Fosi Audio GR70 Tube Headphone Amp Preamp

Fosi Audio GR70 Tube Headphone Amp Preamp with Low & High Impedance Mode

The Fosi Audio GR70 is a headphone tube amp and preamp that manages to bottle up the classic warmth of tubes while keeping everything accessible and modern. At its core, it’s a pure tube-amplification design which delivers that unmistakable analogue richness that headphone enthusiasts crave. Whether you’re pairing it with over-ears or in-ears, the GR70 shines with a natural, textured, and dynamic sound that feels authentic to the tube experience. Add in the glacier-coloured ambient light glowing softly around the chassis, and you’ve got a device that blends vintage charm with a touch of contemporary elegance.

Under the hood, the GR70 packs a serious tube configuration. It comes with two General Electric 5654W tubes handling voltage amplification and two Sovtek 6AC7 tubes for power amplification, creating a balanced and transparent two-stage system. This arrangement doesn’t just look great through the vented sides - it gives your music a layered, engaging presentation with plenty of detail and body. Better still, the tubes are fully replaceable, so you can experiment with different brands and tonalities to personalise your sound. It’s a real treat for anyone who enjoys the hands-on side of Hi-Fi listening.

Ease of use hasn’t been overlooked either. On top there is a large volume control while the straightforward front panel has separate bass and treble controls for tailoring your sound, and both 6.35 mm and 3.5 mm headphone jacks for flexibility. Around the back, you’ll find RCA input and output connections, making it easy to slot into a home Hi-Fi system as a preamp. Dual-side ventilation keeps things running cool, while the high/low impedance switch ensures the amp can adapt to anything from efficient 16Ω headphones up to demanding 300Ω models without breaking a sweat.

Despite its compact footprint, the GR70 delivers impressive performance specs. With up to 300mW of power at 32Ω, a 1.2V RCA output, and a signal-to-noise ratio of at least 97dB, it offers clean, dynamic playback that doesn’t sacrifice detail for warmth. The CNC-machined aluminium alloy body adds durability and refinement, making the unit feel as solid as it sounds. In short, the Fosi Audio GR70 is a thoughtfully designed, great-sounding tube headphone amp and preamp that brings together technical innovation, musicality, and a dash of aesthetic charm - all in a compact and versatile package.

Our Review

The Fosi Audio GR70 is one of those rare pieces of gear that captures the magic of tubes without feeling fussy or old-fashioned, delivering a listening experience that’s both warm and engaging. Its pure tube-amplification design, powered by a two-stage setup of General Electric 5654W and Sovtek 6AC7 tubes, creates a textured, natural sound that feels alive, whether you’re using over-ears or in-ears. Thoughtful touches like dual headphone outputs, separate bass and treble controls, and an impedance switch mean it adapts easily to different setups, while the CNC-machined aluminium chassis with soft glacier lighting gives it a sense of understated elegance. With plenty of power, clean specs, and the option to swap out tubes for your own sonic flavour, the GR70 manages to be both technically impressive and genuinely fun to live with - a compact little amp that feels as good to use as it sounds.