Overview
The design goal of the Alien DAC project is to create a simple USB DAC based on Texas Instruments PCM2702 chip.
You may consider this project if you are looking to build your own USB soundcard to
upgrade your onboard sound. The project is also a good introduction to DIY SMD soldering and DACs.
The main features are:
- Works on any OS supporting USB streaming audio: Windows, Mac OS, Linux.
- Board size: 45.4mm x 50.5mm - fits Hammond 1455C enclosure.
- 4 distinct powering options. Can be made USB-powered.
- All parts are easy to get from either Farnell or
Digikey.
- Supported by the DIY community.
Design
Current Status
Alien DAC v1.1 PCB Group Buy at head-fi.org is now open. Read the group buy rules carefully before ordering the boards.
History
The initial design specs were to supply power from a small, light battery pack consisting of 2 x NiMH cells
fed through a small switching DC-DC converter to provide an unregulated 5.3V output (Maxim MAX1722).
This output was regulated to the +5V and +3.3V required by the PCM2702 using two LDO Texas Instruments REG102
fixed output regulators.
Revision A brought a few improvements:
- The power supply stage was revised to allow powering straight from the USB plug.
- An additional decoupling capacitor on the 3.3V line.
- The use of 1206 resistors in place of the smaller 0805s.
Revision B started as a simple modification of the board.
A few days later it turned into a 6 week re-design spree.
The following list reflects some of changes worth mentioning:
- MAX1722 was replaced with TPS6734 and LM317.
- The layout around PCM2702 was carefully revised to minimize noise.
- Ferrites were added to suppress EMI.
- The ground plane was moved to the top and the traces to the bottom.
- All non-electrolytic capacitors were changed to SMD.
- All SMD capacitors and resistors were changed back to the 0805 package.
- Improved power regulation.
- A new option to power the DAC from a virtual ground amp.
- The board now fits Hammond 1455C enclosure.
- Mounting holes in each corner.
Alien DAC v1.0 introduces a few changes following the Revision B feedback:
- TPS6734 and LM317 were removed.
- Improved the layout to minimize noise even further.
- Additional CLC filters on VBUS and ground.
Alien DAC v1.1 is a cosmetic update following the Alien DAC v1.0 feedback:
- Adjusted silk and stop masks.
Links
