Short answer
Both are desktop amplifiers, $375 against $370.
The Geshelli Archel 3S Pro reaches 100 dB on 567 of the 567 models here, the Bottlehead Crack (OTL kit) on 565.
| Specification | Bottlehead Crack (OTL kit) | Geshelli Archel 3S Pro |
|---|---|---|
| Power into 32Ω | 271 mW | 1.0 W |
| Power into 150Ω | 403 mW | 213 mW |
| Power into 300Ω | 333 mW | 107 mW |
| Power into 600Ω | 227 mW | 53 mW |
| Output impedance | 120.0 Ω | not published |
| Output noise | not published | not published |
| Price | $375 | $370 |
| Headphones it reaches 100 dB on out of 567 | 565 | 567 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Load | Bottlehead Crack (OTL kit) | Geshelli Archel 3S Pro |
|---|---|---|
| 32 Ω | Derived | Derived |
| 150 Ω | Derived | Derived |
| 300 Ω | Published | Derived |
| 600 Ω | Derived | Derived |
Only one of these two columns starts from a power rating. Bottlehead Crack (OTL kit) publishes one at 300 Ω; Geshelli Archel 3S Pro publishes none at any of these four loads, so its column is worked out from power it published at other loads. Both are arithmetic on a maker’s own figures rather than guesses, and the method used for the Geshelli Archel 3S Pro understates rather than flatters — but at 300 Ω is the only load here at which its maker can be held to a figure.
2 headphones reach 100 dB on the Geshelli Archel 3S Pro but not on the Bottlehead Crack (OTL kit) — Moondrop PARA, Symphonium Titan.
565 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 Campfire Audio Andromeda 2020: Geshelli Archel 3S Pro has +25 dB of headroom there against +13 dB. 12 dB is about 15 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Bottlehead Crack (OTL kit) and Geshelli Archel 3S Pro because neither maker publishes no output noise figure.
| Headphone | Impedance | Needs | Bottlehead Crack (OTL kit) headroom | Geshelli Archel 3S Pro headroom | Bottlehead Crack (OTL kit) hiss | Geshelli Archel 3S Pro hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +33 dB damping | +45 dB | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +13 dB damping | +25 dB | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +26 dB damping | +28 dB | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +27 dB damping | +23 dB | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +14 dB damping | +22 dB | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +22 dB damping | +16 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +17 dB damping | +12 dB | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | +7 dB damping | +10 dB | not published | not published |
The Bottlehead Crack (OTL kit) costs $5 more than the Geshelli Archel 3S Pro, and on these three axes the money buys nothing: among the 567 models here there is not one that the Bottlehead Crack (OTL kit) handles and the Geshelli Archel 3S Pro does not — not on power, not on the one-eighth rule, not on hiss. The traffic runs the other way: the cheaper Geshelli Archel 3S Pro drives 2 models to 100 dB that the Bottlehead Crack (OTL kit) does not.
Only published figures count here; blank axes are counted separately.
Each in full: Bottlehead Crack (OTL kit) and Geshelli Archel 3S Pro.