Short answer
Both are desktop amplifiers, $375 against $350.
The Lake People G103-S Mk II reaches 100 dB on 566 of the 567 models here, the Bottlehead Crack (OTL kit) on 565.
| Specification | Bottlehead Crack (OTL kit) | Lake People G103-S Mk II |
|---|---|---|
| Power into 32Ω | 271 mW | 1.0 W |
| Power into 150Ω | 403 mW | 804 mW |
| Power into 300Ω | 333 mW | 580 mW |
| Power into 600Ω | 227 mW | 340 mW |
| Output impedance | 120.0 Ω | 0.1 Ω |
| Output noise | not published | 6.15 µV |
| Price | $375 | $350 |
| Headphones it reaches 100 dB on out of 567 | 565 | 566 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Load | Bottlehead Crack (OTL kit) | Lake People G103-S Mk II |
|---|---|---|
| 32 Ω | Derived | Published |
| 150 Ω | Derived | Derived |
| 300 Ω | Published | Published |
| 600 Ω | Derived | Published |
Both makers publish a power rating. Bottlehead Crack (OTL kit) publishes at 300 Ω; Lake People G103-S Mk II at 32 Ω, at 300 Ω and at 600 Ω. The other rows are worked out from those.
So the two columns are not equally firm row by row: at 32 Ω and at 600 Ω only the Lake People G103-S Mk II figure is the maker’s own. On those rows the derived number is the one to doubt first.
1 headphone reaches 100 dB on the Lake People G103-S Mk II but not on the Bottlehead Crack (OTL kit) — Moondrop PARA.
567 headphones are left alone by the Lake People G103-S Mk II under the one-eighth rule but coloured by the Bottlehead Crack (OTL kit) (64 Audio Aspire 1, 64 Audio Fourte, 64 Audio Nio, 564 more).
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 HiFiMAN Susvara: Lake People G103-S Mk II has +14 dB of headroom there against +7 dB. 6 dB is about 4.3 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) because that maker publishes no output noise figure.
| Headphone | Impedance | Needs | Bottlehead Crack (OTL kit) headroom | Lake People G103-S Mk II headroom | Bottlehead Crack (OTL kit) hiss | Lake People G103-S Mk II hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +33 dB damping | +38 dB | not published | 30 dB |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +13 dB damping | +18 dB | not published | 10 dB |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +26 dB damping | +32 dB | not published | 8 dB |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +27 dB damping | +30 dB | not published | 4 dB |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +14 dB damping | +20 dB | not published | 3 dB |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +22 dB damping | +24 dB | not published | -3 dB |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +17 dB damping | +19 dB | not published | -7 dB |
| HiFiMAN Susvara | 60 Ω | 50 mW | +7 dB damping | +14 dB | not published | -9 dB |
The Bottlehead Crack (OTL kit) costs $25 more than the Lake People G103-S Mk II, 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 Lake People G103-S Mk II does not — not on power, not on the one-eighth rule, not on hiss. The traffic runs the other way: the cheaper Lake People G103-S Mk II drives one model to 100 dB and leaves 567 alone under the one-eighth rule 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 Lake People G103-S Mk II.