Fosi Audio GR70 | Tube Headphone Amplifier and Preamp

The Fosi Audio GR70 Features a Thoughtfully Selected Vacuum Tube Combination For a Highly Musical and Authentic Analog Sound

Desktop vacuum tube headphone amp and preamp General Electric 5654W and Sovtek 6Ж4 replaceable tubes Features adjustable impedance, bass and treble control Supports 16- 300Ω headphone impedance

Quad-Tube Dual Amplification Built with two replaceable General Electric 5654W and two Sovtek 6Ж4 vacuum tubes, the Fosi GR70 amp offers a customizable auditory experience. Immerse yourself in the authentic warmth and smoothness of analog audio. The 5654W tubes boost voltage, while the 6Ж4 tubes handle power amplification. This setup delivers balanced, transparent, and textured sound. Vintage Charm with Modern Precision The GR70 is a two-in-one headphone amp and preamp. Easily integrate this tube preamp into your home audio system with its multiple headphone jacks and RCA input/output options.

This tube headphone amp preamplifier offers intuitive controls, including a large volume knob, dual-side ventilation holes, bass/treble controls, and high + low impedance mode switching. Additional Features Switchable Output ImpedanceEnsures optimal control and cleaner sound across a wide range of full-size headphones and IEMs. Efficient Cooling and Thermal StabilityKeeps dust out while maintaining airflow to protect internal components. Compact, Yet PowerfulCrafted with a CNC-machined aluminum alloy body, the GR70 is both durable and refined. Despite its compact size, it delivers up to 300mW power output and 1.2V RCA output with SNR ≥97dB—offering warm, clean, and dynamic sound. Two-in-OneIt supports low and high impedance modes switching to adapt 16Ω-300Ω headphones, and features 6.35mm/3.5mm headphone jacks on the front and RCA Input/Output on the rear for home audio HiFi system integration.

Specifications

Input: RCA Output: RCA, 6.35mm headphones, 3.5mm headphones

Rated Power Output

Low Gain: 67mW/32Ω High Gain: 830mW/32Ω

Headphone Impedance

Low Impedance Mode: 16Ω-120Ω High Impedance Mode: 120Ω-300Ω

Frequency Response: 20Hz-20kHz (±1dB) SNR: ≥93dB Dynamic Range: 94dB

THD

RCA OUT: ≤0.26% PHONE: ≤0.5%

Noise Floor

RCA OUT: ≤20uV PHONE: 56uV

Cross Talk

RCA OUT: -63dB PHONE: -65dB

Power Input: DC 12V/3A

In the Box

Fosi Audio GR70 Tube Amp (2x) 6Ж4 Vacuum Tube (2x) 5654W Vacuum Tube 12V/3A power supply (2x) Tube cover User manual