The Zoom AMS-24 is an audio interface at $150. It delivers 30 mW into 32Ω and 5.2 mW into 300Ω, which ranks it 266 of 280 for raw power among the sources in this database.
Measured at 100 dB SPL it has comfortable headroom on 386 of the 567 dynamic and planar headphones catalogued here, enough but not generous on 142, only marginal on 21 and not enough power for 18. Power is published at 32Ω; the rest of the table is derived from those figures. Output noise is not published, so the hiss estimate cannot be run.
The manufacturer publishes 30 mW into 32Ω. Everything else in the table above is worked out from those figures, and this table says which is which.
Derivation holds output voltage steady between and beyond the published loads rather than output power, because that is what an amplifier actually does. The full method is written up here.
Source: zoomcorp.com.
| Load | Power | Status | How it was arrived at |
|---|---|---|---|
| 32 Ω | 30 mW | Published | the manufacturer publishes this figure at this exact load |
| 150 Ω | 9.7 mW | Derived | worked out from the published figure and the published output impedance, through the divider that impedance creates |
| 300 Ω | 5.2 mW | Derived | worked out from the published figure and the published output impedance, through the divider that impedance creates |
| 600 Ω | 2.7 mW | Derived | worked out from the published figure and the published output impedance, through the divider that impedance creates |
Ordered from easiest to hardest to drive. Headroom is measured at 100 dB SPL, which is louder than almost anyone listens — a small negative number means the source still plays loud, just without reserve for peaks.
These figures come from each manufacturer's own sensitivity rating. A handful of planars — the HiFiMAN Susvara and the Abyss AB-1266 in particular — are widely reported to need far more than their published sensitivity implies, so treat a bare pass on those as optimistic rather than settled.
| Headphone | Impedance | Sensitivity | Needs | Headroom | Verdict |
|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 114.0 dB/mW | 0.04 mW | +23 dB | Comfortable damping |
| 64 Audio U12t | 12.6 Ω | 108.0 dB/mW | 0.16 mW | +19 dB | Comfortable damping |
| Shure SE215 | 17 Ω | 107.0 dB/mW | 0.20 mW | +19 dB | Comfortable damping |
| Moondrop Aria | 32 Ω | 107.1 dB/mW | 0.19 mW | +22 dB | Comfortable damping |
| Audeze LCD-X 2021 | 20 Ω | 103.0 dB/mW | 0.50 mW | +16 dB | Comfortable damping |
| Truthear Hexa | 20.5 Ω | 103.1 dB/mW | 0.49 mW | +16 dB | Comfortable damping |
| Sennheiser IE 200 | 18 Ω | 101.6 dB/mW | 0.69 mW | +14 dB | Comfortable damping |
| Sony MDR-7506 | 63 Ω | 106.0 dB/mW | 0.25 mW | +18 dB | Comfortable damping |
| Meze 99 Classics | 32 Ω | 103.0 dB/mW | 0.50 mW | +18 dB | Comfortable damping |
| Focal Clear MG | 55 Ω | 104.0 dB/mW | 0.40 mW | +17 dB | Comfortable damping |
| Philips SHP9500 | 32 Ω | 101.0 dB | 0.79 mW | +16 dB | Comfortable damping |
| Focal Utopia | 80 Ω | 104.0 dB/mW | 0.40 mW | +16 dB | Comfortable |
| Meze Empyrean | 32 Ω | 100.0 dB | 1.0 mW | +15 dB | Comfortable damping |
| Campfire Audio Andromeda 2020 | 9 Ω | 94.0 dB | 4.0 mW | +3 dB | Enough damping |
| Etymotic ER2SE | 15 Ω | 96.0 dB/mW | 2.5 mW | +7 dB | Enough damping |
| AKG K371 | 32 Ω | 99.1 dB/mW | 1.2 mW | +14 dB | Comfortable damping |
| Audio-Technica ATH-M50X | 38 Ω | 99.0 dB/mW | 1.3 mW | +13 dB | Comfortable damping |
| Beyerdynamic DT 900 Pro X | 48 Ω | 100.0 dB/mW | 1.0 mW | +13 dB | Comfortable damping |
| Audeze LCD-2 Classic | 70 Ω | 101.0 dB/mW | 0.79 mW | +13 dB | Comfortable damping |
| Grado SR80x | 38 Ω | 98.0 dB/mW | 1.6 mW | +12 dB | Comfortable damping |
| Sennheiser HD 560S | 120 Ω | 100.8 dB/mW | 0.83 mW | +11 dB | Comfortable |
| HiFiMAN Edition XS | 18 Ω | 92.0 dB | 6.3 mW | +4 dB | Enough damping |
| HiFiMAN Arya Stealth | 32 Ω | 94.0 dB | 4.0 mW | +9 dB | Enough damping |
| Dan Clark Audio AEON 2 Closed | 13 Ω | 90.0 dB/mW | 10 mW | +1 dB | Marginal damping |
| Audeze LCD-5 | 14 Ω | 90.0 dB/mW | 10 mW | +1 dB | Marginal damping |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 102.0 dB/mW | 0.63 mW | +10 dB | Enough |
| HiFiMAN HE400se | 25 Ω | 91.0 dB | 7.9 mW | +5 dB | Enough damping |
| HiFiMAN Sundara | 32 Ω | 92.0 dB | 6.3 mW | +7 dB | Enough damping |
| Dan Clark Audio Stealth | 23 Ω | 90.0 dB/mW | 10 mW | +3 dB | Enough damping |
