Short answer
Both are desktop DAC/amps, $449 against $549.
On raw power they are level: each reaches 100 dB on 567 of the 567 non-electrostatic models here.
| Specification | JDS Labs Element III MK2 | JDS Labs Element IV |
|---|---|---|
| Power into 32Ω | 2.3 W | 3.2 W |
| Power into 150Ω | 584 mW | 692 mW |
| Power into 300Ω | 292 mW | 347 mW |
| Power into 600Ω | 146 mW | 174 mW |
| Output impedance | 0.7 Ω | 1 Ω |
| Output noise | 2.51 µV | 2 µV |
| Price | $449 | $549 |
| Headphones it reaches 100 dB on out of 567 | 567 | 567 |
| Load | JDS Labs Element III MK2 | JDS Labs Element IV |
|---|---|---|
| 32 Ω | Published | Published |
| 150 Ω | Published | Published |
| 300 Ω | Derived | Derived |
| 600 Ω | Published | Published |
Both makers publish a power rating. JDS Labs Element III MK2 publishes at 32 Ω, at 150 Ω and at 600 Ω; JDS Labs Element IV at 32 Ω, at 150 Ω and at 600 Ω. The other rows are worked out from those.
The two publish at the same loads, which is the one case where the rows of this table can be read straight across.
On power they are interchangeable across this whole database: there is no headphone here that one reaches 100 dB on and the other does not.
11 headphones are left alone by the JDS Labs Element III MK2 under the one-eighth rule but coloured by the JDS Labs Element IV (64 Audio Nio, 64 Audio Volur, Campfire Audio Andromeda 2023, 8 more).
4 headphones stay below the audible-hiss threshold on the JDS Labs Element IV but cross it on the JDS Labs Element III MK2 (Campfire Audio Andromeda 10, Campfire Audio Andromeda 2023, Shure AONIC 5, 1 more).
567 of the 567 models here reach 100 dB on both.
Headroom is at a 100 dB SPL peak.
The widest gap on the list is the Shure SE846: JDS Labs Element IV has +44 dB of headroom there against +42 dB. 1 dB is about 1.4 times the power, which matters for peaks rather than for how loud the music sits.
Hiss below about 20 dB SPL is inaudible in a quiet room.
| Headphone | Impedance | Needs | JDS Labs Element III MK2 headroom | JDS Labs Element IV headroom | JDS Labs Element III MK2 hiss | JDS Labs Element IV hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +42 dB | +44 dB | 22 dB | 20 dB |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +22 dB | +24 dB | 2 dB | 0 dB |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +31 dB | +33 dB | 1 dB | -1 dB |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +27 dB | +28 dB | -4 dB | -6 dB |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +24 dB | +25 dB | -5 dB | -7 dB |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +21 dB | +21 dB | -11 dB | -13 dB |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +16 dB | +17 dB | -15 dB | -17 dB |
| HiFiMAN Susvara | 60 Ω | 50 mW | +14 dB | +15 dB | -17 dB | -19 dB |
The JDS Labs Element IV costs $100 more than the JDS Labs Element III MK2. Out of the 567 models here, that difference buys 4 more models kept below the audible-hiss threshold.
It does not run one way only: the cheaper JDS Labs Element III MK2 leaves 11 models alone under the one-eighth rule that the JDS Labs Element IV does not, which is the part worth checking against your own headphones before paying the difference.
Only published figures count here; blank axes are counted separately.
Each in full: JDS Labs Element III MK2 and JDS Labs Element IV.