History & AcknowlegementsAfter the successful launch of the γ1 modular miniature DAC in late 2008, MisterX and I were throwing around some ideas about an "expansion board" for the γ1, in order to push the modular concept farther into the high-end. The addition of the γ1 Full++ configuration in early 2009 and its use of the Box Enclosures B2-080 casing led to one logical conclusion -- create a new plug-in board on top of the γ1. Simple upgradability from the γ1 to the γ2 was also achieved with this solution. Thus, the γ2 project was born.
After looking around at various chip options, we went back to Wolfson and chose their top-tier DAC. Coindentally, Wolfson announced the release of the WM8742 at the same time, so we included support for all three of the family -- the WM8741, WM8742 as well as the WM8740. MisterX and I exchanged many iterations of schematic diagrams and circuit board layout files, and found that we also have room for an ASRC chip and a proper analog output stage -- but just barely. Despite the ample amount of board space available, only certain portions can be populated with parts, and with varying height restrictions so that γ2 parts would not bump into γ1 parts when the two are mated together. This proved daunting because we also needed to lay out the board with sensible trace routing, preserving signal integrity, minimizing ground plane current loops, and other aspects in mind. The solution was to go to three copper layers. This allowed both the top and bottom ground planes to be as contiguous as possible. It made the board a little more expensive, but well worth it.
What we also considered was ease-of-build. The DAC and ASRC have fine lead pitch and there is little we could do about it without going to lesser chips. But we made the rest of the circuit as easy to build as possible by using all through-hole parts except the integrated circuits -- the same philosophy adopted for the γ1 and Mini³. Just like these projects, the γ2 would be highly-integrated. The design has a specific target enclosure, and all jacks, switches, etc., are board-mounted with no wiring.
Finally, we also considered the cost. While γ1 has the very high "bang for the buck", we believe the γ2 (with only modest cost increment over the γ1) achieves even greater price/performance ratio. It could stand proud amongst commercial DACs in the $1000+ range.
The project was revealed to the community in June 2009, and shortly after that we launched a prototyping effort and signed up fifteen people around the world to build, evaluate and comment on the design. Meanwhile MisterX and I did extensive testing of our prototypes in various configurations. A few minor physical fitment issues were identified and corrected, but the circuit required no changes and performed flawlessly. Some changes were made to the layout to improve the fit, and the production boards became available in September 2009.
I brought my γ2s to the August 2009 Norcal head-fi meet, and they were very well received. A few people told me that the γ2 + β22 combination was the "best sound at the show".
I would like to thank MisterX for being a great project partner. Thanks also go to people who participated in the γ2 discussions thread 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:
akcrusier, amc, digger945, dude_500, fordgtlover, jnewman, komi, Lifthanger, linuxworks, m1abrams, MrSlim, nattonrice, oneplustwo, TeraHz
Look for more exciting DIY projects from AMB in the future!
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