Product Overview

The V3 is a high-performance stereo audio power amplifier developed by Fosi Audio based on user needs. It features Texas Instruments’ high-end TPA3255 digital amplifier chip, supporting up to 600W of output power
(into 4Ω impedance speakers). The V3 comes with an innovative design in that there are cooling vents on top and bottom of the aluminum alloy chassis, and the amplifier chip’s heat sink is attached to the casing, turning
the entire chassis into a heat dissipator. This significantly enhances heat dissipation performance, ensuring chip stability and safety, and providing solid support for continuous high-power output. The V3 also integrates
numerous HiFi class capacitors, inductors, and resistors to ensure stable and pure high-fidelity audio output. Furthermore, the V3’s op-amps are replaceable, allowing you to easily swap different op-amps for a
personalized music experience. The V3 is a mini amplifier designed for music enthusiasts, and we believe
it will take you on a wonderful journey through HiFi music.

Product Specifications

Audio Channel2
Power Amplifier ChipTI TPA3255
Input InterfaceRCA In
Output InterfaceSpeaker Output (Banana Plug or Bare Wire), Pre-Out
Dynamic Range≥110dB
Terminal Impedance2~8Ω
Output PowerMax 300W x2@4Ω
Frequency Response20Hz-20kHz (±0.1dB)
Input Voltage RangeDC 24V~48V

Package Contents

V3 Power Amplifier ×1
Power Supply ×1
User Manual ×1

Quick Steup

Do not plug in the power cord until all connections are complete.
Step 1: Prepare your audio source device, V3 power amplifier, 24V-48V power adapter, passive speakers, speaker cables (with banana plugs or bare wires), and RCA audio cable;
Step 2: Plug the RCA cable into the RCA input terminal of V3, red for right channel and white for left channel. Connect the other end to your audio source device;
Step 3: Connect the speakers to the V3’s speaker terminals with the speaker cables, ensuring the polarity is matched correctly. The red is the positive pole, while black is the negative pole. You scan the QR code to
watch the instruction video;

Step 4: Plug the power adapter connector into the DC power input port of V3, and power cord into an AC outlet;
Step 5: Turn the knob clockwise to switch on the V3, and the red power indicator light will be on. Then you can play songs on your audio source device and start enjoying music.
NOTE: The pre-out terminal can be used to connect an active subwoofer, active speakers or a second amplifier to expand or customize your audio system.


01. The system is set up, but there is no sound output. 

• There may be no power. Please check whether the power indicators on the V3 and power adapter are on or not.
• The volume may be too low. Please turn the volume knob clockwise to raise the volume.
• The audio cables may be connected incorrectly. Please follow the instructions above to reconnect the cables;
• The songs in your audio source device may not be played or the sound is muted. Please check on the audio source device.


02. The sound output is abnormal.

• Please ensure the polarity is matched correctly when you connect the speaker cables to the binding posts. The red is the positive pole, while black is the negative pole;
• The speaker cables may not be in good contact. Please try to reconnect or swap the cables;
• The RCA cable may not be in good contact. Please try to reconnect or swap it;
• The V3 amplifier may be overloaded. Please turn down the volume.


03. Cannot play when connecting the turntable.

• The turntable may not have a built-in phono preamplifier. Please check in your turntable’s user manual. You’ll need an external preamplifier to connect your turntable and the V3 to play your record;
• The phono output mode may be incorrect. Generally speaking, there are phono output and line output modes. Please select the line output.


04. Why the device connected to the pre-out is still playing after turning V3 off?

• The pre-out terminal is designed to bypass the amplifier’s built-in power amplification stage. The knob on V3 does not affect the pre-out’s signal output or volume. You need to turn off or modify the volume on the device connected to the pre-out.


NOTE: If you still can’t solve the problems, please scan the QR code to learn more or contact our support team support@fosiaudio.com

Warranty and Maintenance

Fosi Audio pledges to give an 24-month limited warranty and support from the date of purchase. If you encounter any problem when using our product, please contact our support team at support@fosiaudio.com

About Us

Fosi Audio designs and builds innovative audio products with all your music in mind. Great sound, simple but elegant designs, high-quality materials, and truly useful features are what Fosi Audio pursues. We sincerely hope you get as much enjoyment from our products as we’ve had to create them!

Our website:
Amazon store:
Our Youtube channel:
Fosi Audio
Our Facebook page:
Fosi Audio
After-sale Service and Technical Support Email:


Fosi Audio Product’s User Manual:


Fosi Audio V3

2-Channel Stereo Power Amplifier Designed for HiFi Audiophiles

Built-in TI TPA3255 Amp

Enabling superior audio quality and ultra-low distortion across the audio band with Class-D efficiency

Replaceable Op-Amps

Roll the op-amps to get your preferred sound signature.

Logarithmic Taper A Pot

Manage the audio volume in a much finer way suitable for human ear.

Quality Components Integrated

Full of what audiophiles could want inside

Japanese NCC Capacitors 63V/2200uF

Japanese Sumida Audio Inductors

German WIMA Output Capacitors

Japanese ELNA Capacitors

Effective Cooling

Vents on the top and bottom, and whole-body heatsink design enhance air circulation and heat dissipation

Cooling Vents on Top

Cooling Vents on Bottom

Heatsink Attached to Case

Born for HiFi Enthusiasts

A great budget HiFi gear to accompany your turntable, CD player, and speakers.


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Product Details

Max Power Output: 300Wx2 @4Ω


SNR: ≥110dB

Terminating Impedance: 2-8Ω

THD: 0.003%

Power Amp Chip: TI TPA3255

Op-Amp: TI NE5532 x2

Power Supply: 32V/5A, 48V/5A

Input Range: DC 24V-48V

Frequency Response Range: 

Input: RCA
Output: Speaker Output/3.5mm Pre-out

User Manual:                 Download

1. V3 ×1
2. User Manual × 1
3. 32V/5A or 48V/5A Power Supply × 1

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