USB Audio Interface PCB Design

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Design a 2-channel USB audio interface PCB (24-bit / 96kHz) for studio use.
CORE REQUIREMENTS:
  • Microcontroller: STM32F411 (USB Audio Class 2.0)
  • ADC: PCM1864 (2-channel, 24-bit, 96kHz)
  • DAC: PCM5102A for headphone output
  • 2x microphone inputs (XLR)
  • 2x microphone preamps using THAT1512
  • Headphone amplifier: TPA6120A2
  • USB-C connector for power + data (USB 2.0 only)
  • 2.8 inch SPI TFT display (ILI9341)
  • Rotary encoder with push button for menu control
  • No wireless modules, no antennas required
POWER DESIGN:
  • 12V input power supply
  • 5V buck converter for analog and system power
  • 3.3V LDO (TLV1117-3.3 or equivalent) for digital section
  • Separate analog and digital power domains
  • Single-point star ground connection
PCB LAYOUT RULES:
  • 4-layer PCB recommended (Top signal / GND / power / GND)
  • Strict separation between analog and digital sections
  • Analog section on left side (XLR + preamps + ADC)
  • Digital section on right side (STM32 + USB-C + TFT + encoder)
  • Keep microphone signal traces as short as possible
  • Place ADC close to preamps
  • Place USB differential pair with controlled impedance (90Ω)
  • Add decoupling capacitors near every IC (100nF + 10uF)
PHANTOM POWER:
  • 48V phantom power generated externally or via isolated DC-DC module
  • Feed 48V to XLR inputs through 6.81k resistors
  • Add filtering capacitors for noise reduction
UI DESIGN:
  • TFT display shows:
    • VU meters (left/right channels)
    • microphone gain controls
    • headphone volume
    • phantom power status
    • simple menu system
MECHANICAL:
  • PCB size: 160mm x 90mm
  • Front panel: XLR inputs, headphone jack, encoder, display
  • Keep connectors aligned for 3D printed enclosure
STYLE:
Clean professional audio interface similar to Focusrite Scarlett internal layout.
Optimized for low noise, minimal interference, and easy prototyping.

flux

I can’t start the schematic/layout execution right now because this account has no available ACUs, so AI design actions are unavailable.
Nothing has been modified in the project yet. The project is still empty with 0 components and 0 nets.
Remaining work once ACUs are available:
  • Create a project specification for the 2-channel USB audio interface.
  • Add and wire the main schematic blocks: STM32F411, PCM1864 ADC, PCM5102A DAC, THAT1512 preamps, TPA6120A2 headphone amp, USB-C, TFT, encoder, XLR inputs, power supplies, phantom power interface, and decoupling.
  • Define analog/digital power domains and star-ground strategy.
  • Set up the 160 mm × 90 mm 4-layer PCB with analog-left / digital-right placement.
  • Route USB D+/D− as a 90 Ω differential pair and keep mic/preamp/ADC routing short and isolated.
  • Run ERC/DRC review and create bring-up, firmware, and regulatory/manufacturing notes.
Once ACUs are available, I can proceed with the full design build.
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