On power: 38 of the 39 portable players here reach 100 dB SPL on the AKG K612 Pro. It needs 6.6 mW at its 120Ω, and 1 of them do not get there.
Power is one of three questions and the one that goes wrong least often. The other two — whether the source’s output impedance leaves the frequency response alone, and whether you will hear its noise floor — are answered further down, separately, because a source can pass one and fail another.
The 1 that fall short are Sony NW-A306. The closest of them, the Sony NW-A306, delivers 4.6 mW into 120Ω against the 6.6 mW needed — 1.5 dB short.
The cheapest one that does reach it is the Hidizs AP80 Pro Max at $179, which delivers 19 mW into 120Ω — 5 dB of headroom over the 6.6 mW this headphone needs for 100 dB SPL.
100 dB SPL is a peak level, not a listening level. If you listen at 85 dB the same headphone needs 0.21 mW, which is 15 dB less, and the answer above changes for most of the category. The model page has the full ladder.
Under the one-eighth rule the AKG K612 Pro wants a source below 15.00Ω. Of the 26 portable players here that publish an output impedance, 26 are under it and 0 are not.
The other 13 publish nothing at all on this, so they are not on either side of that count. This site leaves them blank rather than assuming a figure.
Hiss depends on the source’s own noise floor and on how sensitive the headphone is. At 91.8 dB/mW and 120Ω, the AKG K612 Pro turns one microvolt of source noise into about -19 dB SPL — and the threshold where that stops being noticeable in a quiet room is around 20 dB SPL.
Of the 12 portable players here that publish a noise figure, 12 stay below that threshold with this headphone and 0 cross it.
The remaining 27 publish no noise figure, so they cannot be placed on either side.
| Source | Price | Into 120 Ω | Headroom | Output impedance | Hiss in these |
|---|---|---|---|---|---|
| FiiO JM21 | $199 | 68 mW | 10.2 dB | 1 Ω | -15 dB SPL |
| FiiO M11S | $499 | 55 mW | 9.2 dB | 1.5 Ω | -14 dB SPL |
| FiiO M21 | $599 | 109 mW | 12.2 dB | 1.0 Ω | -13 dB SPL |
11 of the 39 portable players here publish all three figures. 11 of those clear all three for the AKG K612 Pro, and the cheapest is the FiiO JM21 at $199.
It delivers 68 mW into 120 Ω where this headphone needs 6.6 mW for 100 dB — 10.2 dB of headroom — its output impedance of 1 Ω sits under the one-eighth ceiling of 15.00 Ω, and its 1.6 µV of noise leaves the hiss 35 dB under the 20 dB SPL threshold this site uses.
Cheapest that satisfies three published numbers is not the same as best, and the sources left out of this count are left out for want of a published figure, not for failing one. How often that happens is its own page.
| Source | Price | Into 120Ω | Output impedance | Hiss in these | Power verdict |
|---|---|---|---|---|---|
| TempoTec Variations V3 Blaze | $179 | 220 mW | not published | not published | Comfortable |
| FiiO JM21 | $199 | 68 mW | 1 Ω | -15 dB SPL | Comfortable |
| TempoTec Variations V6 | $369 | 88 mW | not published | not published | Comfortable |
| iBasso DX180 | $480 | 70 mW | 0.6 Ω | not published | Comfortable |
| FiiO M21 | $599 | 109 mW | 1 Ω | -13 dB SPL | Comfortable |
| Cayin N3 Ultra | $649 | 67 mW | 0.5 Ω | not published | Comfortable |
| FiiO M33 R2R | $730 | 133 mW | 0.8 Ω | -4 dB SPL | Comfortable |
| HiBy R6 Pro II | $750 | 308 mW | not published | not published | Comfortable |
| FiiO M15S | $799 | 178 mW | 1.4 Ω | -9 dB SPL | Comfortable |
| Astell&Kern SR35 | $800 | 80 mW | 1.1 Ω | not published | Comfortable |
| iBasso DX260 | $949 | 70 mW | 0.6 Ω | not published | Comfortable |
| iBasso DX260 MK2 | $949 | 70 mW | 0.6 Ω | -19 dB SPL | Comfortable |
Sorted by how many of the three questions the source answers well, then by price. A blank in a column is a blank in the manufacturer’s own documentation, not a zero.
The AKG K612 Pro on other categories: USB dongles · desktop amplifiers · audio interfaces.
The AKG K612 Pro page has every source in the database against this headphone, and the matcher takes your own numbers.