Portable USB Hi-Fi Headphone Amplifier

This is a USB portable headphone amplifier design based on CT7601SR + ES9018K2M, supporting PCM 32bit/192kHz and DSD audio playback.
Version update history:
V1.0: Initial verification version
. V2.0: 1) Reduced board size;
           2) Replaced the headphone amplifier IC from MAX97220 to SABRE9601K, which works better with the ES9018;
           3) Added dual-color LEDs for audio format display;
           4) Fixed the bug of reversed left and right channels in the headphone jack.
Detailed design parameters are as follows:
CT7601SR is chosen as the USB interface chip, which is inexpensive (approximately 20 RMB/pcs), driverless, supports up to 32bit bit depth, and up to 192kHz sampling rate, meeting the needs of modern digital audio;
The DAC uses ES9018K2M, with 127dB SNR, supporting up to 32bit/384kHz PCM audio and DSD 128 direct bitstream audio (limited to 32bit due to the USB interface chip). (192kHz PCM and DSD64);
The headphone amplifier chip uses the SABRE9601K, which has a higher signal-to-noise ratio and higher fidelity compared to the MAX97220 used in the V1 version. It is powered by a single power supply, making it suitable for portable applications.
The 4-layer board design uses optimized components and circuit layout to fully realize audio performance.
The shell size is 52mm*20mm*8mm, which is small and easy to carry.
A shell model file is provided for 3D printing, which is aesthetically pleasing and can better protect the PCBA from damage.
Actual product image:
Front
and back.
Connect the headphone amplifier to the computer. The LEDs on the back of the board will light up. The LEDs are blue during idle and PCM audio playback, and green during DSD audio playback.
 
 
Important note:
The CT7601 requires firmware flashing to function properly. The following instructions will explain how to flash the firmware via DFU (firmware tool attached).
1. First, install the following two drivers (abbreviated as 0ea0 and 2fc6):
    Comtrue-inc_Firmware_Update_Device_0ea0
    Comtrue-inc_Firmware_Update_Device_2fc6
2. Open "ISP-Tool", connect the board to the computer's USB port.
When the right-hand box turns green, as shown in the image below, it indicates that the board has been recognized and you can begin flashing.
3. Click the "File" button, select the firmware to flash (CT7601_ES9018K2M.hex),
and then click the "Auto" button to start flashing. When "Success" appears under "Status" at the bottom, the flashing is successful.
4. After flashing is complete, the computer will automatically recognize the USB DAC and it will be usable (Win10/11 only).