Fosi GR70 Tube Headphone Amplifier & Preamplifier
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The Fosi Audio GR70 Tube Headphone Amplifier combines classic tube character with modern clarity. Using a dual-stage design with four precision-matched tubes, it delivers natural, transparent sound rich in warmth and texture. Compact, powerful, and beautifully built, the GR70 with tone controls drives a wide range of headphones effortlessly — adding a touch of analogue soul to any digital setup. For greater flexibility and a complete high-fidelity experience, pair it with the Fosi Audio ZD3 DAC for a refined and versatile headphone solution.
The Fosi Audio GR70 Tube Headphone Amplifier blends classic tube warmth with modern engineering in a compact, elegant form. Designed for headphone enthusiasts and home-audio listeners alike, it captures the character of vintage amplification while providing clean, controlled power for today’s high-resolution sources.
At the heart of the GR70 are four vacuum tubes — two 5654W for voltage gain and two 6AC7 tubes for power amplification — forming a two-stage pure-tube topology. This design delivers a smooth, balanced presentation with rich midrange texture, silky treble, and an inviting sense of space. Every note flows naturally, revealing the subtle detail and musicality that make tube listening so distinctive.
Despite its compact footprint, the Fosi GR70 tube headphone amp is a capable performer. It outputs up to 300 mW @ 32 Ω with signal-to-noise ratio ≥ 97 dB, supporting headphones from 16 Ω to 300 Ω across low- and high-impedance modes. Whether driving sensitive IEMs or demanding over-ears, it maintains low distortion and consistent tonal balance.
Built from CNC-machined aluminium, the chassis feels reassuringly solid yet refined. Dual-side ventilation keeps the tubes running cool, while tactile controls — volume, bass, treble, and impedance selection — make the amplifier intuitive to operate. Both 6.35 mm and 3.5 mm headphone outputs, plus RCA input/output, allow integration into desktop or home-hi-fi systems.
For headphones listeners, the Fosi GR70 tube amplifier offers a perfect meeting of nostalgia and precision. Its glow invites you in; its sound keeps you listening — open, warm, and effortlessly musical.
Features
- Four-tube design using two 5654W and two 6AC7 tubes for pure dual-stage amplification
- Supports both low (16 Ω – 120 Ω) and high (120 Ω – 300 Ω) impedance headphones
- Delivers up to 300 mW output @ 32 Ω with SNR ≥ 97 dB and THD ≤ 0.5 %
- Bass and treble controls allow fine-tuning of tonal balance to suit your music
- RCA input and output for integration with home hi-fi or powered speakers
- Front panel offers both 6.35 mm and 3.5 mm headphone outputs
- Durable CNC-machined aluminium enclosure with dual ventilation for thermal stability
- Compact 12 V design suitable for desktop or living-room audio systems
- Hand-finished controls for a refined user experience and classic tube aesthetic
Specifications
| Product Type: | Headphone Amplifier / Pre-Amp |
| Technology: | Tube |
| Inputs: | Stereo RCA |
| Outputs: | Stereo RCA 6.35mm / 3.5mm Headphone out |
| Max Power Output: | 300mW @ 32 Ohm |
| Headphone Impedance: | Low Mode: 16 - 120 Ohm High Mode: 120 - 300 Ohm |
| Frequency Response: | 20 Hz – 20 kHz (± 0.1 dB) |
| THD: |
Headphone output: ≤0.5% RCA output: ≤0.26% |
| SNR: | ≥ 97 dB |
| Dynamic Range: | ≥ 97 dB |
| Tubes: | 2 x 5654W 2 x 6AC7 |
| Outputs: | Speaker binding posts Subwoofer output |
| Power Supply: | 12v DC / 3 A |
| Dimension (WxHxD): | 129 × 46 x 192 mm |
| Weight: | 0.9 kg |
| Finish: | Black anodised aluminium |
Includes
- 1 x GR70
- 2 x 6Ж4/6Ж8 Vacuum Tubes
- 2 x 5654 Vacuum Tubes
- 2 x Tube Protection Covers
- 1 x 12V/3A Power Supply
- 1 x User Manual
Support
About
Fosi Audio, established in Shenzhen in 2017 by Ryan Huang, has emerged as a pioneering force in democratizing high-fidelity sound. Guided by four core tenets—Foresight, Openness, Sincerity, and Innovation—the brand has cultivated a distinguished presence across 150+ nations. Renowned for exceptional sonic value and community-driven engineering, Fosi integrates premium components from industry leaders like Texas Instruments. Their philosophy transcends conventional audio retail, offering both refined finished products and bespoke DIY solutions for the discerning enthusiast seeking uncompromised quality without premium pricing.