own pair. If you want the recording as it was made, a low-impedance solid-state amp is the safer choice. If you want music to sound a certain way regardless of the recording, a tube amp may suit you.
They should not, and where they do the page says why. This database records what the maker printed and links the document; where a figure had to be derived, the page labels it derived and names the method. Where a maker contradicts itself — the same sensitivity for three different impedance versions, or two figures six decibels apart for near-identical models — the published number stays and the contradiction is flagged next to it. Nothing is quietly corrected. The method is written up here, and the whole database downloads as CSV so you can check it.
On the three numbers a maker can be held to, more often than not. For 265 of the 280 sources here there is a cheaper one that does the same job as a headphone output: it reaches 100 dB on every headphone the dearer one reaches, and matches it wherever the dearer one publishes an output impedance or a noise figure. Only 15 have nothing cheaper that matches them, and the dearest of those is the Topping L30 II at $149 — 215 products here cost more than that. None of this says the expensive box is not better built, better connected or nicer to use. It says the spec sheet stops separating them early. The 15 exceptions are listed here.
Almost never, and not because the makers are lying. A range without a tolerance is unfalsifiable: “5 Hz – 50 kHz” does not say the headphone plays 5 Hz at a useful level, only that something was picked up there. The figure that turns it into a claim is the ±dB beside it. Of the 578 models checked against their maker's own document, 490 print a range and 58 of those — 12 per cent — print the tolerance. The audit counts it maker by maker, and publishes no measurement of its own.
For power, usually yes. For output impedance, often not, and that is the half people miss. A headphone output designed around 250Ω studio monitors can sit far above where a multi-driver in-ear wants it: of the 43 interfaces here that publish the figure, the median is 10Ω against 0.18Ω for desktop amplifiers, and 28 of them are at 8Ω or more. There are 65 interfaces in this database and every one of them has its numbers on its own page. The category is set out here.
Because hiss is the source's noise floor played through whatever is efficient enough to reveal it, and in-ears usually are. The same microvolts land at a different loudness in your ear depending on sensitivity and impedance. 115 of the 280 sources here publish a noise figure, their median is 2 µV, and on that much noise the median in-ear in this database sits at about 8 dB SPL of hiss and the median full-size model at about -2 dB SPL — a gap of 10 dB from the same amplifier. Push the noise up to the 25.18 µV of the noisiest source here that publishes one, the Schiit Mjolnir 3, and 204 of the 222 in-ears cross the 20 dB SPL where a quiet room stops hiding it, against 181 of the 345 full-size models. The hiss calculator runs it for your own pair.
It is a real engineering achievement, and I enjoyed owning one. Whether the gap between it and a $500 studio DAC justifies the price difference is a question only your bank account and your ears can answer together. My honest answer, having owned both: no.
Almost certainly more than anything you own needs. Nobody prints volts, but every power rating contains them: take the square root of watts times ohms. Do that for the 240 products here that state a power figure at a named load and the middle of the range lands on 3.3 V. Nothing in this catalogue of 567 headphones asks for more than 1.73 V at a 100 dB SPL peak — that worst case is the HiFiMAN Susvara, and it is roughly half what the typical amplifier here has. Every one of those figures is listed, together with the warning that goes with them: volts worked out from a rating into 600Ω are not volts you get at 16Ω, where current runs out first.
For loudness, no. The median of the 222 in-ears here needs 0.32 mW for a 100 dB SPL peak, which is inside what a phone jack manages. The two things that do separate sources on in-ears are the other two axes, and both run the opposite way from power: only 85 of the 280 sources here reach 100 dB on every one of the 222 — the low-impedance, low-sensitivity ones are the hard cases — and of the 83 sources that publish a noise figure, only 5 stay under the threshold of hearing in all of them. Buying an in-ear amplifier for power is usually the wrong reason; buying one for a quiet, low-impedance output can be the right one.
Not on in-ears, and the database shows the trade rather than asserting it. 37 sources here deliver a watt or more into 32Ω and publish a noise figure. Of those, 5 stay under the threshold of hearing in all 222 in-ears. The rest are audible between tracks with sensitive in-ears, not because they are badly made but because a design that swings large voltages has a noise floor scaled to those voltages. On a 300Ω headphone that noise floor disappears. The hiss page lists every published figure with where it lands.
Usually yes, and this is the clearest case of the folklore being backwards. The Beyerdynamic DT 880 Edition (600Ω) needs 2.5 mW and 1.23 V for a 100 dB SPL peak — almost no power at all, because at 600Ω the current is tiny. 44 of the 51 USB dongles in this database have the power for it. High impedance costs volts, not watts, and volts are the thing modern dongles have. What a 600Ω headphone will not do is get loud from a source whose voltage is limited by a small battery rail, which is a different sentence from “it needs a desktop amplifier”.
It depends entirely on what you plug in, and the arithmetic is unforgiving at one end. The one-eighth rule wants the source below an eighth of the headphone impedance, so 50Ω is satisfied only above 400Ω — and 6 of the 567 non-electrostatic models here are that high. On 250Ω studio headphones the effect is small and nobody notices. On a multi-driver in-ear whose impedance swings with frequency it becomes a tone control. 12 sources here publish 50Ω or more, mostly audio interfaces, and a series resistor on a headphone output is a deliberate choice that protects the amplifier in a live room. It is not sloppiness; it is a design for a different headphone. Every published figure is listed and ranked here.