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Project Specification — STM32F407 PCM1795 Hi-Fi DAC Card

Project Overview

Status: Draft schematic rebuilt at IC level.
Purpose: High-precision hi-fi DAC card using PCM1795, 3× OPA1612, low-noise LT3042 DAC rails, and external LT3045/LT3094 ±12 V op-amp rails.
Design priority: Minimum noise and distortion over cost, compactness, or convenience.

Current Schematic Direction

The project is no longer only a connector/interconnect draft. It now contains the actual IC-level schematic blocks:

PCM1795DBR 28-pin SSOP DAC.
U2/U3 OPA1612 I/V conversion stages.
U4 OPA1612 differential-to-single-ended output/filter stage.
LT3042 3.3 V digital DAC rail and LT3042 5 V analog DAC rail.
8-pin power input header for raw DAC regulator inputs, ±12 V OPA rails, GND, and AGND.
RCA left/right output connectors.

Main Signal Chain

Diagram

Key Component Values

Table

Function	Value
I/V feedback RF	680 Ω 0.1%
I/V feedback CF	47 pF C0G/NP0 starting value
I/V non-inverting bias	680 Ω to AGND
Differential output network	10 kΩ 0.1% matched resistors
Differential HF cap	220 pF C0G/NP0
RCA output isolation	100 Ω series
Optional output RF shunt	2.2 nF
I2S/SCK damping	27 Ω starting value
PCM1795 digital rail	3.3 V LT3042
PCM1795 analog rail	5.0 V LT3042
OPA rails	±12 V from LT3045/LT3094 module

Important Caveat

The library PCM1795 symbol must be visually checked against the TI datasheet before PCB layout because the uploaded datasheet pinout is the authority for physical pin numbers. The schematic uses named pins, but any library symbol/footprint mismatch must be corrected before fabrication.

Next Stage

Before PCB layout, verify the schematic visually in Flux and resolve ERC findings. Then proceed to placement with strict analog layout constraints: shortest I/V paths, DAC/OPA clustering, clean AGND/DGND reference join, and physical separation from I2S/SCK lines.

Project Overview
Current Schematic Direction
Main Signal Chain
Key Component Values
Important Caveat
Next Stage

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