In this review I’m looking at the ZAHL H1 — basically the “baby brother” to the HM1 I covered a couple of years back — and the headline is simple: this is a palm-sized, summit-level headphone amplifier with the same core sonic DNA as the HM1. The H1 drops some of the pro-oriented extras (like the HM1’s separate linear PSU/umbilical and additional functionality) and instead gives you an integrated, dual-mono class A design with proper ergonomics, three headphone outputs (4-pin XLR, 6.3mm, and 4.4mm), and that familiar stage control that can widen, narrow, or even go full mono. Sound-wise, I’m not going to sugar-coat it: in Class A Servo it’s neutral and reference-first. It doesn’t sweeten, thicken, or “fix” recordings — it tells you what’s actually on the track, for better or worse. The standout trait (and it’s still rare) is the grip and control on demanding planars; that driver reaction is breathtaking on electronic music, and it handles heavy hitters like Susvara OG/Unveiled and other tough loads with ease. The caveats are real though: there’s a slightly “below spicy” presence around the 6–8k region on some material, texture can feel a touch less emphasized versus more euphonic amps, and the price is a tough pill at roughly 8k with tax — even if the performance is absolutely top-tier.