Both are audio interfaces, $299 against $299. This page puts them side by side on the only three things a maker can be held to — power, output impedance and noise — and then asks the question that actually matters: which headphones do they treat differently?
On raw power they are level: each reaches 100 dB on 565 of the 567 non-electrostatic models here.
| Specification | Apogee BOOM | SSL 2 Plus MkII |
|---|---|---|
| Power into 32Ω | 240 mW | 374 mW |
| Power into 150Ω | 51 mW | 80 mW |
| Power into 300Ω | 26 mW | 40 mW |
| Power into 600Ω | 13 mW | 20 mW |
| Output impedance | 0.5 Ω | 1 Ω |
| Output noise | not published | not published |
| Price | $299 | $299 |
| Headphones it reaches 100 dB on out of 567 | 565 | 565 |
A figure marked not published is missing from the maker’s own material, which is not the same as being good or bad. Where one of these two publishes a number and the other does not, the comparison on that axis cannot be made at all — and saying so is more useful than guessing.
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.
14 headphones are left alone by the Apogee BOOM under the one-eighth rule but coloured by the SSL 2 Plus MkII (64 Audio Nio, 64 Audio Volur, Campfire Audio Andromeda 2023, 11 more).
565 of the 567 models here reach 100 dB on both. That is a power count and nothing more; whether either source suits a given headphone also depends on the two lines above.
Each has a page of its own with every power figure traced to what the maker published and a full headphone list: Apogee BOOM and SSL 2 Plus MkII. Or put either against your own headphones in the source comparison tool.