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 Impedance
Ensures optimal control and cleaner sound across a wide range of full-size headphones and IEMs.

Efficient Cooling and Thermal Stability
Keeps dust out while maintaining airflow to protect internal components.

Compact, Yet Powerful
Crafted 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-One
It 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