History & AcknowlegementsIn mid-2008, after having successfully developed and released a whole range of high quality headphone amplifier and power amplifier projects to the DIY community, I thought that time is ripe for me to venture into something different. I had been interested in doing a DAC project for some time and this was a good time to start.
Coincidentally, MisterX began emailing me some DAC ideas, and we started throwing schematics at each other. Although my original plan was to design a high-end DAC, I thought it made sense to first do a miniature, high-performance DAC that could be built relatively inexpensively. This would provide valuable DAC design experience that should help with a future high-end DAC project, and also fill a void in the DIY DAC niche.
The γ1 project was thus born. It morphed from a simple USB DAC based on a PCM290x chip, into a much more modular, configurable and full-featured design spanning two circuit boards. Despite this, we kept the build cost reasonable and made careful considerations about parts availability and ease-of-build. Housed in the small Hammond case, not only would γ1 be an excellent functional and aesthetic companion to the Mini³ headphone amplifier, much of Mini³'s design philosphy carried over to the γ1. Just like the Mini³, γ1 would be a highly-integrated. We chose the same Hammond extruded case and all jacks, switches, etc., are board-mounted with no wiring. Through-hole parts are used everywhere except for the integrated circuits, Where available, we chose the easiest-to-solder variants of the chips, in order to keep γ1 as builder-friendly as possible. γ1 must also be good enough for use in home, portable and computer audio applications and be a genuine upgrade to the internal DACs of many devices.
MisterX and I worked on the design at a fast pace over several months and arrived at something we are both very happy with. Not only does it meet all of our design goals, we feel that we have accomplished an artful blend of small size, dense packaging, functionality, buildability, performance and low cost. The two boards fit together like a jigsaw puzzle, filling the small Hammond case with little room to spare, yet each board remains sensibly laid out without being compromised.
We announced the project to the community (at the headwize forum, now defunct) in August 2008, and solicited very useful feedback from various members. Most of these were incorporated into our design, and in October 2008 we launched a prototyping effort and signed up a dozen people around the world to build, evaluate and comment on the design. Prototype boards were sent to the team in late October. A number of issues were identified and corrected. Meanwhile MisterX and I did extensive testing of our prototypes in various configurations, including power-up sequencing, signal/pulse quality on the S/PDIF and I²S lines, and other performance metrics such as frequency response, noise floor, THD/IMD, stereo crosstalk, etc. Some changes were made to the circuit and the improved production boards became available in December 2008. In April 2009, the "full++" configuration using the Box Enclosures B2-080 case was added.
I would like to thank MisterX for being a great project partner. Thanks also go to people who contributed to the γ1 design discussions in the forums, and to those in the prototype team for being enthusiastic and for providing useful comments. You made your mark in this project and its success is yours too:
cetoole, cobaltmute, dougigs, dsavitsk, error401, gjorgi, heady, JamesL, jar, kklee, Mazuki, royewest, runeight, ruZZ.il, srserl
(Hope I didn't miss anyone...)
Look for more exciting DIY projects from AMB in the future!
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