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Fosi Audio Fosi Audio GR70 Tube Headphone Amp
- Pure Tube Amplification
- Adjustable Impedance and bass & treble Control
- 2-in-1 Headphone Amp and Preamp
- Supports 16–300Ω Headphone Impedance
GR70 Vacuum Tube Headphone Amp
Featuring two replaceable 5654W and two 6Ж4/6Ж8 vacuum tubes, it offers a customizable auditory experience. Immerse yourself in the authentic warmth and smoothness of analog audio.
Integrating 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.
- Input: RCA; Output: RCA, 6.35mm/3.5mm Headphone Output;
- Rated Power Output: 90mW@32Ω; Max Power Output: 300mW@32Ω; Power Input: DC 12V/3A;
- Headphone Impedance: Low Mode: 16Ω-120Ω, High Mode: 120Ω-300Ω;
Quad-Tube Dual-Stage Amplification
Thoughtfully selected tube combination for a musical and immersive sound.
Ideal for Headphone Enthusiasts
It pairs excellently with over-ear and in-ear headphones for superior audio.
Ideal Partner to V3 & Q6
It pairs perfectly with power amps and passive speakers for a top-notch audio setup.
Customize Your Unique Sound
With central detents to easily restore the natural sound.
Large Top-Mounted Volume Knob
Built-in precision damped potentiometer for smooth, accurate control.
Switchable Output Impedance
Ensuring optimal control and cleaner sound across a wide range of full-size cans and IEMs.
Efficient Cooling and Thermal Stability
Keeps dust out while maintaining airflow to protect internal components.
A Blend of Metal and Elegance
Full aluminum alloy body, finely sandblasted, featuring a minimalist and durable design.
- Pure Tube-Amplification: The GR70 headphone tube amp combines vintage charm with modern tech, delivering authentic tube essence. Perfect for headphone enthusiasts, it pairs excellently with over-ear and in-ear headphones for superior audio
- Quad Tubes: Features two 5654W and two 6Ж4/6Ж8 vacuum tubes for two-stage amplification. The 5654W tubes boost voltage, while the 6Ж4/6Ж8 tubes handle power amplification. This setup delivers balanced, transparent, and textured sound
- User-Friendly Design: This tube headphone amp preamplifier offers intuitive controls, including a large volume knob, dual-side ventilation holes, bass & treble controls, high and low impedance mode switching, making it versatile enough
- 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
- 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
- GR70 Main Unit *1
- 6Ж4/6Ж8 Vacuum Tubes *2
- 5654 Vacuum Tubes *2
- Tube Protection Covers *2
- 12V/3A Power Supply *1
- User Manual
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Professional Reviews 81/100
Nicely Roasted
Sound Quality
81/100
Build Quality
75/100
Features Usability
81/100
Value for Money
85/100
The GR70 delivers a warm, thick tube character with inviting mid-bass bloom and impressively three-dimensional imaging for the money. Reviews By WaveTheory found its low-impedance friendliness unusually useful in a pure tube design, making it a distinctive match for efficient headphones and listeners chasing a lush, spacious presentation.
What Reviewers Are Saying
Pros
Warm, weighty tube voicing with mid-bass bloom and a fuller, wetter presentation.
Good resolution, separation and three-dimensional imaging with suitably efficient low-impedance headphones.
Unusually accommodating of low-impedance loads for an affordable pure tube headphone amplifier.
&
Cons
Limited power and composure with demanding headphones; high-impedance models can sound grainy, shouty and fatiguing when pushed.
Not an expansive soundstager, despite its strong imaging within the available stage.
Single-ended only, with no balanced headphone connection.
SOUND QUALITY PERFORMANCE 81/100
With headphones it can comfortably drive, the GR70 delivers an appealingly warm, thick and spatially convincing tube presentation. Its limited power, softened treble balance and loss of composure with more demanding headphones keep it from being a universal performer.
Transparency Resolution
86/100
The review finds good resolution, separation and three-dimensional imaging for a roughly $200 amplifier. It is not described as an especially expansive soundstager, but its spatial presentation is said to be convincing within its stage.
Tonal Balance Musicality
84/100
The GR70 has a recognizably tube-like character: warmer than neutral, thicker and somewhat wetter in presentation. Extra upper-bass and lower-midrange energy, together with a rolled-off treble, add bloom and warmth but reduce tonal neutrality.
Dynamics
80/100
The reviewer is clear that this is not a particularly powerful amplifier, although it sounds good at normal levels with suitable headphones. When pushed with demanding headphones at normal listening volume, the midrange can become peaky, shouty and fatiguing.
Noise Floor
75/100
The review provides no direct comments on hiss, hum or background silence. Sensitive-IEM performance and low-level noise behavior are therefore unclear.
Headphone Compatibility
82/100
Its ability to drive lower-impedance loads is described as unusual for a full tube amplifier at this price, and the reviewer enjoyed the HIFIMAN Ananda Unveiled at normal levels. However, limited overall power means it is best matched with headphones it can drive comfortably rather than difficult loads played loudly.
Assessments of Build Quality, Usability, and Overall Propositions.
Build Quality
75/100
The supplied NOS military-spec 5654 tubes are a welcome detail. Beyond that, the review says little about chassis construction, controls, connectors or long-term durability.
Features Usability
81/100
The GR70 is a straightforward single-ended tube amplifier, without balanced connections. Bass and treble controls offer useful flexibility, including a clearly audible mid-bass lift in the high setting, though the reviewer mainly preferred leaving both controls flat.
Value for Money
85/100
At an MSRP around $200 and street pricing near $190, the reviewer considers the GR70 a pretty good, solid option for the listener seeking this particular tube sound. The review does not directly compare its value against competing amplifiers at the price.
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Authorized dealers for Fosi Audio Fosi Audio GR70 Tube Headphone Amp
- Acoustic Technologies — online and in-store — Montréal, Québec, Canada (website)
- Altitudo Audio — online and in-store — Winnipeg, Manitoba, Canada (website)
- Apos Audio — online and in-store — Oakland, California, United States (website)
- Audeos — online and in-store — Żywiec, Województwo śląskie (website)
- Audio 46 — online and in-store — New York, New York, United States (website)
- Audio Domain — online and in-store — Stadtbezirke I, Nordrhein-Westfalen, Germany (website)
- Audio Magic - EU — online and in-store — Wola, Województwo mazowieckie, Poland (website)
- AUDIOPHONICS — in-store — Bordeaux, Nouvelle-Aquitaine, France (website)
- AV Cables — online and in-store — Hornsyld, Denmark (website)
- B&H Photo — online and in-store — New York, New York, United States (website)
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