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Original DAC designs and schematics

Power Supply Unit Rev 3.1

  • Board size - 100×100 mm
  • AC outputs - Up to 3 AC outputs, including one center-tapped winding
  • DC outputs - Up to 3 DC outputs, rectified, unregulated (raw DC)
  • Compatibility - DAC Rev 1.x only

⚠️ Warning! This PSU operates with high voltage (220–240 VAC). Working with high voltage can be dangerous and may result in serious injury or damage if handled improperly. This design is intended for users who are familiar with electrical safety and DIY electronics. Always ensure proper insulation, grounding, and safe assembly practices.

Linear Power Supply Rev 3.1 for DAC Projects - Overview

PSU Rev 3.1 is a transformer-based power supply unit designed specifically for DAC revision 1.x projects presented on this website (see "DAC Revisions and Power Design" in the about section for details).

The design uses two independent PCB-mounted analog transformers to provide dedicated isolated supply rails for DAC sections. It provides AC outputs, as well as unregulated rectified DC outputs when required.

The PCB is a 2-layer board with dimensions of 100 × 100 mm, making it easy to integrate into compact custom enclosures as well as the DacBox S60-A enclosure.

PSU Rev 3.1 assembled board connected to White DAC Rev 1.2

Input Stage and EMI Filtering

The input stage includes a basic C-L-C EMI filter. This helps reduce high-frequency noise from the incoming AC line and prevents interference from propagating into the rest of the system. It provides a practical level of filtering suitable for DIY audio applications.

Two separate fuses (F1 and F2) are used for each transformer.

Transformer Configuration

The board is designed to support two PCB-mount transformers, each in the low-power range (typically around 5-7 W), allowing flexible configuration depending on the project requirements.

Using two separate transformers helps isolate supply domains and reduce interaction between different sections of the DAC system.

Transformer outputs can be configured depending on the application:

  • Transformer T1 (A) - symmetrical (bipolar) AC supply (e.g. 15–0–15 VAC) for analog stages
  • Transformer T2 (B) - single or dual secondary AC outputs (e.g. 7–9 VAC or 2 × 7–9 VAC) for digital and analog circuitry

In most cases, Transformer T2 (B) can use a single secondary winding. However, some projects (e.g. Black DAC Rev 1.1) may require two independent 7–9 VAC outputs, so a transformer with dual secondary windings must be used instead.

PSU Rev 3.1 schematic

Rectification and Power Distribution

The PSU Rev 3.1 provides both raw AC outputs and rectified DC outputs.

Transformer outputs are routed directly to output connectors, allowing AC supply to be delivered directly to DAC revision 1.x boards.

The same outputs can be routed through rectification stages when required. Three diode bridge rectifiers are used, followed by electrolytic capacitors for smoothing.

For the bipolar supply, Transformer T1 (A), the 15–0–15 VAC winding is fed into a bridge rectifier to generate a dual-rail DC supply.

For Transformer T2 (B), its secondary outputs are rectified separately, allowing flexible usage depending on project requirements.

PSU Rev 3.1 PCB

Usage Notes

  • This PSU provides both AC and DC outputs, ensure correct connection depending on the target DAC board
  • Verify transformer wiring, pinouts and output voltages before powering the system
  • Ensure proper insulation and safe handling of mains voltage
Published on 7 May, 2026