This project is first in a series of hobbyist-designed digital-to-analog converter projects, built around the well-known delta-sigma CS4398 chip from Cirrus Logic. The goal was to create a flexible, good-sounding DAC with a primary USB input option and a reasonably compact PCB that accepts AC power supply directly from an analog transformer.

The DAC is designed as a standalone unit that can handle both S/PDIF and USB audio inputs. It combines a classic, proven CS4398 chip, MCU-based control via the I2C bus and direct integration of a USB transport module. For S/PDIF input, the design uses the CS8416 receiver in hardware configuration. The CS8416 chip handles coaxial input and feeds the decoded audio data to the DAC chip via a 74HC157 multiplexer. USB input is implemented via direct mounting of an Amanero Combo384 module, or its analogs, onto the PCB. This avoids extra wiring and helps keep signal paths short and clean. It also makes the board more compact and easier to assemble.

Some components are optional for MCU and/or STA modes. Please refer to the provided BOM for details.

C54 and C56 are not installed. C55 and C57 are replaced with 0 Ω resistors (1206 or 0805), or can be shorted with solder jumpers. NB: In the provided Gerber files, this connection is already implemented, so no jumpers are required for newer PCBs.

White DAC Rev 1.2 supports PCM rates up to 192 kHz / 24 bit. It is not possible to provide a 384 kHz stream to the CS4398, if so - the chip remains in a reset state when such a stream is applied. The output relay stays off, so no output noise appears. The Amanero Combo384 manufacturer also claims that custom configuration with a maximum of 192 kHz is possible, see details here

Both DSD64 and DSD128 supported in MCU control mode. The DSD mode is selected based on D64 USB module pin, i.e. DSD64 for "L" pin state and DSD128 for "H" pin state.

The CS4398 DAC chip has differential voltage outputs, so only a low-pass filter (LPF) is needed to remove high-frequency noise from the DAC output. The analog output stage includes a classic Butterworth LPF topology based on DIP-8 dual op-amps, such as NE5532, LM4562, or similar. Following the filter, a Class A buffer stage based on npn and j-fet transistors provides impedance matching and stable output drive. I prefer using BC547 and SK117 pairs here. The output is protected by a standard signal relay (e.g., Omron G6S-2), which helps prevent unwanted pops or transients during power-up and input switching.

The board supports direct mounting of Amanero-style USB-to-I2S modules and also provides a coaxial S/PDIF input based on the CS8416 receiver. Source selection is handled by DD3 (74HC157 multiplexer) and DD6 (74HC00 logic). By default, USB input has priority. When a USB interface is connected and powered, the DAC receives I2S from USB. Otherwise, the S/PDIF input is used.

An onboard MCU STM32F030F4 manages the digital control logic. It monitors the incoming PCM sample rate and automatically configures the CS4398 operating parameters, including oversampling (OS) settings. This removes the need for manual configuration and makes the DAC much more user-friendly. The White DAC Rev 1.2 schematic allows both MCU and stand-alone (STA) modes control, but for STA there are some restrictions - no OLED display, no frequency detection and thus no automatic OS bit configuration, no DSD support. Please note this when choosing between MCU and STA modes.

DAC modes are set using the XS9 jumper:

Jumper XS8 is used only for STA mode and controls OS settings

The PCB is a two-layer design with overall dimensions of 115 × 100 mm. The layout is optimized for compact routing and practical assembly, with a minimum track width of 0.22 mm and a minimum via drill diameter of 0.4 mm. For mechanical mounting, it is recommended to use 18-20 mm spacers for the main PCB and 12 mm for the USB interface module.

The board is designed to be powered directly from AC sources, following standard linear supply practices. The required transformer outputs are 2×15 VAC for the analog stages (I/V and LPF) and 9 VAC for the digital and analog sections.

An additional configuration option is provided for the DAC chip analog supply (DA1 regulator). This rail can be sourced either from the dedicated +12 V LPF supply or from the shared +9 V supply line. Selection is done via J1/J2 solder jumpers located on the bottom side of the PCB. In practice, I prefer using the shared +9 V supply for the DAC analog section. This keeps the LPF stage supply isolated and avoids introducing additional load or potential coupling into the analog filtering stage.

CS4398 is often described as having a smooth and slightly warm presentation, without sounding overly analytical. Its sound is characterized by a natural midrange and non-fatiguing treble, which makes it easy to listen to for long sessions. To summarize my experience, the CS4398 can be considered a "musical" and detailed DAC rather than a strictly clinical one. From a subjective standpoint, the CS4398 remains an enjoyable chip. The sound is clean and comfort without being overly sharp, which makes it suitable for long listening sessions, like YouTube streaming or background music.

I hope this starter project can help anyone with basic DIY experience reproduce or modify the design. Good luck!