| Fostex T50RP MK3 | 50 Ω | 92.0 dB/mW | 6.3 mW | +5 dB | Enough damping |
| AKG K702 | 62 Ω | 92.9 dB/mW | 5.1 mW | +5 dB | Enough damping |
| ZMF Verite Closed | 300 Ω | 99.0 dB/mW | 1.3 mW | +6 dB | Enough |
| Sennheiser HD 650 | 300 Ω | 97.8 dB/mW | 1.7 mW | +5 dB | Enough |
| Sennheiser HD 800S | 300 Ω | 96.8 dB/mW | 2.1 mW | +4 dB | Enough |
| Beyerdynamic DT 770 Pro (250Ω) | 250 Ω | 96.0 dB | 2.5 mW | +4 dB | Enough |
| Audio-Technica ATH-R70X | 470 Ω | 98.0 dB/mW | 1.6 mW | +3 dB | Enough |
| ZMF Atrium | 300 Ω | 96.0 dB/mW | 2.5 mW | +3 dB | Enough |
| Abyss AB-1266 Phi TC | 50 Ω | 88.0 dB/mW | 16 mW | +1 dB | Marginal damping |
| Sennheiser HD 600 | 300 Ω | 91.8 dB/mW | 6.6 mW | -1 dB | Not enough |
| HiFiMAN Susvara | 60 Ω | 83.0 dB | 50 mW | -4 dB | Not enough damping |
The manufacturer does not publish an output noise figure for this source, so the hiss estimate that runs on every other page here cannot be run on this one. Rather than substitute a plausible number, this page leaves the question open.
If you know the noise figure from a measurement you trust, the hiss calculator takes it directly and tells you where that noise lands in your own in-ears.
At 10Ω output impedance, the one-eighth rule says this source suits headphones of 80.0Ω and above. 510 of the 567 models here fall below that. That is most of the database, not a niche — 222 of them multi-driver in-ears, and the mismatch tilts the frequency response audibly rather than subtly.
The rule is a rule of thumb, not physics: a source impedance below one eighth of the headphone's keeps the interaction under about 1 dB. The checker works it out for any pair.
| Product | Price |
|---|---|
| Zoom AMS-24 | $150 |
| Zoom AMS-44 | $200 |
On every figure Zoom publishes for this headphone output, the Zoom AMS-24 is identical to the Zoom AMS-44. Each of them states power at 32 Ω and an output impedance of 10 Ω — and each states the same values.
They do not cost the same. The spread across the 2 of them is $50, and none of that difference is visible in the figures above.
Identical published figures do not mean identical products. A spec sheet for a headphone output covers power, output impedance and noise. It says nothing about the converter, the inputs, the case, the battery, the volume control or how any of it sounds, and those are real differences that cost real money. What this section says is narrower and worth saying anyway: if you are choosing between these on what the maker printed about the headphone jack, there is nothing to choose.
15 groups of products in this database share a spec sheet this way, 36 products in all.
| Source | Type | Price | Into 300 Ω | Output impedance | Output noise |
|---|---|---|---|---|---|
| FiiO KA11 | USB dongle | $29 | 22 mW | 0.7 Ω | 1.7 µV |
| FiiO BTR13 | Bluetooth receiver | $59 | 10.0 mW | 0.6 Ω | 1.0 µV |
| iFi GO link | USB dongle | $59 | 14 mW | 0.4 Ω | not published |
Of the 280 sources here, 22 do everything the Zoom AMS-24 does as a headphone output: reach 100 dB on every headphone it reaches and stay inside the one-eighth rule wherever it does. The cheapest of them is the FiiO KA11 at $29, against this one’s $150 — $121 less, and a USB dongle rather than an audio interface.
The cheaper one also publishes a noise figure, which the Zoom AMS-24 does not — so on the paperwork it is ahead, not merely level.
This counts a headphone output and nothing else. Inputs, converters, microphone preamps, balanced outputs, the volume control, the case and the warranty are all outside it, and any of them can be the reason to buy the dearer box. What the count does say is that the three numbers a maker can be held to do not separate them.
$149 · 27 mW into 32Ω · output Ω not published
Compare →$149 · 139 mW into 32Ω · 10 Ω out
Compare →$149 · 84 mW into 32Ω · output Ω not published
Compare →$149 · 139 mW into 32Ω · 10 Ω out
Compare →$139 · 31 mW into 32Ω · 50 Ω out
Compare →$130 · 26 mW into 32Ω · <0.1 Ω out
Compare →Worked out in advance against its closest rivals: vs Arturia MiniFuse 1 · vs Arturia MiniFuse 2 · vs IK Multimedia AXE I/O ONE · vs SSL 2 MkII · vs Zoom AMS-22 · vs Zoom UAC-232. Each of those pages lists the headphones that tell the two apart.
Or put any two side by side in the source comparison tool, or run your own headphones through the amplifier matcher. Or see every Zoom source in the database, and how much of what this site says about them came from Zoom’s own documents.