The Truthear PURE is 13.8Ω with a sensitivity of 105.4 dB/mW, which is 124.0 dB/V. To reach 100 dB SPL — genuinely loud, louder than most people listen — it needs 0.29 mW, or 63 mV across the drivers.
That puts it in the easy category. A phone, a laptop headphone jack or the cheapest USB dongle will drive it to painful levels. Of the 280 sources in the database, 280 have at least 10 dB of headroom and another 0 have enough. The cheapest portable source that does the job is the Apple USB-C dongle (US) at $9.
Sensitivity here is in dB per milliwatt. Why the unit matters.
Truthear publishes this as 124 dB/Vrms (@1kHz) — a figure per volt, not per milliwatt. At 13.8Ω the two differ by 18.6 dB, so the 105.4 dB/mW above is that published number converted, not a different measurement.
This is the conversion that online calculators skip. Quote the per-volt number as if it were per-milliwatt and this headphone looks 19 dB easier to drive than it is — which is roughly the difference between a dongle being enough and not being enough.
Truthear prints the impedance as 13.8Ω±15% @1kHz, not as a bare number. Everything on this page is calculated with the nominal 13.8Ω, and the rest of that line is quoted here rather than tidied away, because how a figure is qualified is part of the specification too.
Source: truthear.com. How this data was built.
| As it is labelled | As printed | Tolerance | Standard |
|---|---|---|---|
| Frequency Response Range | 7-40kHz (IEC61094, Free Field) | not printed | IEC61094 (free field) |
| Effective Frequency Response Range | 20-20kHz (IEC60318-4, -3dB) | -3 dB | IEC60318-4 |
Truthear prints two frequency ranges for the Truthear PURE. The wide one carries no conditions at all; the narrow one names a measurement standard and a tolerance. Only the second is a specification — the first is a headline.
This is one of only 58 models — out of the 490 whose maker prints a range at all — that also print the tolerance. That is what makes it a specification rather than a headline.
Only what the maker printed; maker by maker.
| Level | What it is | Power | Voltage | Current |
|---|---|---|---|---|
| 85 dB SPL | quiet background listening | 0.01 mW | 11 mV | 0.8 mA |
| 95 dB SPL | normal listening | 0.09 mW | 35 mV | 2.6 mA |
| 100 dB SPL | loud listening | 0.29 mW | 63 mV | 4.6 mA |
| 105 dB SPL | very loud | 0.91 mW | 0.11 V | 8.1 mA |
| 110 dB SPL | peaks on dynamic music | 2.9 mW | 0.20 V | 14.5 mA |
Most people listen between 75 and 85 dB; the 100 dB row leaves room for peaks.
The 15 cheapest of the 280 sources here that reach 100 dB SPL into 13.8Ω with at least 10 dB of headroom and no known hiss or output-impedance problem with these headphones. All 280 sources, judged for these headphones.
| Source | Type | Price | Power into 13.8Ω | Headroom | Verdict |
|---|---|---|---|---|---|
| FiiO SnowSky Tiny A | USB dongle | $22 | 39 mW | +21 dB | Comfortable |
| FiiO SnowSky Tiny B | USB dongle | $22 | 59 mW | +23 dB | Comfortable |
| Tanchjim Stargate II | USB dongle | $40 | 71 mW | +24 dB | Comfortable |
| ddHiFi TC35AL | USB dongle | $46 | 91 mW | +25 dB | Comfortable |
| ddHiFi TC35Air | USB dongle | $46 | 91 mW | +25 dB | Comfortable |
| Fosi Audio N3 | Bluetooth receiver | $50 | 60 mW | +23 dB | Comfortable |
| Hidizs SD2 | USB dongle | $50 | 30 mW | +20 dB | Comfortable |
| iFi GO link | USB dongle | $59 | 30 mW | +20 dB | Comfortable |
| Kiwi Ears Allegro Pro | USB dongle | $60 | 29 mW | +20 dB | Comfortable |
| ddHiFi TC35Pro (Mountain2) | USB dongle | $66 | 28 mW | +20 dB | Comfortable |
| DUNU DTC 480 | USB dongle | $70 | 28 mW | +20 dB | Comfortable |
| EPZ TP35 Pro | USB dongle | $70 | 48 mW | +22 dB | Comfortable |
| Aiyima A2 Pro | desktop DAC/amp | $75 | 65 mW | +24 dB | Comfortable |
| ddHiFi TC35Pro (Eye2) | USB dongle | $76 | 28 mW | +20 dB | Comfortable |
| ddHiFi TC44 Pro E2 | USB dongle | $99 | 108 mW | +26 dB | Comfortable |
Hiss. At 124.0 dB/V these are sensitive enough to reveal a source's own noise floor. The noisiest source in the database, the Schiit Mjolnir 3, would put its hiss at roughly 32 dB SPL in these headphones — clearly audible in quiet passages. Check your own source.
Output impedance. At 13.8Ω these want a source output impedance below 1.73Ω to satisfy the one-eighth rule; 40 of the 192 sources that publish one miss it. Check yours here.
15Ω · 104.8 dB/mW · Easy
See requirements →17.5Ω · 99.9 dB/mW · Easy
See requirements →10Ω · 97.5 dB/mW · Easy
See requirements →25Ω · 108.0 dB/mW · Easy
See requirements →16Ω · 106.0 dB/mW · Easy
See requirements →16Ω · 106.0 dB · Easy
See requirements →Compared with its stablemates: vs Hexa · vs Hola · vs Nova · vs Zero · vs Zero:2 · vs ZERO:BLUE2 · vs Zero:RED.