Fosi Audio DAC-Q4 - User Manual

Questions and Answers

S
Sarah SmithJul 29, 2025
How to fix no sound when PC-USB connects to PC with Fosi Audio DAC-Q4?
- J
  Joshua MeyerJul 29, 2025
  If your PC-USB connection to your PC isn't producing any sound with your Fosi Audio Amplifier, first press the PC-USB operation to confirm whether the digital playback output has been selected. Additionally, some computers' USB ports on the front panel may be low quality, so try changing the USB port, preferably using the USB port on the back panel of the computer.
B
Bradley ParkerAug 7, 2025
What to do if Fosi Audio DAC-Q4 Amplifier has noise through USB input without Dolby/DTS audio?
- M
  Michelle GallowayAug 7, 2025
  If you're experiencing noise through the USB input with your Fosi Audio Amplifier, despite not using Dolby/DTS audio, it might be due to unstable data transmission from some USB ports. Try switching the USB port to USB 3.0 or a back USB port and try again. You can also try again with another computer, replace the PC-USB cable and retest. If the original cable is faulty, contact us for compensation. As an alternative, change the power supply adaptation and retest.
S
sotoamyAug 18, 2025
How to enable RCA analog output on Fosi Audio Q4 Amplifier?
- M
  Michael LucasAug 18, 2025
  To get the RCA analog output working on your Fosi Audio Q4, check if the headphone output is plugged into a headphone. If it is, unplug the headset to simulate RCA output.

Summary

Product Overview and Controls

Front Panel Controls

Identifies and describes the controls and indicators on the front of the DAC-Q4.

Rear Panel Ports

Details the input/output connections and power input on the rear of the device.

Quick Setup Guide

PC-Windows Setup

Step-by-step instructions for connecting the DAC-Q4 to a Windows PC via USB.

Troubleshooting and FAQs

White Noise Troubleshooting

Provides solutions for issues causing continuous white noise, often related to audio formats.

The Fosi Audio DAC-Q4 is a compact mini digital-to-analog audio converter designed to enhance your audio experience. It serves as a preamplifier or volume control for PC/MAC/Computer systems, ensuring exquisite musicality, accurate and realistic phasing, and faithful reproduction of the original sound.

Function Description:

The DAC-Q4 features multiple digital inputs, including USB, optical, and coaxial, allowing it to connect to a wide range of audio sources. For output, it provides a classic 3.5mm headphone jack and RCA outputs, making it suitable for most home audio systems. The device incorporates bass and treble controls, enabling users to fine-tune the audio output to their preferences. A multi-function knob on the front panel acts as both a power switch and a volume control. Input selection is managed via a dedicated button, allowing users to switch between USB, optical, and coaxial sources.

Important Technical Specifications:

Input Type: USB, Optical, Coaxial
Output Type: 3.5mm Headphone, RCA
Chipset: SA9023+CS8412+97220+NE5532
USB Sampling Rate: 24Bit/96kHz
Optical/Coaxial Sampling Rate: 24Bit/192kHz
Headphone Impedance: 16-200Ω
RCA Output Level: 2.3V
Power Supply: 5V
THD (Total Harmonic Distortion): ≤0.01%
SNR (Signal-to-Noise Ratio): ≥105dB
Size (LWH): 73.59833MM
Net Weight: 0.4kg

Usage Features:

The DAC-Q4 is designed for straightforward setup and operation.

PC-Windows Setup:
1. Connect the Micro-USB cable to an AC adapter and then to the Q4 for power.
2. Connect the Q4 to your PC via the PC-USB cable.
3. Turn down the volume control to the lowest level (power off) and connect headphones to the 3.5mm jack.
4. Adjust the input mode selection key to USB.
5. Turn on the power switch (turn up the volume). The volume knob also functions as the power switch: clockwise to turn on/increase volume, counter-clockwise to turn off/decrease volume to minimum.
6. Select "Fosi Audio Q4" (Digital HiFi Audio) as the playback device in your computer's sound settings.
7. Open your audio application and enjoy. Note: Always turn down the volume before connecting power to prevent hearing damage.
Optical Setup (e.g., with TV):
1. Connect the Micro-USB cable to an AC adapter and then to the Q4 for power.
2. Connect your TV to the Q4's optical interface using an optical cable.
3. Adjust the input selection button to optical mode.
4. Set the TV's optical output sound to RAW/PCM. Note: The Q4 does not support Dolby or DTS sound. Selecting these formats will result in noise or no sound output. Ensure your TV is set to RAW/PCM.
5. Open your audio application and enjoy.
Coaxial Setup (e.g., with TV):
1. Connect the Micro-USB cable to an AC adapter and then to the Q4 for power.
2. Connect your TV to the Q4's coaxial interface using a coaxial cable (not included).
3. Adjust the input selection button to coaxial mode.
4. Set the TV's coaxial output sound to RAW/PCM. Note: Similar to optical, the Q4 does not support Dolby or DTS sound. Ensure your TV is set to RAW/PCM.
5. Open your audio application and enjoy.

Troubleshooting/QA:

Powering the DAC-Q4: Use the supplied Micro-USB cable and a PC-USB port/5V power adapter. Ensure the Micro-USB cable is not forced into the power port.
Silent RCA Analog Output: Check if headphones are plugged into the headphone output. Unplug them to enable RCA output.
Endless White Noise: Verify that your input device is not using Dolby/DTS audio. Switch off Dolby/DTS audio and retry.
Noise through USB Input (No Dolby/DTS):
- Try switching to a USB 3.0 port or a different USB port, as some ports may have unstable data transmission.
- Try with another computer.
- Replace the PC-USB cable if it's faulty.
- Consider changing the power supply adaptation; an aging power supply can cause abnormal power and white noise. A PC-USB port/5V power adapter is recommended.
USB Device Not Recognized on Windows:
- Go to Device Manager, expand "Universal Serial Bus controllers," uninstall each device, and restart your computer. USB controllers will reinstall automatically.
- If Windows update is the cause, update all Windows components and reboot.
Plug and Play on Windows: Click the sound icon in the notification area, select "playback device," and choose "Fosi Audio Q4" (Digital HiFi Audio).
Spotify Music Playback Issues: Exit Spotify, switch the playback device to the computer's own sound card, open Spotify, confirm it works, then switch back to DAC-Q4 "Digital HiFi Audio."
Highest Resolution (24Bit/96kHz) on PC: Right-click the PC sound icon, open Volume Mixer, click the device/SPDIF icon ("Digital HiFi Audio"), go to Properties, then Advanced, and select 24Bit, 96000Hz.
Intermittent Sound: Switch USB ports (USB 3.0 or another), as some ports have unstable data transmission. Replace the PC-USB cable if faulty.
No Sound with PC-USB: Confirm that the digital playback output has been selected. Restart the computer and re-check device selection in PC sound settings. Use a USB port on the back panel of the computer if front panel ports are low quality.
Device Stops Working: Ensure your audio source, headphones, amplifier, or powered speakers are working correctly. Check all input and output cable connections. Try changing the audio source, output devices, and cables. Verify the power supply is working.

Maintenance Features:

Fosi Audio products come with an 18-month limited warranty on parts and labor from the date of purchase. For any issues, users are encouraged to contact customer support. The company emphasizes high-quality materials and useful features in its designs.