Fosi Audio GR70 Tube Amplifier with quad-tube setup and RCA input, designed for Hi-Fi headphone and speaker systems.
Fosi Audio GR70 Tube Headphone Amp Preamp on a desktop setup, showcasing analog sound warmth and premium build.
Close-up of Fosi Audio GR70's quad-tube dual-stage amplification, highlighting vintage vacuum tubes for rich audio output.
Fosi Audio GR70 Tube Amplifier features user-friendly controls including volume, bass, treble, and impedance switch.
Fosi Audio GR70 used as headphone amp and tube preamp, enhancing audio systems with analog tube character.
Disassembled view of Fosi Audio GR70 Tube Amplifier showing metal chassis and components for elegant, durable design.
Fosi Audio GR70 rear and front panel overview with RCA input/output, headphone jack, and control knobs labeled.
Connection diagram for Fosi Audio GR70 Tube Amplifier showing compatibility with headphones, speakers, and audio sources.
Box contents of Fosi Audio GR70 including main unit, vacuum tubes, power supply, tube covers, and user manual.

Fosi Audio

Fosi Audio - GR70 Tube Amplifier & Preamplifier

Sale price₹ 18,290Regular price ₹ 28,999

    Warm and Rich Analog Sound with Tube Amplification

    Drives headphones from 16Ω to 300Ω impedance

    Dual gain modes for LO-Z and HI-Z headphones

    Adjustable Impedance, Bass and Treble Control

    Solid CNC Aluminum Built Chassis

    Utilizes 6AC7 and 5654 Vacuum Tubes

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Pickup available at Naraina, New Delhi

You will be notified once the product is available for pickup, as per the pre-order timeline.

Description

The all new GR70 by Fosi Audio lets you experience the classic warmth of tube sound with its premium Quad-Tube setup. The GR70 is equipped with 2× 6AC7 Pentodes and 2× 5654 Driver Tubes which provide a rich and detailed but still natural sound. Built for both headphone enthusiasts and Hi-Fi lovers, the GR70 effortlessly drives headphones with impedance ranging from 16Ω to 300Ω. This amplifier also features switchable gain modes for LO-Z and HI-Z setups. The GR70 combines classic tube tone with modern flexibility by offering RCA inputs/outputs, 3.5mm and 6.35mm headphone jacks. Fosi Audio has also provided its customers with dedicated bass & treble controls for fine-tuning the sound to their preferences. Encased in a solidly built CNC-machined aluminum chassis, this compact amp is as durable as it is stylish, making it the centerpiece of any desktop or audio rig.

QUAD-TUBE SETUP FOR PURE ANALOG WARMTH

The Fosi Audio GR70 features a quad-tube setup with 2× 6AC7 Pentode Tubes serving as power amplifiers and 2× 5654 Driver Tubes for voltage amplification. The 6AC7 pentode is known for its high transconductance and the ability to deliver warm as well as smooth mids which represents classic tube character. The 5654 tubes enhance signal gain with clarity and accuracy leading to a rich, textured, and organic sound that audiophiles appreciate.

ROBUST POWER OUTPUT AND VERSATILE PERFORMANCE

This headphone amplifier provides ample power for a wide range of headphones, supporting impedances from 16Ω up to 300Ω. It supports two-stage amplification with driver tubes handling voltage gain and power tubes for driving output. The amp also offers dual gain modes to optimize performance for low-impedance (LO-Z) and high-impedance (HI-Z) headphones, ensuring efficient power delivery and minimal distortion. This power architecture allows the GR70 to perform well from portable earbuds or IEM’s to demanding Hi-Fi Headphones, preserving detail and delivering a warm yet immersive listening experience.

VERSATILE CONNECTIONS FOR ANY AUDIO SETUP

The GR70 offers versatile connectivity options to integrate effortlessly into any audio setup. A dedicated RCA line input lets you connect CD players, DACs, or streaming devices, while the RCA pre-out enables you to use the GR70 as a warm-sounding tube preamplifier for speakers or power amps. On the front panel, both 3.5mm and 6.35mm headphone jacks cater to a wide range of headphones without needing adapters. With this flexible I/O layout, the GR70 fits seamlessly into everything from minimalist desktop systems to full Hi-Fi environments.

ON-THE-GO CONTROLS FOR CUSTOMIZATION

Fosi Audio has put sound shaping at your fingertips with their latest offering ‘GR70’. A smooth-turning volume knob allows accurate level control, while independent bass and treble knobs give you the ability to add warmth, punch, or sparkle on demand. The LO-Z / HI-Z impedance switch maximizes performance for both low and high resistance headphones, ensuring optimal power delivery and tonal balance. Whether you’re fine-tuning for a specific track or tailoring your signature sound, the GR70 offers total control in an easy-to-use interface.

PREMIUM BUILD AND COMPACT DESIGN

The Fosi Audio GR70 features an all-metal chassis crafted from CNC-machined aluminum alloy, ensuring robust durability, superior heat dissipation, and a premium feel. Its sleek matte black finish and exposed vacuum tubes create a visually striking aesthetic that complements any audio setup. Despite its powerful tube-based circuitry, the amp maintains a compact form factor, making it an ideal centerpiece for desktop audio rigs or smaller Hi-Fi systems. The straightforward layout, extra vents to keep out dust as well as heat, and quality controls provide excellent user experience and long-term reliability.

Specifications

Brand Name
Fosi Audio
Model Name
GR70
Tube Configuration
2× 6AC7 power pentode tubes, 2× 5654 driver tubes
Inputs
1× RCA line input
Outputs
1× RCA pre-out, 3.5mm headphone jack, 6.35mm headphone jack
Power Output
Low Gain: 67mW @ 32ΩHigh Gain: 830mW @ 32Ω
Headphone Impedance Support
LO-Z: 16Ω – 120ΩHI-Z: 120Ω – 300Ω
Frequency Response
20Hz – 20kHz (±1dB)
Signal-to-Noise Ratio (SNR)
≥ 97dB
Dynamic Range
≥ 97dB
THD+N (Total Harmonic Distortion + Noise)
≤ 0.5% (headphone output) ≤ 0.26% (RCA output)
Power Supply
12V DC, 3A
Chassis
CNC-machined aluminum alloy
Dimensions
46 mm (H) × 192 mm (W) × 129 mm (D)
Weight
900 g

Box Content

    What will you get
  • 1x Fosi Audio GR70
  • 2x 6AC7 vacuum tubes
  • 2x 5654 vacuum tubes
  • 1x Pair of Tube Covers
  • 1x 12V/3A power supply adapter
  • 1x User manual

Warranty

1 YEAR WARRANTY

Don't worry, Fosi Audio G70 comes with a 1 Year warranty against manufacturing defects. We guarantee that every product on Concept Kart is genuine and backed by the Manufacturer's warranty.

Read more about Concept Kart's warranty policy.

Shipping Policy

FREE SHIPPING ON ALL PREPAID ORDERS

We usually ship orders on same day if ordered before 2 pm or within 24 hours if ordered later (except on holidays/sunday, where processing times may be higher) from one of our domestic warehouses based out of Delhi. It normally takes around 1 to 5 business days for delivery. We use premium service partners such as Blue dart, DTDC and Delivery for faster and reliable service. A tracking number will be provided upon shipment.

In very rare cases when order is not received after 10 business days of shipment (extended by number of days when the govt. Restricts movement of goods due to factors such as coronavirus pandemic), please contact us and we will provide you a support.