Short answer
Both are desktop amplifiers, $929 against $1099.
The Gustard H20 reaches 100 dB on 567 of the 567 models here, the Woo Audio WA6 on 566.
| Specification | Gustard H20 | Woo Audio WA6 |
|---|---|---|
| Power into 32Ω | 12.0 W | 580 mW |
| Power into 150Ω | 2.7 W | 536 mW |
| Power into 300Ω | 1.3 W | 460 mW |
| Power into 600Ω | 670 mW | 400 mW |
| Output impedance | not published | not published |
| Output noise | not published | not published |
| Price | $929 | $1099 |
| Headphones it reaches 100 dB on out of 567 | 567 | 566 |
Not published means the maker leaves it out, so that axis cannot be compared.
| Load | Gustard H20 | Woo Audio WA6 |
|---|---|---|
| 32 Ω | Published | Published |
| 150 Ω | Published | Derived |
| 300 Ω | Published | Published |
| 600 Ω | Published | Published |
Both makers publish a power rating. Gustard H20 publishes at 32 Ω, at 150 Ω, at 300 Ω and at 600 Ω; Woo Audio WA6 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 150 Ω only the Gustard H20 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 Gustard H20 but not on the Woo Audio WA6 — Symphonium Titan.
566 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 HE400se: Gustard H20 has +31 dB of headroom there against +18 dB. 13 dB is about 21 times the power, which matters for peaks rather than for how loud the music sits.
The hiss columns are empty for Gustard H20 and Woo Audio WA6 because neither maker publishes no output noise figure.
| Headphone | Impedance | Needs | Gustard H20 headroom | Woo Audio WA6 headroom | Gustard H20 hiss | Woo Audio WA6 hiss |
|---|---|---|---|---|---|---|
| Shure SE846 | 9 Ω | 0.04 mW | +49 dB | +36 dB | not published | not published |
| Campfire Audio Andromeda 2020 | 9 Ω | 4.0 mW | +29 dB | +16 dB | not published | not published |
| Audeze LCD-2 Classic | 70 Ω | 0.79 mW | +38 dB | +28 dB | not published | not published |
| Beyerdynamic DT 1990 Pro (250Ω) | 250 Ω | 0.63 mW | +34 dB | +29 dB | not published | not published |
| HiFiMAN HE400se | 25 Ω | 7.9 mW | +31 dB | +18 dB | not published | not published |
| Audio-Technica ATH-R70X | 470 Ω | 1.6 mW | +27 dB | +24 dB | not published | not published |
| Sennheiser HD 600 | 300 Ω | 6.6 mW | +23 dB | +18 dB | not published | not published |
| HiFiMAN Susvara | 60 Ω | 50 mW | +21 dB | +10 dB | not published | not published |
The Woo Audio WA6 costs $170 more than the Gustard H20, and on these three axes the money buys nothing: among the 567 models here there is not one that the Woo Audio WA6 handles and the Gustard H20 does not — not on power, not on the one-eighth rule, not on hiss. The traffic runs the other way: the cheaper Gustard H20 drives one model to 100 dB that the Woo Audio WA6 does not.
Only published figures count here; blank axes are counted separately.
Each in full: Gustard H20 and Woo Audio WA6.