Open Source DAC

Henry Audio USB DAC 128 mkII is an open source digital-to-analog converter for computer audio. This page links to discussion forums for DAC users and to development resources.

User Communities

DAC user forums are available in multiple languages. You are more than welcome to ask questions about the DAC and view what other owners have written about it.

Instructions and Manuals

To learn about the DAC and how to use it you should first read the Fact Sheet. It contains:

  • Technical Specifications
  • USB Audio Class 1 and 2 Information
  • Windows Install and Uninstall Instructions
  • Open Source Schematic Files

If you wish to dive into the technical details you should first read the Audio Widget Readme file. The file starts of gently and goes into great technical detail about how the Audio Widget technology works. The file contains:

  • Project introduction and history
  • Listening to audio UAC1
  • Listening to audio UAC2
  • Installing drivers
  • Installing players
  • WidgetControl software
  • Installing new firmware
  • Compiling new firmware
  • Modding the hardware
  • Modding Windows drivers
  • Appendix 1 - git primer
  • Appendix 2 - UAC2 Feedback Mechanism


Click the thumbnails below to get larger pictures.

DAC Rear Side

DAC Rear Side

DAC Internals

DAC Internals

Links and Resources

The open source Audio Widget project and its origin, the SDR Widget project, use various webpages to stay in touch and store project data.
Feel free to join the project! Important web pages are found here:


Q: Do I have to be a programmer to use the USB DAC 128 mkII?

A: No, you don't! It plays music right out of the box. But it is made to be tweaked by those who wish to.

Q: Do I have to be an analog hacker to use the USB DAC 128 mkII?

A: No. But if you have a soldering iron you can tweak it. Although it works very well, it is designed as a starting point for DIYers.

Q: I am a programmer. Where do I start?

A: Visit the project links above and join both SDR-Widget and Audio-Widget mailing lists. There is very little cross-posting. The SDR-Widget Wiki is a good starting point. It explais the git repository and other details.

Q: Which coding efforts are wanted?

A: The MCU firmware is stable. But there may be features you need which we haven't thought of. Our most pressing issue right now is Windows driver support. If you're familiar with Audio processing / USB / Windows drivers / Linux drivers, or related things, please join our efforts.

Q: I like analog tweaking. Where do I start?

A: The Henry Audio USB DAC 128 mkII is a good starting ponint for analog tinkerers. Feel free to mod it! Please feed your knowledge back to the group members.

Q: I'd like to reuse the PCB designs for a commercial project. What do I do?

A: Contact me at I have years of experience in commercial PCB design and manufacturing. We'll sort something out!

Q: The diyaudio thread is huge. Where do I look?

Capacitors posts 670, 756, 763, 854, 867
Linux player posts 758-759, 800
Layout, back panel posts 819, 825, 831
Test results post 819 currently evolving...
Jtest posts 761, 776, 781 currently evolving...
Feel free to suggest other highlights!!

Obsolete Kits

The predecessors of the AB-1.2 are called AB-1 and AB-1.1. These kits are no longer for sale. If you own one, consult these web pages for information about your system. If you don't own one you may ignore these links. AB-1 AB-1.1

Design & code by Found.

Photography by Dag Dalvang